seen in the plan Fig. 3140, _f´_ being in a slide _g´_, which has a
screw _i´_, and hand wheel _h´_, a weighted lever corresponding to _j_
acting against wheel _h´_. In proportion as _f_ and _f´_ are opened out
to admit thick stuff or work, the hand wheels _h_ and _h´_,
respectively are used to screw the screws _i_ and _i´_ into their
respective slides _g_ and _g´_, and thus maintain the weighted levers in
their requisite horizontal positions. The feed rolls _e_ and _e´_ are
carried in slides _c_ and _c´_, and are adjusted to suit the thickness
of the stuff or work by a hand gearing, which consists of the hand wheel
_a_, seen in the plan and in the front elevation, Fig. 3141, which
drives the pinions _b_ and _b´_, which operate screws for the slides _c_
and _c´_, the latter being a left hand screw. The front rolls _e_ and
_e´_ are therefore held in a fixed position, whereas the back ones _f_
and _f´_ may open out under the pressure of the weighted levers _j_, and
thus accommodate any variation in the thickness of the work.
The rate of feed is varied to suit the nature of the work by the
following construction: The friction wheel O and the hand wheel R are
connected by a yoke _q_, Fig. 3142, at the ends of which are the joints
P, Q, seen in the plan, Fig. 3140. Hand wheel R is threaded to receive
the screw S, and it follows that by revolving R, the friction wheel O
may be moved towards the centre of the friction disc N, which would
reduce the velocity with which N would drive O, and therefore reduce the
rate of feed. If the friction wheel O be moved from the position it
occupies in the plan Fig. 3140, to any point on the other side of the
centre of the friction disc N, the direction of feed motion would be
reversed.
A band saw machine for the conversion of logs into timber, and
constructed by Messrs. London, Berry & Orton, is shown in Fig. 3143. The
logs are fixed to the carriage by dogs and the carriage traverses the
log to the feed.
RECIPROCATING CROSS CUTTING SAW FOR LOGS.--The machine shown in Figs.
3144 and 3145 is designed for the purpose of cutting heavy and long logs
into convenient lengths preparatory to cutting the logs up in other
machines, and it is usually therefore placed at the entrance to the
mill, where it is of immediate service as the lumber comes into the
building.
The machine here shown is intended for logs up to 36 inches in diameter,
is simple in construction, requires very little foundation, is easy to
handle, and occupies but very little room.
The saw is here fed mechanically to its cut, whereas in some machines it
is fed by its own weight, and therefore requires great care to be taken,
when the saw is finishing its cut, in order to prevent it from falling
after it has passed through the log.
Fig. 3145 is a side elevation and Fig. 3144 a plan of the machine, in
which A is the frame of the machine on which are the bearings for the
shaft B carrying the fast pulley C, loose pulley D and fly-wheel E at
one end, and at the other, a crank disc F, whose pin is shown at G. This
drives the saw K through the medium of the connecting rod H.
The saw is fast at the butt end to along slide J, J, which works in a
long guide formed on the face of the swinging frame L, which pivots at
one end on the shaft B and at the other is carried by a slide P, on the
vertical slideway M, and is fed down the same to give the saw its cut by
the screw whose hand wheel is shown at N.
V is a second guide for the saw, and being connected to the slide feeds
down with the saw until it meets the log.
A counterweight W balances the weight of the slides and saw, so that
there being a pit beneath the balance weight the saw and its guides may
be raised so that the saw stands out of the way when not in use. Y is a
dog for holding the log, which is also blocked by the wedges Z Z´.
[Illustration: Fig. 3146.]
The construction of the main bearing is shown in Fig. 3146, in which it
is seen that the hub or boss of the loose pulley is much longer than
that of the fast one, thus providing a large amount of bearing surface,
which is advantageous because the belt will remain longer at the loose
pulley than it will on the tight one. The sleeves or bushes in which the
shaft runs afford a simple means of renewal to restore the fit when the
shaft has worn loose in its bearings.
It is obvious that as the guide frame L is pivoted to the shaft B, it
carries the end of the saw (as it is fed down) in an arc of a circle of
which the axis of B is the centre, whereas the slideway M is straight,
and slide P therefore moves in a straight line instead of in the
required arc. Provision however is made to accommodate these two motions
as follows:
[Illustration: Fig. 3147.]
[Illustration: Fig. 3148.]
Fig. 3147 is a sectional view of the slides on the slideway M and Fig.
3148 a plan of the same. The hand wheel N corresponds to N in Fig. 3145.
Upon the vertical slideway (in Fig. 3145) of the standard fits the slide
P, which has a horizontal slideway for the slide R, which is free to
slide automatically, having no screw or other device to restrain it,
save the guide frame L, and therefore as this frame is lowered to feed
the saw the slide R moves automatically to accommodate the arc of a
circle in which the guide moves on account of being pivoted at B.
HORIZONTAL SAW FRAME.--This machine is designed for the more expensive
woods, such as mahogany, and is finding much favor because it will cut
at a very high speed, the saw travelling about 150 feet per minute.
[Illustration: _VOL. II._ =LOG CROSS-CUTTING MACHINE.= _PLATE XXIV._
Fig. 3144.
Fig. 3145.]
[Illustration: Fig. 3143.]
The roughest shaped trunk may be easily fixed on the travelling table,
and a thin saw may be used as it may be very tightly strained. This
machine is used either for breaking down timber, or for converting it
from the log to any desired thickness, the thickness of the boards being
very readily and easily varied.
The machine consists essentially of a framework carrying either one or
two very thin and tightly strained saws operating horizontally and
cutting on both strokes, so that the feed is continuous, the
construction being as follows:
[Illustration: Fig. 3150.]
Referring to Figs. 3149 and 3150, A is a base plate or bed carrying two
uprights or standards B, B, having guideways C, C, for the cross-head D,
which has slideways E, E´, for carrying the frame F, F, which carries
the saw G, which is guided on each side of the work by the guides H, H´.
The frame F, F is connected to the slides J, J´, and has the rod K, to
which the connecting rod pin L is attached, and the rod M, which acts as
a stretcher. A connecting rod P, connects the pin L to the crank pin Q,
on the crank Q´, which is driven by belt from the pulley T, a fly-wheel
being provided at S.
It is obvious that as the crank revolves the saw reciprocates, its line
of motion being determined by the guideways E, E´.
The construction of the saw is shown in Fig. 3151, and it is seen that
for half its length, the teeth are formed to cut when the saw moves in
one direction, while for the other half the teeth slope in the opposite
direction, and are therefore arranged to cut when the saw is on the
opposite or return stroke, and the construction whereby the saw is
enabled to cut on both strokes is obtained as follows:
[Illustration: _VOL. II._ =HORIZONTAL SAW FRAME.= _PLATE XXV._
Fig. 3149.]
Referring to Fig. 3149, the two slides E, E´, on which the saw-carrying
frame F F slides, are not in line or parallel one with the other, but
each slide is at an angle of about 85 degrees to the line of feed, so
that as frame F is reciprocated at each stroke, one end of the saw
advances towards the cut, and the other recedes from it, thus causing
the saw to cut first on one half and then on the other of its length,
one half cutting on the forward, and the other on the return stroke.
[Illustration: Fig. 3151.]
The studs or saw-buckles for attaching the saw to the frame are shown in
Fig. 3151, in place on the ends of the saw, the part I, that fits in the
frame F, Fig. 3149, being squared so that the saw cannot be twisted in
tightening up the nuts of the saw-buckle.
The belt works for driving the saw are arranged as follows: at T are the
fast and loose pulleys for driving pulley R, the belt passing from T
over two pulleys (shown dotted in, Fig. 3149), U, U´, whence it
stretches to the crank driving pulley R, whose bearing is provided on
the cross-head, so that the two move together when the cross-head is
altered in height from the work-table or carriage, to accommodate
different thicknesses or diameters of logs.
It is obvious that in proportion as the cross-head is set nearer to the
carriage, the belt from T to U, U´ would become slack; provision is made
however, to prevent this as follows:
Pulley U, is carried on a frame or swing lever X, to which is attached
by rope V the weight W, which therefore regulates the tension of the
belt.
The cross-head D may be raised or lowered by belt power or by hand, as
occasion may require, the usual course being to move it to nearly the
required position by belt power, and then complete the adjustment by
hand, a graduated scale being provided as shown, whereby the rack can be
set to cut the required thickness of plank without measuring the timber.
The belt motion for raising or lowering the cross-head is obtained by
the pulleys at Y, the wheel for the hand adjustment being shown at Y´.
In either case the bevel gear wheels Z, Z´ operate, respectively, a
vertical screw engaging a nut on the cross-head.
The log feed is obtained by a motion separate from the return motion,
there being three rates of feed and a quick return motion, the
construction being as follows:
Referring to Figs. 3149 and 3150, a is a belt pulley fast on the crank
shaft, and driving pulley _b_, which is also shown dotted in. Pulley _b_
drives the vertical shaft _c_, on which is the cone pulley _d_, having
three steps, and which drives (by means of belt _d´_) cone pulley _e_,
on which is a worm _f_, driving the worm wheel _g_, which runs idle on
its shaft unless engaged therewith by means of the clutch _h_. The shaft
of worm wheel _g_ is omitted in Fig. 3149, so as to leave the
belt-shifting mechanism for pulleys _q_, _q´_ exposed to view. On this
shaft however is a pinion driving the gear wheel _k_, on whose shaft is
a pinion _l_, driving the gear _m_, which engages the rack _n_, on the
under side of the carriage.
The clutch _h_ is engaged by the lever _i_, to the upper arm of which is
attached the rod _j_, _j_, from the lever _p_, hence operating _p_
(which is done by hand), back and forth, throws clutch _h_ into and out
of gear with the worm wheel _g_, and puts the carriage feed on or throws
it out, according to the direction in which _p_ is moved.
The upper end of shaft _c_ is carried in a bearing on the cross-head,
and is provided with a featherway or spline, so that as the cross-head
is raised or lowered the upper end of _c_ passes through its upper
bearing, and the pulley _b_ travels with the cross-head. The three rates
of carriage feed are obviously obtained by means of the three steps on
the cone pulleys _d_ and _e_.
We have now to explain the construction of the mechanism for traversing
the table back, and giving it a quick return motion, or in other words a
quicker motion on the back than on the feed traverse, and this is
arranged as follows:
_q_, is a fast and _q´_, _q´´_, are loose pulleys, one driven by an open
belt _r_, Fig. 3150, and the other by a crossed belt _r´_, from a
countershaft. The belt-shifting forks are operated by lever _s_, whose
upper end engages with the rod _t_, which is operated by the lever _u_.
The loose pulleys _q´_ and _q´´_ are twice as wide as the fast pulley
_q_.
Now suppose that lever _u_ is moved to the right, and the belt would be
moved from the loose pulley _q´´_ to the fast pulley _q_, while the
other belt would merely be moved or shifted from one to the other side
of loose pulley _q´_.
Similarly if lever _u_, be moved to the left, the belt on the loose
pulley _q´_ will be moved on to the fast pulley _q_, and the belt on
pulley _q´´_ would simply be moved across the face of the pulley, and as
the countershaft pulleys for the two pulleys are of different diameters,
therefore two rates of motion are obtained.
The shaft _v_, on which pulley _q_ is fast, drives the pinion _l_, which
drives _m_, the latter gearing with the rack beneath the carriage.
The carriage is guided by the wheels _z_, which are secured to it, and
run on the iron guideways _z´_, the flanges of the wheels preventing
side play, and causing the carriage traverse to be in a straight line.
WOOD-PLANING MACHINES.
[Illustration: Fig. 3152.]
The simplest form of planing machine for wood work, is the hand planer
or buzz planer, as it is termed, an example of this class of machine
being shown in Fig. 3152, which has been designed and constructed by
George Richards, for the use of pattern-makers.
It consists of a frame carrying a revolving shaft, which is by some
called the _cutter head_, and by others the cutter bar, and to which the
cutters or knives are attached.
The work is rested upon the work table, or else pressed against a guide
or _fence_, and fed by hand over the revolving knives, whose cutting
edges protrude above the surface of the table, to the amount of the
depth of cut it is intended to take.
[Illustration: Fig. 3153.]
In this example, however, the table is made in two sections, the front
one of which is below the cutter edges to an amount equal to the depth
of the cut, and the back one level with the cutter edge, when the latter
is at its highest point in its path of revolution, the construction
being shown in Fig. 3153, in which J, J, represents the top part of the
main frame of the machine, C the cutter head, B the front or feed table,
A the back or delivery table, and W a piece of work being fed in the
direction of the arrow.
Upon the upper surface of the frame J, J, and on the feed side of the
cutter head is the carriage G, to which are pivoted two links L, L,
which support the feed table B. At D is a hand wheel whose screw has
journal bearing in a lug from the table, while the screw threads into a
nut provided in the carriage. Obviously then by operating the hand wheel
D, carriage G is moved along the top of the frame J, and the height of
table B is adjusted. Thus if the carriage G is traversed to the left,
the link L would fall more nearly to a horizontal position, and table B
would lower. Or if G were moved to the right, links L would stand more
nearly vertical, and table B would be raised, it being understood that
table B is not permitted to move endways. Similarly by means of hand
wheel C, carriage H may be moved to adjust the height of table A.
By this construction, the work can bed fairly on the delivery side, as
well as on the feeding side of the cutter head, which is not the case
when a single table is used.
It is obvious that the work must be fed in opposition to the pressure of
the cut, which endeavors to push the work back from the cutter, and this
limits the size of work that the machine can operate upon.
[Illustration: Fig. 3154.]
The work can be fed easier however, with a cutter skewed or set out of
line with the axis of the cutter head. Thus in Fig. 3154, is the common
form of cutter head, carrying two knives placed diametrally opposite, so
that the weight of one counterbalances that of the other, and the head
will therefore run steadily and smoothly. The knives K, K´ are here set
parallel with the axis of the cutter head, hence the whole length of the
cutting edge meets the work at the same instant, and a certain amount of
time must pass after one cutting edge has left the work before the other
cutter edge meets it.
[Illustration: Fig. 3155.]
This is remedied by the construction of cutter head shown in Fig. 3155,
in which three cutters are used, and each cutter is set askew, or out of
parallel with the axis of cutter head, so that the knife begins to cut
at one end, and the cutting action gradually extends to the other, hence
the cutting action is more continuous and uniform, and better work is
produced, while less power is required to drive and feed the machine.
[Illustration: Fig. 3156.]
Fig. 3156 shows a cutter head with two skew cutters.
The cutter head is provided with a cover or guard, which is arranged as
follows: In the table is cut a groove or slideway, in which a slide
fits, and to this is attached a thin sheet-iron guard. To the slide is
attached a weight, which draws the guard back to the fence after the
work has passed over the cutter head. By this means the guard covers all
the knife edge that protrudes beyond the work, no matter what the width
or thickness of the work may be; the guard can however be fixed in
position when a number of pieces of the same size are to be planed.
The fence provides a guide surface for the work, and its face may be set
at any required angle to the surface of the work table. Suppose, for
example, that the sides or edges of a piece of work require to be at an
angle of 100 degrees to the top and bottom surfaces, then the top
surface may be planed first, and the fence being set at an angle of too
degrees to the table surface, the top of the work may be pressed to the
surface of the fence while fed across the cutter, and as a result, the
side or edge will be planed at 100 degrees to the top.
ROLL FEED WOOD PLANING MACHINE.
[Illustration: Fig. 3157.]
Fig. 3157 represents a roll feed wood planing machine, designed and
constructed by George Richards & Co., of Broadheath, near Manchester,
England, the construction being more fully shown in the detailed figures
following. The machine consists essentially of a framework, carrying a
cutter head with two knives, and having a pair of feed rolls, in front
and a pair behind it. The front pair feed the timber to the cutter head
and the back pair deliver it from the cutter head.
[Illustration: Figs. 3158, 3159.]
Each pair of rolls is geared together, so that both the top and bottom
rolls act to give a positive feed. Immediately in front of the cutter
head and between it and the feed rolls (_i. e._ the front pair of
rolls), is a pressure bar extending across the full width of the
machine, and having at its lower extremity a steel spring which presses
the work down to the table, and thus causes it to be planed of an equal
thickness throughout its length. Immediately behind the cutter head and
between it and the delivery rolls (_i. e._ the back pair of rolls), is a
pressure bar that also extends across the machine and prevents the
timber from rising up from the table after it has passed the cutters,
all timber being found to have a tendency to rise after having been
acted upon by the cutters. The arrangement of the feed rolls, delivery
rolls and pressure bars is shown in Fig. 3158, in which T, T, T,
represents three sections of the work table and W, W, a piece of work
passing through the machine in the direction of the arrow. Feed roller F
is fluted to increase its grip upon the work and insure a positive feed.
The lower feed roller F´, and the lower delivery roller D´, are fixed in
position, their upper surface projecting above the work table to about
1/100 inch. This is necessary to take the thrust of the upper rolls (F,
D) and prevent them from forcing the work down upon the surface of the
table with an undue amount of pressure, which would induce friction and
consume an unnecessary amount of power in driving the rolls. The method
of adjusting the lower rolls will be explained presently.
Between the cutter head C and the feed roll F is the pressure bar P, and
behind the cutter head is the pressure bar B, both these bars being more
clearly seen in Fig. 3159, in which the work W is shown entering the
machine, and the lower rolls and work table are removed.
Pressure bar P has at its lower end a steel spring J, Fig. 3159, and is
supported at each end by circular links Y, projecting into grooves
provided in the main frame of the machine, as shown in Figs. 3160 and
3161, in which C is the cutter spindle, Y the circular link at the end
of pressure bar P, and _y_ the circular link at the end of pressure bar
B, the two fitting into the one stepped groove.
[Illustration: Fig. 3160.]
[Illustration: Fig. 3161.]
This groove is concentric with the cutter spindle C, so that the
pressure bars keep at a positive or equal distance from the edges of the
cutter, no matter what the thickness of the work or the depth of the cut
may be.
[Illustration: Fig. 3162.]
In Fig. 3162, the work is shown passing beneath the two upper rollers,
and the spring J (which extends the whole length of the pressure bar),
is depressed from the weight of the bar. By this construction, the work
is pressed to the table at a point as close as possible to the cutters.
The pressure bar P cannot drop beyond a certain point, because of its
tail piece _y´_, Fig. 3160, which rests on the top of the frame at _y´´_
when the bar P has fallen to its required limit.
The feed pressure bar P is bolted to its circular links, as shown in
Fig. 3162, in which Y is a part of the circular link which is bolted to
the pressure bar P.
The delivery pressure bar B (Fig. 3160) is riveted to and forms part of
its links _y_. It acts through the medium of spiral springs _s_, which
are carried in cases or boxes _s´_, which overhang the end of the bar B.
A set screw _s´´_ regulates the pressure of the spring, and a screw _a_
(Fig. 3162) regulates the height of the pressure bar.
The adjustments of the feed and delivery rollers are made as follows:
The feed pressure is obtained through the medium of weights, shown at W,
W´, in Fig. 3163, upon the bars A, A´, whose ends are pivoted to the
lower ends of links _m_, _n_, the upper ends of which are pivoted to the
side frame of the machine.
Bar A engages or rests at _e_, on a lug or projection on the link I,
which fits in a recess provided in the side of the frame. This link I,
extends up and has a bearing to receive the feed roller (F, Fig. 3160),
whose driving gear is shown at O.
It is obvious therefore, that the amount of pressure on the feed roller
F may be varied by moving the weight W along the bar A.
Similarly for the delivery pressure roller, the weight W´ is adjustable
along the bar A´, which is pivoted to link _n_, and rests upon I at
_e´_. The link I´ is guided in ways in the side frame of the machine,
and at its upper end carries the delivery roller D, whose driving gear
is shown at O´ (Fig. 3163).
It is obvious that there are bars A, A´, and links I, I´, on both sides
of the machine, so as to adjust the feed rollers at both ends.
The work table and the two lower rollers are adjusted for different
thicknesses of work as follows:
Between the two main side frames M and M´, Fig. 3164, are two frames
having corresponding inclines or slideways, of which the upper carries
the work table and the lower rolls.
[Illustration: Fig. 3163.]
The lower incline sits on ways K, K, Fig. 3164, cast on the side frame,
and is capable of being moved endwise by means of the hand wheel R,
Figs. 3163 and 3164, which operates a screw threaded into the lower
incline. When the lower incline is moved endways, the upper one, which
carries the work table, is moved vertically, and as the lower feed rolls
are carried by the upper incline, and the upper rolls are guided to move
vertically only, the lower rolls maintain their position beneath the
upper ones, or in other words, the table and lower rolls move together
in a vertical direction only, when the lower incline is operated.
The lower rollers run in bearings formed in the links Q, Q, Fig. 3160,
which are pivoted at their other ends to the upper incline. On the sides
of the incline are lugs through which pass adjustment screws _z_, which
by operating beneath the outer ends of the links Q, Q, adjust the
heights, bearings of the lower rollers so that the uppermost point on
the circumference stands about 1/100 inch above the level of the work
table surface.
The upper surface of the lower incline is shown by the dotted line _f_,
_f_, _f_, in Fig. 3163.
We may now consider the means employed to drive the rolls, first
remarking that the upper rolls F and D, are given a motion slightly
quicker than the lower ones, so as to cause them to clean themselves
(from particles of wood that might otherwise cling to them), by a sort
of rubbing action which is due to their velocity being greater than the
lower rolls and the work. This rubbing action is due to the fact that
the work has the slower motion of the lower rollers, resisting the
quicker motion of the upper ones, and as a result there is a certain
amount of slip between the upper rollers and the work.
Another and important feature, is that the upper delivery roller (D,
Fig. 3260), is placed from 1/4 to 1/2 inch nearer to the cutter head
than the bottom delivery roll, which assists in keeping the work down
upon the table.
The mechanism for driving the feed rolls is shown in Figs. 3163, 3164
and 3165, in which L, L are the pulleys which receive motion from a
countershaft, and drive the cutter head, being fast upon its shaft, as
is also the pulley S, which connects by belt and drives pulley T, on
whose shaft is the stepped pulley U, which connects by a crossed belt to
pulley V, which drives the feed gear through the medium of the pinion
_a_. The two steps on pulleys U and V, obviously give two rates of feed.
The pinions O and O´, both receive motion from the gear wheel E, this
part of the gearing consisting of gears _a_, _b_, _c_, _d_ and E, and as
both pinions receive motion from the same gear, their revolutions are
equal. The lower feed roll is driven by the pinion _p_, which gears with
and is driven by wheel _d_, whose face is broad enough to meet _p_,
which sits nearer to the frame than pinion O does, so that the teeth of
_p_ may escape those of O.
Now the velocities of all the wheels O, O´, E, _d_ and _p_, will be
equal at the pitch circles, because they constitute a simple train of
gearing. Thus if _d_ moves through a part of a revolution equal to the
pitch E, then O and O´ will move through the same distance, because the
wheels are in continuous gear. Now as _d_ drives _p_, therefore the
velocity of _p_ must at the pitch circle be the same as _d_, let the
numbers of teeth in the respective wheels be what it may, and it follows
that the velocities of O, E, _d_ and _p_ are at the pitch circles equal.
But by making the diameter of the upper roll greater than the pitch
circle of its gear O, and the diameter of the lower roll correspondingly
less than the diameter of the pitch circle of its pinion _p_, the
velocity of the circumference of the upper roll will be greater than
that of the lower roll, and the rubbing action before referred to with
reference to the upper roll will thus be induced.
[Illustration: Fig. 3164.]
Referring now to the lower delivery roll, its pinion _x_ receives motion
through gear _w_, which is also driven by gear E, which has a broad face
so as to gear with _x_, which is behind and below gear O´. In this case
the circumstances are the same, as will be seen from the following.
An inch of motion of the pitch circle of E will produce an inch of
motion at the pitch circles of O´ and of _w_ and _x_, hence the
velocities of the pitch circles will be equal, and if the diameters of
the upper and lower rolls are equal, or the same as the pitch circles,
the velocities of the circumferences of the respective rolls will be
equal, but by making the diameter of the upper delivery roll greater
than that of the pitch circle of its pinion, and that of the lower roll
less, a rubbing action is induced between the roll and the work, and
this rubbing action will keep the roll clear of any dust, etc., that
might otherwise cling to it.
The cutter head is formed triangular, as in Fig. 3166, carrying three
knives. The knives are set at an angle to the axis of the cutter bar or
cutter head. When the knives are at an angle, they take their cut
gradually, and the cutting action is more continuous, which diminishes
the vibration of the machine, and causes the finished surface to be
smoother. Furthermore, the knives take a shearing cut, and therefore cut
more easily and freely.
In some practice the knives are made spiral, but spiral knives are
difficult to bed properly to the cutter head, and also difficult to
grind. The cutter head is made of a solid mild centre steel forging, and
runs in phosphor bronze journals, in which it has about 1/8 inch end
play, which tends to distribute the oil along the bearing. It is driven
by a pulley at each end, the pulleys seating on a cone.
The amount of skew is about 3/4 inch for a cutter head carrying a knife
30 inches long, and about 3/8 inch for a cutter head whose knives are 10
or 12 inches long.
[Illustration: Fig. 3165.]
[Illustration: Fig. 3166.]
[Illustration: Fig. 3167.]
Figs. 3167 and 3168 represent a machine in which there are three feed
rolls and one delivery roll, all being driven.
First there is the pair of feed rolls the bottom roll of which is set
sufficiently above the surface of the table to relieve the work of
friction upon the table.
The work next meets an upper feed roll that acts to force the work down
to the table surface (there being in this case no lower feed roll).
After passing the knives, the work is carried out by a delivery roll
that also acts to keep the work down to the table face.
All three upper rolls are provided with rubber springs in the casings H,
H´.
P, P, are the pulleys for the cutter head and B, those for the feed
works, which have two speeds. The feed is thrown in and out by the lever
_d_, which moves the pinion D endways and engages or disengages it from
its gear wheel.
[Illustration: Fig. 3168.]
[Illustration: Fig. 3169.]
Figs. 3169, 3170, 3171 and 3172 represent a pony planer, by P. Pryibil.
[Illustration: Fig. 3170.]
Referring to the sectional view Fig. 3170, the work table slides in
vertical slideways S, in the side frames, the elevating screw being
operated by the bevel gears at G, which receive motion from the hand
wheel M in Figs. 3170 and 3171. There are four upper rolls, marked 1, 2,
3 and 4 respectively, and of these the first two are fluted in the usual
way. There are two lower rolls, marked respectively 5 and 6. The fluted
feed rolls 1 and 2 are weighted, the weight lever acting on the rod R,
which at its upper end connects to the cap Y, which covers the bearings
of feed rolls 1 and 2. By this construction the two rolls are acted upon
by the same weights and levers, the rolls being of course weighted at
each end, or in other words on both sides of the machine.
The delivery rolls 3 and 4 receive their pressure by the construction
shown in Fig. 3172, the bearings of the rolls being held down by rubber
cushions receiving pressure from the cap E, screwed down by the bolt and
nut.
The rolls 5 and 6 are idle rolls, and are set to just relieve the work
from undue pressure on the work table.
By this construction of feed mechanism the following ends are attained.
First, sufficient feed power for heavy cuts is obtained without driving
the lower rolls. Second the work is held to the table on both sides of
the cutter head, hence there will not be left on the end of the work the
step that is left when but two upper and two lower rolls are used, and
which occurs because the work falls after leaving the feed rolls,
whereas, in this machine the work is held to the table by rolls 2 and 3.
The cutter head H, Fig. 3170, has in front of it the pressure bar P,
whose lever is shown at L and the weight at W. On the delivery side of
the cutter head is a pressure bar _r_, which is acted upon by a spiral
spring in the box C. In the engraving to the right of Fig. 3170 the
knife K is shown in action on a piece of work, and it is seen that the
end of the pressure bar P coming close to the edge of the knife prevents
the pressure of the cut from splitting or splintering off the end of the
work at _a_, and therefore acts as what is termed a _chip break_.
Furthermore, the sides of the cutter head between the knives being
hollowed out gives the shavings _s_ room to curl in and prevent the work
from splintering at the end when the cut is terminating.
BALANCING CUTTER HEADS AND KNIVES.--Planer knives must be balanced as
accurately as possible, in order that they may run steadily and
smoothly, and therefore produce smooth work.
The first requisite for proper balancing is that the cutter head itself
be properly balanced, and in order that this may be the case the faces
forming the knife seats must be equidistant from the axis of the cutter
head, and the journals must run true, being best tested on dead centres.
The holes for the cutter bolts should all be drilled to the same depth,
and tapped equally deep. The faces or seats for the knives should be
parallel one to the other, and this may be tested by a pair of straight
edges, one pressed to each face and the width between them measured at
each end, or if a long surface plate is at hand, one face of the head
may be rested on the surface plate, and the straight edge ruled on the
other face, and its distance measured from the surface plate at each
end, with a pair of inside callipers delicately adjusted.
A straight edge rested lengthways along the knife seat of the head and
projecting over the journal will show whether each knife seat is
equidistant from the journal as it should be, the measurement being
taken with a pair of inside callipers adjusted to just sensibly touch
the journal and the straight edge. This measurement should be taken at
each end of the head.
In all tests made with straight edges, the straight edge should be
turned end for end and each measurement repeated, because, if the
straight edge is true, turning it end for end will make no difference to
the measurement, while if the straight edge is not true the measurement
will vary when the straight edge is reversed.
If the cutter head is square, the straight edge tests may be applied to
all four of its faces, and they may then be tested with a square, and if
the head shows no error under these tests, and the bolt holes or slots
are of equal diameter and depths, the head will be correct as far as it
can be tested without running it.
[Illustration: Fig. 3171.]
[Illustration: Fig. 3172.]
A cutter head may be roughly tested by placing it between the lathe
centres, both centres being oiled and delicately adjusted so as to just
prevent end motion of the head without perceptible friction when the
head is revolved by hand.
The first thing to test is whether the journals run true, which may be
tested by a pointer fastened in the slide seat, and moved up to just
touch the journal. The pointer should be soft, and not a cutting tool,
unless indeed it be set so high in the slide rest that it cannot cut.
If the journals do not run true, the next thing to test is whether the
body of the head runs true to the centres, which may be done by first
setting a pointer to just touch the extreme corners of the head at each
end and in the middle of its length, and if there is an error in the
same direction as the test at the journal shows, then the centres of the
head are out of true, and must be corrected before a test of this kind
can be proceeded with.
But the body of the head may show true at the corners while the journals
do not run true, and if this is the case we may further test the body of
the head as follows:
With the lathe slide rest at one end of the head we may set a pointer so
that it will just pass on the flat of the cutter seat and make a mark
when the slide rest is traversed along the lathe bed. We then move the
slide rest so as to bring the pointer to the journal end of the head;
give the head a half a revolution on the centres and try the pointer on
the flat of the cutter seat, and if it makes a mark of equal strength,
then two faces of the head are equidistant from the axis of the head.
The next thing to do is to make the same test at the other end of the
head, and in order to do this without moving the pointer, and therefore
without altering its adjustment, we must move the slide rest so as to
bring the pointer opposite to the lathe centre, and out of the way of
the body of the head, and take the cutter head out of the lathe and turn
it end for end, and then repeat the test with the pointer, which will
show whether both ends of those two flats are alike.
This test we repeat on the other two faces of the head, and if they show
true, then the head is true, except the journal, which must be made true
with the head.
This testing will clearly show any want of truth in either the head or
the journals, and in what direction correction needs to be made.
Now suppose the above tests do not disclose any error, either in the
journals or in the head, and we may continue the tests by revolving the
head by hand between the dead centres, and apply the pointer to the
journals while the head is revolved as quickly as possible; as, however,
the head cannot be revolved very fast in this way, we may adjust the
lathe centres as before described, and revolve the head as rapidly as
possible by hand, and letting it come to rest mark which side is at the
bottom, and if on several tests the same side comes to the bottom of the
plane of revolution at each test, that side is the heaviest and must be
corrected. If it is found to be a flat side or cutter seat that comes to
rest at the bottom, the correction can be made by deepening the bolt
holes on that side, measuring to see which bolt hole is the shallowest,
and making all as nearly as possible equally deep.
If the head has T slots instead of bolt holes, the slots may be cut or
filed out to effect the balance, care being taken to make the slot equal
in distance from the edges of the cutter seat face.
The next essential in order to have a properly balanced cutter head is
that the bolts and nuts all weigh alike, and that the bolts be of the
same length. The bolts should be turned to an equal diameter of equal
length and threaded for an equal distance along the body of the bolt,
and the nuts should be of equal depth and all fit accurately to the same
wrench, and the weight of the bolts and nuts when put together may then
be equalized by reducing the heads of the heavy ones.
We now come to the balancing of the knives, which must be made of equal
thickness and width throughout, with the slots for the bolts of equal
widths and depths.
The knives require to be as accurately balanced as it is possible to
make them, for otherwise they will cause the head to jar and vibrate
violently, thus producing rough work. The knives weighed individually
may be of the same weight, and yet the head may run out of balance by
reason of one end of a knife being heavier than the other end.
[Illustration: Fig. 3173.]
Fig. 3173 represents a machine constructed by J. A. Graham & Co., for
balancing planer knives, moulding knives, cap screws, and knives in
rotary cutter heads of all kinds.
Let it be supposed that the knives are the same specific weight, but
that there is an excess of weight at one end; when revolving on the
head, a violent jarring or throwing will be caused by reason of the
excess. The knives could be reduced to the same specific weight by the
aid of common grocers' scales, but the ends could not be made the same
proportional weight as on such balance.
In the cut S S is the base of the scale; L, M the standards for the
support of the scale beams B B and K K.
_d_, _d´_ are two pivots of the scale beams.
D is the loop on which the pivot _d_ works.
E is a joint in the loop.
D´, E´, and F show the loop and connection.
_c_ is the sliding table which has the stop _c´_, and is adjustable for
different lengths of knives.
_a_ _a_ is a knife in position for balancing endwise.
G is a slotted piece, and is held to the scale beam by the screw _v_.
The slot in G is shown at G´, and limits the travel of the scale beams.
H is an angular piece fastened to the lower scale beam, and receives the
screw J.
I is a small weight used for fine adjustment.
O, O are weights which slide along the scale beam K K, and are held in
place by the thumb screws P, P.
N shows side view of weight, which is so constructed as to allow it to
be easily removed. In using the machine the lightest cutter or knife of
the set is first found and its two ends balanced, by turning it end for
end on the scales, and reducing the weight of the heavier end. The other
knife or knives are then balanced without disturbing the adjustment of
the machine as made for the first knife.
ENDLESS BED OR "FARRAR" WOOD SURFACING MACHINE.
This class of machine has a bed composed of slats which are connected
together and driven by a chain.
Fig. 3174 represents an endless bed double surfacer constructed by the
Egan Company. The upper cylinder may be raised or lowered to suit the
thickness of the work. The front feed roll is in two sections, enabling
two boards of unequal thickness to be planed simultaneously to an equal
thickness. These rolls are held to the work by a leaf spring, as shown
in the cut, the tension on the spring being adjusted by the screw at D,
_d_ serving as a check-nut.
A longitudinal section through the centre of the machine is shown in
Fig. 3175. The spring S bears at each end on a block T, which carries
the bearings for the feed roll. Feed roll M is held down by the screws
E, E, acting on a rubber cushion or spring, and is provided with a
scraper to clean it from dirt, etc.
The travelling bed is composed of slats S connected together by the
chain shown, and resting upon slides A, A, supported by the girts B, B.
The chain is operated by the spur or sprocket wheel W, and is therefore
pulled and not pushed, which tends to keep it under tension, and
therefore rigid upon the top side.
The ends of the slide A, A are depressed so that the slats shall not
tilt up at one corner above the level of the slide when in the positions
denoted by S´.
The lower cutter head is carried in a sliding head or frame J, adjusted
for height by the gears at H, which operate screw _h_, while the bed
above it is adjusted by the gears at F. It is obvious that the bottom
surface of this bed is set at the same height as the lowest point in the
path of revolution of the cutting edges of the knives of the front
cutter head or cylinder. The upper delivery roll N is provided with a
scraper.
PLANING AND MATCHING MACHINE.
Planing and matching machines that are made narrow to suit the planing
and matching of boards for flooring are sometimes called _flooring_
machines, the distinctive feature of a flooring machine being that it is
(unless in the case of a double machine) made narrow (because flooring
boards are narrow), and this makes the machine very stiff and capable
therefore of a high rate of feed and speed.
[Illustration: Fig. 3174.]
[Illustration: Fig. 3175.]
[Illustration: Fig. 3176.]
[Illustration: Fig. 3177.]
Fig. 3176 is a general view, and 3177 a longitudinal section through a
standard planing and matching machine of recent design, constructed by
Messrs. J. S. Graham & Company. The plank passes through two pairs of
rollers before meeting the front cutter head. The side heads then come
into operation cutting (in the case of flooring) the tongue on one side
of the plank and the groove on the other, the under side of the plank
being dressed last.
The machine is built in three widths viz., 8", 14" and 26", each planing
to 6" thick and matching as wide as it planes.
In place of matching heads, heads for beading, rabbeting, or fancy
siding may then be used.
The board R (Fig. 3177) is fed in over the grate _m´_ until it reaches
the rolls E and F´, which are held in place by the boxes fitted to the
roll stand _n´_, and brought to bear on the lumber by means of the screw
_a´_, equalizing bar _m_ and nuts _p_, _p_, together with the lever Y Y
and the weight _x_.
[Illustration: Fig. 3178.]
After the lumber leaves the second pair of rolls, it runs over the bed
plate W (Fig. 3178) and under the shoe L, the duty of which is to hold
the board firmly against the bed plate, and also to break the chips on a
heavy cut. After leaving the shoe it is operated on by the upper cutter
head H, then it passes beneath the pressure bar _g_, which holds the
lumber firmly while it is acted on by the matcher _c_.
[Illustration: Fig. 3179.]
It then passes beneath the cleaner E´´ (Fig. 3177) and under the
delivering roll, which is held down by the weight U in connection with
the lever V and screw _a´_, the top which is shown at C (Fig. 3179). The
board then passes underneath the pressure bar Q (Figs. 3177, 3180) and
over the under cutter S, from which it passes finished.
The pressure bar Q is moved up and down by turning the shaft _a´´_, the
motion of which is given to the screw _h´_ by means of a pair of bevel
gears. _k´_ is also a scraper that cleans the board before it passes
under the pressure bar Q. The under cutter is adjusted for depth of cut
by turning hand wheel A´, which moves the screw U´. The rolls are raised
and lowered by turning the shaft at P (Fig. 3176).
In feeding two boards through the machine, one thicker than the other,
that end of the roll that passes over the thick board can raise up
without taking the pressure off the thin one at the other end of the
roll. This raising mechanism is shown in Fig. 3179. The bevel gear C
works over a ball joint Q´. The shoulder B´ on the screw _a´_ works on
the under side of the ball Q´. The shaft _a_ passes through the tubular
shell B to the opposite end of the roll. The cross tie J is bolted to
the roll box K´´.
C, Fig. 3178, shows matcher hanger in position. It is gibbed to the bed
plate Z by the gib _f_, which is so constructed as to be free from dirt.
The sliding gib _f_ is adjustable for wear. One matcher hanger is moved
by the screw _e_, the other by _e´_. The left hand matcher hanger is
moved by the shaft _l´_ (Fig. 3177), which passes along the side of the
machine until it reaches the shaft _e_, where its motion is imparted to
the screw by means of a pair of spiral gears. An index at the rear of
the machine enables the operator to set the matcher heads to any desired
width. The right hand matcher hanger, together with the guide, can be
moved across the machine by turning the screw _e´_ at the side of the
machine (Fig. 3176).
The upright D which carries the pulley which drives the top cutter head,
or cylinder as it is sometimes termed, is set at an angle so that the
cylinder belt will always be of the same tension.
The top cylinder is raised by the shaft _d_ (Fig. 3176) and screw _b_.
It is held in place by the nut M (Fig. 3177). The bar I ties the
cylinder boxes together. K is held down by the weight I, and yields with
the pressure bar L.
The spindle of the matcher _c´_ (Fig. 3177) is driven by a belt which
comes from the pulley _h_ and passes over the guide pulley _k_, and then
to the pulley _b´_.
The lower end of the matcher is held in place by being gibbed to the
cross tie _p´_, Fig. 3177, which is adjusted and kept in position by the
screw _o´_.
S´ sustains the matcher spindle by means of an adjustable step.
Y´, Fig. 3176, is the feed shaft which drives the gearing that operates
the rolls. The pulley that drives the feed shaft is shown at L´ (Fig.
3176). The belt passes over this pulley and under and over the tightener
pulleys _w´_, _w´_, then to the pulley U´ which is on the feed shaft Y´.
[Illustration: Fig. 3180.]
The apron M´ in front of the under cutter S (Fig. 3180) is easily
dropped to M´´ by loosening the nut R´ and releasing the bolt T´ so as
to allow the apron M´ to drop.
This enables the operator to have free access to the under cutter for
sharpening knives, etc. _z´_ is the bed plate over which the lumber
passes before it reaches the under cutter.
[Illustration: Fig. 3181.]
[Illustration: Fig. 3182.]
A planing and matching machine designed and constructed by Messrs.
London, Berry and Orton is represented in Fig. 3181. In this machine the
upper surface of the board is surfaced first, and the matching second,
the under surface being operated upon the last. The method of suspending
the upper feed rolls of this machine is shown in Fig. 3182, in which A
is an upper and B a lower feed roll. The upper roll A is suspended by
the link C, which is supported by the link D, and also by link E, these
three links forming a parallel motion which guides A in a vertical line.
At F (which is fast to E) is a bearing for the screw G, and the pair of
bevel gears _g_ that drives it. This screw threads into the nut H on the
rod I, which receives the pressure of the bar J and weight K.
The lower feed rolls being larger in diameter gives them increased grip
on the work, and gives it a better base, and also makes it enter and
leave the rolls easier.
Each matcher bracket is fitted with a screw by which it can be moved at
will across the machine, and by turning one other screw with the same
wrench that moves the others, both brackets are firmly set to the slide
and all screws held firmly. There are three changes of feed. The top
cutter head is provided with improved pressure bars, which are set to or
from the head by means of a double eccentric, which, while they can be
set at any desired distance from the knives, limits their movement when
moved towards them, rendering it impossible to get them into the
cutters.
TIMBER PLANER.
The term timber planer implies that plain knives only are used in the
machine, which is therefore intended for producing plane surfaces. It
also implies that the machine is designed for heavy or large work, such
as is found in ship yards, bridge construction or car works, etc., etc.
In such work the cuts taken by the machine are sometimes very heavy, and
as a result the feed works of the machine require to be very powerful
and positive.
Fig. 3183 represents a timber planer designed and constructed by J. S.
Graham & Co., to plane all four sides of the timber at one passage
through the machine.
The timber passes through three pairs of feed rolls before reaching the
first cutter head, which planes the bottom surface.
It then passes to the side heads, which dress both sides simultaneously,
and then passes beneath the cutter head that finishes the upper surface,
and is finally delivered from the machine by a pair of delivery rolls.
The work is passed over roller B, the fence or gauge being shown at B´.
1 and 2 are the first pair of feed rollers, _a_ and _b_ being merely
adjustable intermediate wheels, which by means of the pieces _c´_, _b´_,
may be set so as to connect rollers 1 and 2 together, whatever their
distance apart may be, or in other words whatever the thickness of the
work may be.
[Illustration: Fig. 3183.]
From 1 and 2 the work passes to the second pair of feed rolls 3 and 4,
_c_ and _d_ being the intermediates.
Similarly 5, 6, 7 and 8 are feed rolls, and _e_, _f_, _g_, _h_
intermediates. The first head is shown at K´, the side heads at H, and
the last head at I´, the latter being carried on a sliding head J, which
is secured in its adjusted position by nuts I. On the side of the frame
D on which J slides is a graduated index to denote the adjustment of the
head I´.
[Illustration: Fig. 3184.]
The construction of the parts in immediate connection with the front
cutter head is shown in Fig. 3184. N is the frame corresponding to N in
Fig. 3183, the rolls 5 and 6 also corresponding in the two figures.
Upon N is a slide S having an arm G, carrying the roll G´, which holds
the timber down to the cut of the cutter head K´. The pressure of roll
G´ to the work is given through the medium of the rod _a´_, which
receives the pressure of the equalizing bar _x_, Fig. 3183.
The bottom surface of the timber passes over the bed plate U, Fig. 3185,
which raises and lowers with the lower feed rolls, being connected by
the screw _i_, Fig. 3184, to the bearing box of feed roll 6.
All the lower feed rolls are operated simultaneously by means of the rod
_l_, having for each lower feed roll a worm, driving a worm wheel _l´_
on a screw threaded into a hub _m_ in each feed roll bearing; the crank
for operating _l_ is seen at P, Fig. 3183.
[Illustration: Fig. 3185.]
The passage of the timber through the machine is continued in Fig. 3185,
in which it is seen that after the lower surface of the timber has been
planed it passes from the cutter head K´ to a bed plate V and is thus
supported by a flat and true surface while the side cutter heads plane
the two sides, one of these side heads being shown at H. The side heads
are carried in hangers, one of which is shown at _p´_. It is gibbed to
the under cutter frame U´ by the sliding gib _x_, the left hand head H
being moved across the frame by the screw _f´_. The hanger is held at
the bottom by the gib _t_ and the cross tie _t´_. _p_ is the pulley for
the side head H, the end wear of whose shaft is taken up by the
adjusting screw _s´_, _r´_ being a leather washer, and _r_ the end of
the shaft.
[Illustration: Fig. 3186.]
The top box H´ moves across the machine in the slideway _b´´_, Figs.
3186, _a´´_ being a part of the box H´.
Upon leaving the side heads the timber will have been planed on three
sides and the side surfaces dressed to a right angle with the bottom
surface.
It is then guided to the upper cylinder as follows:
The friction rolls K, K are to relieve the bed A´´ from the pressure due
to the feed roll Z´ and the roll J´, which holds the timber after it has
left the cutter I´, and thus prevents it from vibrating. After leaving
the pressure roll J´, the timber passes under the scraper _d´_, Fig.
3183, and thence to the delivery roll 7, which is held down by the
weight L, in connection with the lever L´.
By means of this construction all the cutter heads act upon the timber
within the short distance of 22-1/2 inches, while the side heads act
within 8-1/2 inches of the under cutter. This is desirable, being
conducive to the production of true work, which it is more difficult to
produce in proportion as the cutter heads are wider apart. This machine
will joint as narrow as 2 inches, and plane as thin as 3/4 inch.
The upper cylinder I´, Fig. 3183, is adjusted for height or thickness of
cut by means of the screw _f_, and is locked in its adjusted position on
D by the nut I.
The feed is started or stopped by operating the hand wheel _o´_.
The upper rolls are raised or lowered simultaneously by power, by means
of the shaft _s_, and the bevel gears _r_, which operate the screw _a´_.
The upper cylinder is driven by belt from the pulley Q, the under
cylinder from Q´ (both these cylinders being driven from both ends). P´
is the driving pulley for the feed belt, which passes to N´, which,
through K´´ and Y´, drives Y, which drives the feed rolls.
The machine will feed from 25 to 60 feet per minute.
PANEL PLANING AND TRYING-UP MACHINE.
This class of machine is employed for the production of true surfaces,
and is now used upon much of the work that was formerly assigned to the
Daniels class of planing machine. In this machine, as in the case of the
Daniels planing machine, the work is secured to the table, which travels
to carry the work to the feed.
Fig. 3187 represents a machine by J. Richards, in which a cutter head
with skew cutters is employed, and a pressure roll is placed in front
and at the back of the cutter head, the construction being as follows:
Upon the main frame are the slideways _t_, _t´_, upon which the
cross-head or cutter head frame Z is carried, the elevating screw S
raising or lowering the frame Z, to suit the thickness of the work. The
cutter head C, whose driving pulleys are shown at P, P, is carried in
frame Z, which also carries the pressure roll in front of the cutter
(the bearing for this roll being shown at R), and a similar roll behind
the cutter. To the frame Z are pivoted the pressure bars B, B´, weighted
with weights W. These bars rest on the cross-heads Y, whose pins _p_ act
on the bearing boxes of the pressure rolls.
The cutter head frame may be raised or lowered, for varying thicknesses
of work, either by hand or by power. The hand movement is obtained from
the hand wheel W, Fig. 3188, which operates bevel gears _b´´_ and _b´_,
the latter being threaded to receive the elevating screw.
[Illustration: _VOL. II._ =TRYING-UP MACHINE.= _PLATE XXVI._
Fig. 3187.]
The power or belt motion for raising or lowering the cutter head frame
is obtained from rope wheel _w´_, which receives motion from the guide
pulleys shown in Fig. 3187. The wheel _w´_ drives its shaft by the
friction cone of its bore, which is forced against the corresponding
cone on the shaft by the hand nut L. The handle _v_, Fig. 3187, is for
operating the upper guide pulley _q_, which acts as a belt-tightening
pulley as well as a guide pulley, and the hand wheel _t_ holds _v_ in
its adjusted position. When _v_ is pushed downwards the rope (E) is
loosened upon the pulleys, and both rope and pulleys remain idle.
[Illustration: Fig. 3188.]
The pulley that drives rope E is shown in Fig. 3189 at R.
The feed motions for the work table are shown in Fig. 3189, and the
construction is such that for ordinary work the table has a quick return
motion, while for heavy work the feed and return motions of the table
are speeded alike.
The driving pulley B, Fig. 3189, for operating the feed mechanism,
receives motion by belt connection from the countershaft, and drives the
shaft on which are the bevel gears _b_ and _d_, and from these gears the
feed motion and quick return are derived, while from gear _e_ and pulley
R the cutter head may be raised and lowered by belt power as occasion
may require. Beginning with the feed motion, the gear _d_ drives gears
_e_ and _f_, which are a working fit on the shaft S. Between these two
gears is the clutch _r_, _r_, which is operated by the handle shown in
the perspective view, Fig. 3187, at _v_.
To operate the feed, clutch _r_ is operated to engage gear _e_ with the
shaft S, upon which is the friction wheel _m_, which engages with the
internal surface of the wheel or drum _g_, which drives the rope wheel
A, which drives the rope for the work table traverse--wheel A and the
rope being seen in the perspective view, Fig. 3187. The shaft N has
bearing in a piece that is virtually a sleeve eccentric, because its
bore is eccentric to its circumference; to this sleeve is attached a lug
_h´_ to which the handle _h_, Fig. 3187, is bolted. Now suppose that
handle _h_ is depressed, and then G will partly revolve wheel _g_ and
cause it to engage with the friction wheel _m_, which will drive _g_,
and therefore A.
Diametrally opposite to _m_ is a friction wheel _n_, which is driven by
the bevel gear _c_, and which is brought into or out of action with _g_
by the eccentric action of sleeve G, it being obvious that when the
sleeve G moves _g_ in the direction of _n_, _m_ is engaged and _n_
disengaged from contact with _g_. Raising the handle _h_ therefore
places _n_ in gear with _g_, which revolves it in the direction
necessary to draw the work table on the back or return stroke.
The return motion of the table is more rapid than the feed motion
because gear _c_ is of smaller diameter than _b_, and _n_ is larger than
_c_ and than _m_.
In the case of heavy work, however, the return motion may be made to
have the same speed as the feed motion by simply moving the clutch _r_
so as to engage wheel _f_ with the shaft S.
The rope groove in the pulley A is waved as denoted by the dotted lines,
and this prevents the rope from slipping, notwithstanding that the rope
envelops but half the circumference of A. The wire rope from A operates
a drum, in which are waved grooves for the table traversing rope which
winds around this drum, and attaches to pins (K, Fig. 3187) carried in
brackets at the ends of the table, and one of which is shown in Fig.
3187, at _z_.
The slack of the rope is readily taken up (as occasion may require) as
follows:
[Illustration: Fig. 3189.]
The pin _k_, to which the rope is fastened, has at one end a squared
head to receive a wrench to revolve the pin and wind up the rope, set
screw _l_ locking the pin after the rope tension is adjusted.
We have now to explain the method of holding the work, which is as
follows:
The side frames forming the bed are bolted to the main frame and form
the ways on which the work table travels. The table frame J, Fig. 3187,
is provided with rollers, which rest on the upper surface of the bed and
reduce the friction.
The table is made in convenient sections bolted to the table frame J,
and at their points of junction the work-holding dogs are placed, the
construction being shown in Fig. 3190, in which T´ is the end of one,
and T´´ the end of another section of the table. Referring now to Figs.
3187 and 3190, upon the edge of the table are the abutment pieces _a´_,
_a´´_, against which the work is pulled by the dog, which is operated by
the screw, which is squared at its outer end to receive the handle M,
Fig. 3187.
The rate of work feed is 30 feet per minute and the quick return motion
is 60 feet per minute.
MOULDING MACHINES.
In moulding machines for light work the feed rolls and cutter head
overhang the frame, such machines being designated as outside moulding
machines.
Fig. 3191 represents a machine of this class constructed by J. A. Fay &
Company.
The table T slides on vertical ways on the main frame, being adjusted
for height by the hand wheel W.
The work while fed over table T is pressed against the vertical face A
by the four springs shown, whose pins swing to suit the width of the
work.
[Illustration: Fig. 3190.]
[Illustration: Fig. 3191.]
The two feed rolls are made up in sections or discs and the pressure bar
is pivoted and has the weight shown to adjust its pressure to suit the
work, and is combined with the bonnet whose shape throws the shavings
outwards from the side of the machine. The particular machine here shown
is constructed substantially enough to permit of its being used for
light planing or work not exceeding 6 inches in width, a head with
planing knives being shown in place on the machine. In a machine of this
kind it is essential that the cutter head spindle and its bearings be
rigid, and with ample journal bearings and free lubrication to prevent
wear, and for these reasons the arbor is of steel running in self-oiling
bearings of large diameter. The arbor frame is capable of lateral
movement to enable an accurate adjustment of the cutters to the work.
The term _sticker_, as applied to a machine of this class, means that it
is suitable for light work such as window sash and door stiles, blind
slats, etc., etc.
Fig. 3192 represents a machine termed by its manufactures (the Egan
Company) a "double head panel raiser and double sticker combined." The
term panel raiser means that the edges of the work may be dressed down
so as to leave a raised panel. To fit the machine for such work the bed
or table T is made wide.
The upper feed rolls are in sections, and the lower one extends nearly
across the bed. The upper feed rolls are held down by a spring, whose
tension may be regulated by a hand wheel with an adjustment at the back
end to give a lead to both rolls. By this is meant that the plane of
revolution of the feed rolls inclines toward the cutter head so that as
the rolls feed they exert a pressure on the work, holding it securely
against the face A.
A long spring extends from the front of the feed rolls past the back or
bottom cutter head, passing as shown beneath the pressure bar, and is
adjustable for height from the bed or table face T by having its ends
pass through two studs in which they may be secured by set screws. This
serves to keep the work down to the surface of T.
The cutter heads for panelling have three cutters set askew or at an
angle to their plane of revolution so as to give a more continuous and a
shearing cut, which is conducive to smooth work.
The bed above the lower cylinder is adjustable for height by means of
the screw at H.
MOULDING CUTTERS.
[Illustration: Fig. 3192.]
In the ordinary or common form of moulding cutter, the front face is
flat and the lower end is bevelled off and filed to shape so as to give
the required shape and keenness to the cutting edges, Fig. 3193 giving
examples of such cutters.
[Illustration: Fig. 3193.]
Cutters of this class must be sharpened by filing the bevelled edge,
which requires considerable skill in order to preserve the exact shape
of the moulding.
SOLID MILLED CUTTERS.
[Illustration: Fig. 3194.]
[Illustration: Fig. 3195.]
In the solid milled cutter the bevelled surface at the cutting end of
the cutter is a plane, and a curved, stepped or other shape is given to
the cutting edge by cutting or milling suitably shaped recesses on the
front face of the cutter as shown in Figs. 3194 and 3195, the former
being a tongue cutter for cutting a groove, and the latter a grooved
cutter for cutting a tongue.
[Illustration: Fig. 3196.]
[Illustration: Fig. 3197.]
Other examples for such cutters are given as follows:
Fig. 3196 represents a cove cutter and Fig. 3197 an ogee. Fig. 3198, a
double beading, and Fig. 3199 a bevel cutter, and it is obvious that by
a suitable arrangement and shape of groove cutting edges of any of the
ordinary forms may be produced.
[Illustration: Fig. 3198.]
[Illustration: Fig. 3199.]
The advantages of such cutters are that the plain bevelled face or facet
of the cutter may be ground (to sharpen the cutter) on an ordinary emery
wheel or grindstone, and the shape of the cutting edge will remain
unaltered, providing that the cutter is always held to the grinding
wheel or stone at the same angle, so that the length of the bevel
remains the same.
A common practice is when making the cutter to so regulate the depth of
the grooves or recesses in its face that the cutting edge will be of the
required shape when the length of the bevelled facet is equal to three
times the thickness of the cutter.
The method of finding the shape of cutter necessary to produce a given
shape of moulding has been fully explained on pages 80 to 85, Vol. II.
[Illustration: Fig. 3200.]
[Illustration: Fig. 3201.]
Various forms of side heads are shown in the figures from 3200, to 3207.
Fig. 3200 is a two-sided plain head, or in other words two diametrally
opposite sides of the head are provided with bolt holes, for cutter
fastening bolts. Fig. 3201 represents a four-sided slotted head, each
side having T grooves, so that the cutter may be adjusted endways on the
head. This enables the use of four narrow cutters, thus taking the cut
in detail as it were.
[Illustration: Fig. 3202.]
[Illustration: Fig. 3203.]
The two-sided head shown in Fig. 3202 is provided with a set screw, by
means of which a delicate adjustment of the height of the cutter may be
made. Fig. 3203 represents a three-sided slotted head, or in other words
T-shaped grooves, and not bolt holes are used.
CUTTER HEADS WITH CIRCULAR CUTTERS.
[Illustration: Fig. 3204.]
This form of cutter head was invented by S. J. Shimer, and are generally
known as Shimer cutter heads. The principle of construction is shown in
Fig. 3204, which is for an ogee door pattern.
The cutters are circular in form and are seated at an angle to the
flange to which they are bolted, this angle giving side clearance to the
cutting edges.
[Illustration: Fig. 3205.]
[Illustration: Fig. 3206.]
The full amount of cut is taken in successive stages or increments; thus
in the figure, the two upper cutters would produce one half the
moulding, and the two lower ones the lower half. As the cutters are
sharpened by grinding the front face, therefore they will maintain
correct shape until they are worn out. Fig. 3205 represents a Shimer
head for producing the tongue, and Fig. 3206 a similar head for
producing the groove of matched boards.
[Illustration: Fig. 3207.]
Fig. 3207 shows the action of the groove head, the cutter or bit D being
shown in full lines and the second cutter being shown in dotted lines.
Cutter D, it will be seen, operates on one half of the groove, and
cutter C on the other half, each cutter having side clearance, because
of being seated on a seat whose plane is not at a right angle to the
axis of revolution of the head.
By thus taking the cut in detail, the head works steadily, while the
side clearance makes the cutters cut clean and clear.
JOINTING MACHINE.
"Jointing" a piece of wood or timber, means producing a surface, so that
the joint between two pieces that are to come together or be glued shall
be close. In order to produce surfaces that shall be true enough for
this purpose, it is necessary that the work be held in such a way that
it is not sprung or deflected by the holding devices or feeding
apparatus.
[Illustration: Fig. 3208.]
Fig. 3208, for example, represents a jointing machine, in which the work
abuts against an inclined plate P at one end, while the other end is
clamped down to the table, which is traversed past the revolving head H,
to which are secured two gouge-shaped cutting tools, one of which is
seen at T. By using tools of this class, the amount of cutting edge in
action is small, and will not therefore spring the work, and if the
cutter spindle is adjusted to have no end motion, the work will be true,
notwithstanding any slight vibration of the head, because its plane of
revolution coincides with the plane of the surface being surfaced or
jointed.
[Illustration: Fig. 3209.]
In some jointing machines, knives are set on the face of a revolving
disc, an example of this class of machine being shown in Fig. 3209,
which is for facing the spokes of wheels and for finishing the mitre
joint on them.
Three cutters are used, each being set at an angle to a radial line, so
that the inner edge of the knife will meet the work first. This gives
the knives a shearing cut, and prevents the whole of the cutting edge
from striking the work at once. The spokes are placed against a stop on
the table, and brought into contact with the cutters by the foot
treadle.
The table has beneath it a spiral spring at each end, which returns the
table as soon as the foot pressure is released from the treadle. The
cutter head or disc is 10 inches in diameter, and should make 2,000
revolutions per minute.
Stroke jointers are machines (such as shown in Fig. 3210) in which a
long plane _e_ of the ordinary hand plane type is worked along a slide
by a connecting rod C, operated by a crank motion. A machine of this
class will do very accurate work, but is obviously suitable for thin
work only.
A machine constructed by J. J. Spilker, for cutting mitre joints by
hand, is shown in Fig. 3211. The frame A carries a slideway for the
slide to which the mitre cutting knife K is secured. The handle G
operates a pinion gearing into a rack, which gives vertical motion to
the slide and knife. At _c_ is a fence or gauge against which the work
is rested, and which is capable of a horizontal motion, so as to bring
the work more or less under the knife. For heavy work, the fence _c_ is
set back, so that the first cut of the knife will leave the moulding, as
shown at H, partly severed, and a second cut is necessary to sever it;
for very fine work, a fine shaving may be taken off by a cut taken on
the end of each piece separately, after the piece is severed. At D is a
graduated scale or rule for cutting the work to exact dimensions, and as
its lines are ruled parallel to the right hand edge of the knife K, the
inside measurements of a mitre joint may be taken at the outer edge, and
outside measurements at the inner end of each line, a set stop at E
serving to gauge the pieces for length.
[Illustration: Fig. 3210.]
[Illustration: Fig. 3211.]
MOULDING OR FRIEZING MACHINES.
These are machines that cut mouldings on the edges of the work. The term
friezing is applied by some, when the machine has but one cutter
spindle, while by others these machines, whether having one or two
spindles, are termed edge moulding machines. Still another term applied
to this class of machine is that of variety moulders or variety moulding
machines.
In machines of this class, it is of primary importance that lost motion
or play in the bearings be avoided, because the cutter end of the
spindle overhangs its bearings, and any side play of the spindle in its
bearings is multiplied at the cutting edges of the cutters. Perfect
lubrication of the spindle bearings, and ample bearing surface on the
journals and bearings, are therefore of the first importance.
The work is rested on the upper surface of the table, and is fed to the
cutters by hand.
[Illustration: Fig. 3212.]
[Illustration: Fig. 3213.]
[Illustration: Fig. 3214.]
[Illustration: Fig. 3215.]
[Illustration: Fig. 3216.]
Figs. 3212 to 3215 represent a machine by J. S. Graham. The frame B, B,
Fig. 3213, of this machine is cast in one piece cored out, and the base
is wide, so as to give necessary solidity. The hollow column is fitted
with a door W, and shelves V, V, forming a very complete case for the
reception of tools, cutters, etc. The spindle boxes and slides C are one
casting. They are planed on centres and held in the frame B´, Fig. 3215,
by large gibs L, and sliding surfaces shown in C´, Fig. 3214. They are
adjustable vertically by hand wheels K, in front of frame in connection
with nut O, as shown in Fig. 3214, and require no lock to hold them at
the proper height.
The cap O´ (Fig. 3213) has an oil chamber J and wick which feeds the oil
to the upper bearing. The lower box is fitted with a patent self-oiling
and adjustable step shown at _a_, _b_, _c_. The cap _a_, upon which the
spindle D rests, has a small opening in the centre. The circular block
_b_, under it, also has a hole in the centre. The bolt _d_ has two holes
in it, one horizontal and the other vertical.
The chamber surrounding this step and cup is filled with oil. The motion
of the spindle D on the cap _a_ causes the oil to flow from the chamber
through the openings to the spindle. Thus the oil is kept in constant
circulation. The end of this spindle D is by this arrangement kept
always lubricated.
The spindles D are of 1-7/8 hammered tool steel accurately turned and
fitted in the boxes, which are of extra length, and lined with the best
genuine Babbitt metal. They are 30" from centre to centre, and have
independent screw tops, as shown at S, enabling the operator to use
various sizes for large or small work, or clear the table of either
spindle for special work.
H is the threaded part of the screw top, G is the nut, and F the fill-up
collars.
The iron table A, A is 5 feet by 4 feet, planed and fitted with
concentric rings E, E around the spindle, to suit the various sizes of
heads and cutters. A heavy wooden table, made of narrow glued-up strips
of hard wood, can be used if preferred.
This machine has been run up to 6,000 revolutions per minute, without
perceptible jar, and cutter heads as large as 8" diameter may be used on
it for heavy work.
Fig. 3216 represents an edge moulding machine by J. H. Blaisdell. In
this machine the table is raised or lowered by the hand wheel upon the
central column. The construction of the spindle and its bearings is
shown in the sectional view, which also shows the square threaded screw
by means of which the table is raised. The spindle has a coned hole for
receiving the cutter sockets, which are therefore readily removable.
[Illustration: Fig. 3217.]
Figs. 3217 to 3220 represent examples of the shapes of cutters for use
on edge moulding or friezing machines. Fig. 3217 represents a cutter for
bevelling the edge of the work, the cutting edges being at A, B, or at
C, D, according to the direction in which the cutter is revolved.
[Illustration: Fig. 3218.]
Fig. 3218 represents an ogee cutter, in position on the cutter spindle.
As these cutters are made solid and accurately turned in the lathe, they
are balanced so long as the cutting edges are kept diametrally opposite.
The front faces only being ground to sharpen the cutting edges, the
cutter always produces work of the same shape.
[Illustration: Fig. 3219.]
[Illustration: Fig. 3220.]
Fig. 3219 represents a cutter (in a chuck) for cutting a dove-tailed
groove, and Fig. 3220 one for rounding an edge, it being obvious that a
wide range of shapes may be given to such cutters, and that, as they may
be sharpened on an emery wheel, they may be left comparatively hard,
thus enhancing their durability.
To regulate the depth to which a cutter such as shown in Fig. 3220 will
cut, a collar or washer is placed beneath it to act as a guide to the
edge of the work.
[Illustration: Fig. 3221.]
Fig. 3221 represents a machine in which rotary cutters are used to
produce all kinds of panel work, as well as edge moulding or friezing.
In this case the cutter is above the table, the latter being adjustable
for height to suit the thickness of the work. Examples of some of the
work are shown at the foot of the machine.
WOOD BORING MACHINES.
The rapidity with which holes may be bored in wood enables the feed to
be most expeditiously performed by hand or by foot motion. A foot motion
leaves both the workman's hands free to adjust and change the work, and
is therefore suitable for light work or work having holes of a moderate
depth.
The work tables of wood boring machines are provided with suitable
fences for adjusting the work in position, and in some cases with stops
to adjust the depth of hole.
Any of the augers or bits that are used in boring by hand may be used in
a boring machine, but it is obvious that, as the bit or auger is forced
to its feed by hand or foot, and as its revolution is very rapid, the
screw point, which is intended as an aid in feeding when the bit is used
by hand, is not necessary. On this account most augers for use in
machines are provided with triangular points instead of screw points.
[Illustration: Fig. 3222.]
In Fig. 3222 is shown a wood boring machine by J. A. Fay & Co. The table
is gibbed to a vertical slide on the face of the column, and is
adjustable for height by the hand wheel A, which, through the medium of
its shaft and a pair of bevel gears, operates the elevating screw B. The
spindle C feeds through its bearings, the supporting rod D being pivoted
at its lower end to permit C to feed in a straight line vertically. The
feeding is done by the treadle F, which operates the rod E.
The table may be set at an angle of 30 degrees from the horizontal
position.
The weight W counterbalances the treadle and brings it to its highest
position when the workman's foot pressure is removed.
The holes may all be gauged to an equal depth (when they are not to pass
through the work) by so adjusting the height of the table that the hole
is of the required depth when the treadle is depressed to its lowest
point, or limit.
[Illustration: Fig. 3223.]
Fig. 3223 represents a horizontal boring machine such as used in
furniture and piano factories. The spindle feeds through the driving
cone, being operated by the treadle shown. The work table is adjustable
for height by the hand wheel and elevating screw. The usual fences,
stops, and clamping devices may be applied to the table, which is on
compound slides to facilitate the adjustment of the work.
Fig. 3223_a_ shows a double spindle horizontal boring machine, in which
the table and work are fed up to the boring tools by hand. The spindles
are adjustable in their widths apart, and may also be set at an angle.
The work table is adjustable for height, and the spindle carrying head
is adjustable across the machine.
[Illustration: Fig. 3223_a_.]
[Illustration: Fig. 3224.]
Fig. 3224 represents a machine by J. A. Fay & Co., for heavy work,
rollers taking the place of the work table. The drill spindles are fed
by hand from the stirrup handles shown, which are weighted to raise up
the spindles as soon as they are released.
MORTISING MACHINES.
The mortising machine for wood work consists essentially of an ordinary
auger, which bores the holes, and a chisel for cutting the corners so as
to produce the square or rectangular mortise that is usually employed in
wood work.
The chisel is reciprocated and its driving spindle is provided with
means whereby the chisel may be reversed so as to cut on either the
sides or the ends of the mortise. The chisel is fed gradually to its
cut.
[Illustration: Fig. 3225.]
Fig. 3225 represents a mortising machine for the hubs of wheels.
The auger spindle is here fed vertically by a hand lever, the depth
bored being regulated by a rod against which the hand lever comes when
the hole is bored to the required depth.
Fig. 3226 represents a mortising machine in which the mortising tool
consists of a hollow square chisel containing an auger, and having at
its sides openings through which the cuttings escape.
The chisel is rectangular in cross section, but its cutting edges are
highest at the corners, as may be clearly seen in the figure.
The work is firmly clamped to the work table and simultaneously to the
fence, the upper hand wheel being operated to bring the work-holding
clamp down to the work, and the lower one to clamp it so as to press it
to both the table and the fence at the same time.
The chisel bar is mounted horizontally in a slide way on a substantial
bed that is mounted on a vertical slideway, which enables the chisel bar
to be set for height from the work table. It has a horizontal traverse
motion or feed, the amount of this motion being governed by the
horizontal rod with its nuts and check nuts as shown.
The auger runs continuously, and works slightly in advance of the
cutting edge of the chisel, which is passive except when making the
mortise.
The chisel bar and auger have a slow, reciprocating motion, and will
complete a hole the size of the chisel used. An inch chisel will cut an
inch-square hole, consequently a mortise 1" × 4" would only require four
strokes forward to complete it. It has a capacity to work mortises from
3/4" to 3" square, and 5" in depth, and any length desired. The boring
spindle is driven by an idler pulley, direct from the countershaft.
The bed upon which the timber is placed to be mortised is gibbed to a
sliding frame, which allows it to be set to any position, with the
chisel straight or at an angle. It is adjustable to and from the chisel
bar, to suit the size of material, the under side of which always
remains at one height. Adjustments are provided for moving the carriage
forward, for regulating the depth of the mortise, the position of the
chisel from the face of the material, and the adjustment of the chisel
bar, controlling the mortises to be made in the timber.
Two treadles are used upon the side of the machine; the pressure upon
one carrying the chisel bar attachment forward, completing the mortise,
while the other will instantly force it back when it is desired to
withdraw it from the wood, without allowing it to cut its full depth.
Provision is made by stops for regulating the length of the stroke as
well as the depth of the mortise.
TENONING MACHINES.
In tenoning machines, the lengths of the pieces usually operated upon
render it necessary that the work should lie horizontally upon the
table, while the shortness of the tenon makes an automatic feed
unnecessary.
The revolving heads carrying the cutters in tenoning machines are so
constructed that the cutting edges of the cutters are askew to the sides
of the heads, but so set as to produce work parallel to the axis of the
cutter shaft.
This causes the cutting action to begin at one end of the cutter edge,
and pass along it to the other, which enables a steady hand feed, and
reduces the amount of power required to feed the work.
Fig. 3227 represents a cutter head for a tenoning machine, _a_, _a_ and
_b_, _b_ being the cutters and _c_, _c_, _d_, _d_ spurs which stand a
little farther out than the cutter edges, so as to sever the fibre of
the wood in advance of the cutter edges coming into action, and thus
preserve a sharp shoulder to the tenon, and prevent the splitting out at
the shoulder that would otherwise occur.
To bring the outer edge of the shoulder in very close contact with the
mortised timber, the cutters are for some work followed by what is
termed a cope head, which is a head carrying two cutters bent forward as
in Fig. 3228, to make them cut very keenly, as is necessary in cutting
the end grain of wood.
The cope head undercuts the shoulder, as shown at _a_, _a_, in Fig.
3229, which is a sectional view of a mortise and tenon.
[Illustration: Fig. 3226.]
[Illustration: Fig. 3227.]
[Illustration: Fig. 3228.]
[Illustration: Fig. 3229.]
[Illustration: Fig. 3230.]
Fig. 3230 represents a tenoning machine for heavy work, constructed by
J. A. Fay & Co., adjusted for cutting a double tenon, the upper and
lower heads revolving in a vertical plane, and the middle head in a
horizontal plane.
A is a vertical slideway for the heads C, D, carrying the shafts for the
cutter heads _a_, _b_. At B is the hand wheel for adjusting D, and at E
that for adjusting C. The pulley _d_ is for driving the cope heads, one
of whose cutters is seen at _c_. The work carriage H is provided with
rollers which run on the slide on K, and is supported by the arm I,
which rises and falls to suit the cross motion of H. The fence G, for
the work, is adjustable by means of the thumb nuts.
[Illustration: Fig. 3231.]
SAND-PAPERING MACHINES.
Sand-papering machines are of comparatively recent introduction in wood
working establishments, but are found very efficient in finishing
surfaces that were formerly finished by hand labor.
Fig. 3231 represents a sand-papering machine, by P. Pryibil, in which a
spindle has three stepped cones on one end, and a parallel roller or
cylinder at the other. The steps on the spindle are covered with a
rubber sleeve, and the sand paper is cut to a template, and the edges
brought together and joined by gluing a strip of tough paper under them.
When this has become dry the paper is slightly dampened everywhere
except at the joint, and is then slipped on the taper drums. In drying
it shrinks and becomes tight and smooth upon the rubber covering with
which the drums are provided. These are of different sizes to fit
different curves in the work.
Flat work is done upon the table, which is hinged and provided with an
adjusting screw to regulate its height, and it can be raised to give
access to the drum.
When sand paper is applied in this way, every grain is brought into
contact with the work, whereas at first only the larger grains cut when
it is used on the faces of revolving discs, as in some machines of this
class. Furthermore, when used on drums it is offered ample opportunity
to clear itself of dust; it therefore does not become clogged, and, as a
consequence, it lasts longer and does more and better work than when
used on discs.
[Illustration: Fig. 3232.]
Fig. 3232 represents a similar machine, but having a spindle vertical
also, so that one face of the work can be laid on the table, which acts
as a guide to keep the work square, the table surface being at a right
angle to the vertical spindle.
The vertical cylinder or drum is split on one side, and provided with
internal cones, so, that by screwing down the nut shown the drum can be
expanded to tightly grip the sand paper, which is glued and put on as
already described.
Besides these rotary motions, these drums receive a slow vertical
motion, the amount of which is variable at the operator's pleasure. This
provides for using the full face of the drum on narrow work, while it
prevents the formation of ridges or grooves in the work.
For sand-papering true flat surfaces the flat table is provided, there
being beneath it a parallel revolving drum, whose perimeter just
protrudes through the upper surface of the table. The surface of the
table thus serves as a guide to steady the work while the sand-papering
is proceeding.
By using sand paper in this manner, every grain of the sand is brought
into contact with the work; furthermore, a small area of sand paper is
brought into contact with the work, and the wood fibre can fly off and
not lodge in the sand paper; while at the same time the angles of the
grains of sand or glass are presented more acutely to the work, and
therefore cut more freely and easily. Hence the sand paper lasts much
longer, because a given pressure is less liable to detach the sand from
the paper.
The machine is constructed entirely of iron, and the drum is intended to
revolve at about 800 revolutions per minute.
[Illustration: Fig. 3233.]
Fig. 3233 represents a sand-papering machine in which a long parallel
cylinder is employed, the work resting on the surface of the table and
being fed by hand. In using a machine of this class the work should be
distributed as evenly as possible along all parts of cylinder, or one
end of the cylinder may become worn out while the other is yet sharp;
this would incapacitate the machine for wide work unless a new covering
of sand paper were applied.
Fig. 3234 represents a sand-papering machine constructed by J. A. Fay &
Co., for finishing doors and similar work. The frame constitutes a
universal joint enabling the sand paper disc to be moved anywhere about
the door by hand. An exhaust fan on the top of the main column removes
the dust from the work surface. The head carrying the disc is moved
vertically in a slideway to suit different thicknesses of work.
Fig. 3235 represents a self-feeding sand-papering machine constructed by
J. A. Fay & Co. It is made in three sizes, to work material either 24",
30", or 36" wide by 4" thick and under; it has a powerful and continuous
feed, and gives to the lumber a perfect surface by once passing it
through the machine.
The feeding mechanism consists of six rollers, in three pairs, driven by
a strong train of gearing. The upper feeding rollers, with the pressure
rollers over the drum are lifted together in a perfect plane by the
movement of four raising screws, operated by a chain and hand wheel. The
lower feeding rollers always remain in perfect line with the drums.
It is supplied with two polishing cylinders, placed in the body of the
machine, on which the upper frame rests, both having a vibratory lateral
motion for removing lines made by irregularities in the sand paper. The
finishing cylinder is placed so that the discharging rollers carry the
lumber from it, thus running through and finishing one board, if
desired, without another following, and these rollers are arranged for a
vertical adjustment to suit the dressed reduction on the material to be
worked. The roughing cylinder carries a coarse grade of sand paper, and
the finishing one a finer grade. They may be driven in opposite or in
the same direction, as may be necessary. The lower frame is hinged at
each end to the upper frame, so that by removing a pin, either cylinder
can be reached by raising the frame with the screw and worm gear,
operated by a hand wheel at the end of the machine.
A brush attachment (not shown in the cut) is now placed at the end of
the machine just beyond the finishing cylinder, which is a most complete
device for brushing the material clean after it leaves the sand-papering
cylinders.
Fig. 3236 represents a double wheel sanding machine by J. A. Fay & Co.
This machine is intended for accurately finishing the tread of the wheel
ready for the tire, and is one of the most useful and labor-saving
machines that can be placed in a wheel shop.
The frame is built entirely of iron, and has a heavy steel arbor running
in long bearings, with tight and loose pulleys in the centre. On each
end of the arbor is a large sand paper disc for polishing the tread of
the rim.
The wheel to be finished is laid on a rotating carrying frame, having
two upright drivers. These are attached to a jointed swinging frame,
with flexible connections, adjustable to suit wheels of varying
diameters.
The first section of the jointed frame is driven by a shaft and bevel
gears, and swings upon it. The second one has the wheel-carrying frame,
and swings upon the extreme end of the first one, and is driven from it
by a chain connection.
[Illustration: _VOL. II._ SANDING MACHINES. _Plate XXVII._
Fig. 3235.
Fig. 3236.]
A roller wheel is secured at the bottom of the leg, affording a floor
support; also a chain to regulate the proper distance of the wheel from
the discs.
A wrought iron supporting frame is attached upon each side of the sand
paper discs, adjustable for different sizes.
[Illustration: Fig. 3234.]
The wheel when placed in the machine is carried by the gearing against
the sand paper discs, which finishes the tread in the most accurate and
perfect manner.
Machines are made both single and double. The latter are the most
desirable, as the operator has only to place a wheel in position on one
side, when it feeds and takes care of itself.
By the time this is done, the wheel on the opposite side will be
finished and ready to be removed, when a fresh one is put in, and the
operation continued, the only care required being to put in and remove
them. Its capacity is 150 set of wheels per day, and it will do the work
better than can be done by hand.
CHAPTER XXXVI.--BOILERS FOR STATIONARY STEAM ENGINES.
The boiler for a steam engine requires the most careful usage and
inspection, in the first case because a good boiler may be destroyed
very rapidly by careless usage, and in the second case because the
durability of a boiler depends to a great extent upon matters that are
beyond ordinary control, and that in many cases do not make themselves
known except in their results, which can only be discovered by careful
and intelligent inspection. All that the working engineer is called upon
to do is, to use the boiler properly, keep it clean, and examine it at
such intervals as the nature of the conditions under which it is used
may render necessary.
The periods at which a boiler should be cleaned and inspected depend
upon the quality of the water, whether the feed water is purified or
not, and to a certain extent upon the design of the boiler; hence these
periods are variable under different circumstances.
The horse power of a boiler is estimated in various ways, and there is
no uniform practice in this respect. Some makers estimate a boiler to
have a horse power for every fifteen square feet of heating surface it
possesses, while others allow but 12 square feet.
The heating surface of a boiler of any kind is the surface that is
exposed to the action of the fire on one side, and has water on the
other; hence the surface of the steam space is not reckoned as heating
surface, even though it may be exposed to the action of the heat. The
effectiveness of the heating surface of a boiler obviously, however,
depends upon the efficiency of the fire, and this depends upon the
amount of draught, hence the estimation of horse power from the amount
of its heating surface, while affording to a certain extent a standard
of measurement or comparison while the boiler is not in use, has no
definite value when the boiler is erected and at work.
Thus whatever amount of steam a boiler may produce under a poor or
moderate draught, it will obviously produce more under an increased
draught; hence the efficiency of the same boiler depends to a certain
extent upon the draught, or in other words upon the quantity of fuel
that can be consumed upon its fire bars.
The amount of water required in steam boilers varies from 16 lbs. to 40
lbs., per horse power per hour, and it has been proposed to compute the
horse power of boilers from the water evaporation, taking as a standard
30 lbs. of feed water at a temperature of 70 degrees, evaporated into
steam at a temperature of 212 degrees, at which temperature the steam is
assumed to equal the pressure of the atmosphere.
[49]"The strength of the shell of a cylindrical boiler to resist a
pressure within it, is inversely proportional to its diameter and
directly, to the thickness of the plate of which it is formed.
[49] From "_Steam Boilers_."
"For instance, take three cylindrical boilers each made of 1/2 inch
plate, the first one 2 feet 6 inches in diameter; the second twice that,
or 5 feet in diameter; and the third twice that again, or 10 feet in
diameter; and if the 2 foot 6 inch boiler is fit for a safe working
pressure of 180 lbs. per square inch, then the 5 foot boiler will be fit
for exactly one-half that amount, or 90 lbs. per square inch; and the
ten foot boiler will be fit for half the working pressure of the five
foot boiler, hence we have:
-----------------+------------+--------------------------
Diameter of | Thickness |Relative working pressure.
boiler shell. | of plate. |
-----------------+------------+--------------------------
2 feet 6 inches.| 1/2 inch. | 180 lbs. per square inch.
5 " | " " | 90 " " " "
10 " | " " | 45 " " " "
-----------------+------------+--------------------------
"The reverse applies to the thickness of the plate. For instance, if we
take two cylindrical boiler shells, each 5 feet in diameter, the first
one made of plate 1/2 inch thick, and the second twice that, or 1 inch
thick, and if the first is equal to a safe working pressure of 90 lbs.
per square inch, then the second is equal to a safe working pressure of
twice as much, or 180 lbs. per square inch, providing, of course, that
the riveted seams are of equal strength in each case, and that both
boilers are allowed the same margin for safety; hence we have:
----------------+------------+--------------------------
Diameter of | Thickness | Safe working pressure.
boiler. | of shell. |
----------------+------------+--------------------------
5 feet. | 1/2 inch. | 90 lbs. per square inch.
5 " | 1 " | 180 " " " "
----------------+------------+--------------------------
[Illustration: Fig. 3237.]
[Illustration: Fig. 3238.]
"These principles (namely, that the strength of a boiler is, all other
things or elements being equal, inversely proportional to its diameter,
and directly proportional to its thickness) afford us a groundwork upon
which we may lay down rules for determining by calculation the strength
of the solid part[50] of any boiler shell, and the bases of these
calculations are as follows:
[50] In the case of the riveted joints or seams other considerations
come in, as will be shown hereafter.
"If the shell plate of a cylindrical boiler is 1/2 inch thick, there is
one inch section of metal to be broken before the boiler can be divided
into two pieces, that is to say there is 1/2 inch on each side of the
shell, as shown in Fig. 3237, and the two together will make 1 inch. If
we take a ring an inch broad, as, say, at A in Fig. 3238, we shall
obviously have a section of 1 square inch of metal to break before the
ring can be broken into two pieces.
"The next consideration is, what is the average strength of a plate of
boiler iron? Now suppose we have a strip of boiler iron 2 inches wide
and 1/2 inch thick, or, what is the same thing, a bar of boiler iron 1
inch square, and that we lay it horizontally and pull its ends apart
until it breaks, how many lbs. will it bear before breaking? Now for our
present purpose we may assume this to be 47,040 lbs., and if this number
of lbs. be divided by the diameter of the boiler in inches, it will give
the bursting pressure in lbs. for any square inch in the ring, or any
other square inch in the cylindrical shell of the boiler.
"The reason for dividing by the diameter of the boiler is as follows:
[Illustration: Fig. 3239.]
"Of course the steam pressure presses equally on all parts of the
interior surface of the shell, and may be taken as radiating from the
centre of the boiler, as in Fig. 3239, which represents an end view of a
strip an inch wide, of one half of a boiler. Now leaving the riveted
seam out of the question, and supposing the shell to be truly
cylindrical, and the metal to be of equal quality throughout, it will
take just as much pressure to burst the shell apart in one direction as
it will in another, hence we may suppose that the boiler is to be burst
in the direction of arrow _a_, and it is the section of metal at _b_ _b_
that is resisting rupture in that direction.
"Now suppose we divide the surface against which the steam presses into
six divisions, by lines radiating from the centre C, and to find the
amount of area acting on each division to burst the shell in the
direction of arrow _a_, we drop perpendicular lines, as line _e_, from
the lines of division to the line _b_ _b_, and the length of the line
divided off (by the perpendicular) on the diameter represents the
effectiveness of the area of that division to burst the boiler in the
direction of arrow _a_; thus for that part of the boiler surface situate
in the first division, or from _b_ to line _e_, the area acting to burst
the boiler in the direction of _a_ is represented by the length of the
line _k_, while the general direction of the pressure on this part of
the shell is represented by arrow _m_.
"Similarly, for that part of the shell situate between vertical line _e_
and vertical line _f_, the general direction of the steam pressure is
denoted by the arrow _l_, while the proportion of this part that is
acting to sever the boiler in the direction of _a_ is represented by the
distance _n_, or from the line _e_ to line _f_ measured on the line _b_
_b_.
[Illustration: Fig. 3240.]
"By carrying out this process we shall perceive that, although the
pressure acts upon the whole circumference, yet its effectiveness in
bursting the boiler in any one direction is equal to the boiler
diameter. Thus in Fig. 3240, the pressure acting in the direction of the
arrows _a_ (and to burst the boiler apart at _b_ _b_) is represented by
the diametral line _b_ _b_, while the pressure actually exerted upon the
whole boiler shell is represented by the circumference of the boiler.
"To proceed, then, it will now be clear that the ultimate strength of
the boiler material, multiplied by twice the thickness of the boiler
shell plate in inches or decimal parts of an inch, and this sum divided
by the internal diameter of the boiler, in inches, gives the pressure
(in lbs. per square inch) at which the boiler shell will burst."
We have here only considered the strength of the solid plate of the
shell, and may now consider the strength of the riveted joints, because,
as the boiler cannot be any stronger as a whole than its weakest part
is, and as the riveted joints are the weakest parts of a cylindrical
boiler,[51] therefore the strength of the riveted joint determines the
strength of the boiler.
[51] It may be here noted that the riveted joint of a flat plate is
stronger than the flat surface of the plate, because at the joint the
plate is doubled, or one plate overlaps the other.
[52]"The strains to which a riveted joint is subjected are as follows:
That acting to shear the rivet across its diameter is called the
_shearing_ strain. But the same strain acts to tear the plate apart;
hence, when spoken of with reference to the action on the plate, it is
called the _tearing_ strain.
[52] From "_Steam Boilers_."
"The same strain also acts to crush and rupture the plate between the
rivet hole and the edge of the plate, and in this connection it is
called the _crushing_ strain.
[Illustration: Fig. 3241.]
"Thus, Fig. 3241 represents a single riveted lap joint, in which the
joint at rivets A, B, and C is intact, the metal outside of D has
crushed, the rivets E, F have sheared, and the plate has torn at H,
leaving a piece J on the rivets K L.
"It is obvious that, since it is the same strain that has caused these
different kinds of rupture, the joint has, at each location, simply
given way where it was the weakest.
[Illustration: Fig. 3242.]
"If a riveted joint was to give way by tearing only, the indication
would be that the proportion of strength was greatest in the rivets,
which might occur from the plate being of inferior metal to the rivets,
or from the rivets being too closely spaced. If the rivets were to shear
and the plate remain intact, it would indicate insufficient strength in
the rivets, which might occur from faulty material in the rivets, from
smallness of rivet diameter, or from the rivets being too widely spaced.
"The object then, in designing a riveted joint is to have its
resistance to tearing and shearing proportionately equal, whatever form
of joint be employed."
The English Board of Trade recommends that the rivet section should
always be in excess of the plate section, whereas, in ordinary American
practice, for stationary engine boilers, the plate and rivet percentages
are made equal.
The forms of riveted joints employed in boiler work are as follows:
[Illustration: Fig. 3243.]
[Illustration: Fig. 3244.]
Fig. 3242 represents a single riveted lap joint. Fig. 3243 represents a
double riveted lap joint, chain riveted; and Fig. 3244, a double riveted
lap joint, with the rivets arranged zigzag.
[Illustration: Fig. 3245.]
[Illustration: Fig. 3246.]
Fig. 3245 represents a single and Fig. 3246 a double riveted butt joint,
so called because the ends of the boiler plate abut together. The plates
on each side of joint are called butt straps.
The advantages of the butt joint are, first, that the boiler shell is
kept more truly cylindrical, and the joint is not liable to bend as it
does in the lap joints, in the attempt of the boiler (when under
pressure) to assume the form of a true circle, and second that the
rivets are placed in double shear. That is to say, if in a lap joint the
rivet was to shear between the plates, the joint would come apart,
whereas, in a butt joint, the rivet must shear on each side of the
plate, and therefore in two places.
[Illustration: Fig. 3247.]
Fig. 3247 represents a form of joint much used in locomotive practice in
the United States. It is a lap joint, with a covering plate on the
inside of the joint; rivets E and F are in single and rivets D in double
shear.
[53]"When we have to deal with comparatively thin boiler plates, there
is no difficulty in obtaining a sufficiently high percentage of strength
in the joints, by using the ordinary double riveted joint, but when we
have to deal with thick plates, as in the case of large marine boilers,
as 1 inch or upwards, a more costly form of joint must be employed, in
order to obtain the required percentage of strength at the joint; hence
the ordinary double riveted joint is replaced by various other forms as
follows:
[53] From "_Steam Boilers_."
[Illustration: Fig. 3248.]
"First, a triple zigzag riveted lap joint, such as shown in Fig. 3248,
or a chain riveted joint as in Fig. 3249, in both of which the third row
of rivets enables the rivet pitch to be increased, thus increasing the
plate percentage, while the third row of rivets also increases the rivet
percentage.
"Second, by employing butt joints with butt straps, either double or
treble riveted.
[Illustration: Fig. 3249.]
[Illustration: Fig. 3250.]
[Illustration: Fig. 3251.]
[Illustration: Fig. 3252.]
"A double riveted butt joint with double straps is shown in Fig. 3250,
and a treble with double straps in Figs. 3251 and 3252.
"Third. By various arrangements of the rivets in conjunction with butt
joints and double straps, with which it is not necessary, at this point,
to deal.
"One of the great advantages obtained by the use of the double strap is
that of bringing the rivet into double shear (or in other words, the
rivet must shear on each side of the plate, or in two places, instead of
between the plates only, before the joint can give way by shearing), and
thus obtaining an increased calculated strength of 1-3/4 times the
ordinary or single shear, the rule being to find the rivet strength in
the ordinary way (as before explained), and then multiply the result by
1.75.
"The Board of Trade rules for spacing the rivets of these joints are as
follows:
"Dimension E is the distance from the edge of the plate to the centre of
the rivet hole. Dimension V is the distance between the rows of rivets,
dimension _p_ is the pitch of the rivets, which is always measured from
centre to centre of the rivets, and dimension _pd_ is the diagonal pitch
of the rivets.
"The rule for finding dimension E, whether the plates and rivets are
either of steel or iron, is as follows:
"Multiply the diameter of the rivet by 3 and divide by 2, the formula
being as follows:
3 × _d_
------- = E.
2
"To find the distance V between the rows of rivets in chain riveted
joints. This distance must not be less than twice the rivet diameter,
and a more desirable rule is four times the rivet diameter plus 1
divided by 2, thus:
4_d_ + 1
-------- = V.
2
"To find the distance between the rows of zigzag riveted joints:
_____________________________
\/(11_p_ + 4_d_) × (_p_ + 4_d_)
------------------------------- = V,
10
that is, multiply 11 times the pitch plus 4 times the rivet diameter, by
the pitch plus 4 times the rivet diameter, then extract the square root
and divide by 10.
"To find diagonal pitch _pd_, multiply the pitch _p_ by 6, then add 4
and divide by 10, thus:
6_p_ + 4
-------- = _pd_."
10
[Illustration: Fig. 3253.]
Fig. 3253 represents a form of high percentage joint, used upon marine
boilers of 10 to 14 feet diameter, and carrying from 100 to 190 lbs.
pressure of steam. The rivets are what are termed unevenly pitched, or,
that is to say, on each side of the joint, there are three rows of
rivets, of which the inner and outer rows are wider pitched than the
middle row.
[54]"The advantage gained by this spacing is that the shear of the outer
row of rivets is added to the plate section at the narrow pitch, that is
to say, if the plate section broke through the line of rivet holes at
the narrow pitch, it has yet to shear the outer row of rivets before the
plate can separate."
[54] From "_Steam Boilers_."
[Illustration: Fig. 3254.]
Fig. 3254 represents a second example of joint with rivets unevenly
pitched, this form finding much favor in recent practice. The four inner
rows of rivets are spaced at narrow pitch and the two outer rows are
wide pitched.
[55]"The strength percentage of this joint is calculated from three
points of view, as follows:
[55] From "_Steam Boilers_."
"First. The plate section at the wide pitched rivets.
"Second. The rivet section in one pitch.
"Third. The plate section at the narrow pitch plus half the double shear
of the outer or wide pitched rivet."
The steam pressures generally employed in the boilers of stationary
engines range from about 60 to 100 lbs. per square inch, and as a result
of these comparatively low pressures less perfect forms of construction
are employed than would be permissible if higher pressures were used.
The strength of the shell plate of boilers of small diameter is always
largely in excess of the requirements, and as a result the strength of
the joints may bear a very low percentage to that of the solid plate,
and yet give a sufficient factor of safety for the working pressure.
Take, for example, a boiler shell of 36 inches internal diameter with a
shell plate 1/4 inch thick, and allowing the strength of the material to
be 48,000 lbs. per inch of section, and with a factor of safety of 4,
the working pressure will be 166 lbs. per square inch, thus:
Strength Plate thickness
of the material. × 2.
48000 × (.25 × 2)
--------------------------------- = 666-2/3 lbs. = bursting pressure.
36
Diameter of boiler.
By dividing this 666 by the factor of safety 4 we get 166-2/3 lbs. as
the working pressure of the shell plate independent of the riveted
joint. Usually, however, such a boiler would not be used for a pressure
above about 60 lbs. per inch, and this leaves a wide margin for the
reduction of strength caused by the riveted joints.
Suppose, for example, that a single riveted lap joint is used, and the
strength of this joint is but 50 per cent. of that of the solid plate,
and we have as follows:
Strength of % strength Twice
material. of riveted the plate
joint. thickness.
48000 × .50 × (.25 × 2)
---------------------------------- = 83-1/3 lbs. = W.P.
36 × 4
Internal diam. Factor of
of boiler. safety.
Here then we find that the working pressure of the solid plate is double
that of the riveted joint, and that the working pressure of the boiler
is 83 lbs. per square inch, notwithstanding that the strength of the
riveted joints is but 50 per cent. of that of the solid plate. Such a
boiler would not, however, be used for a pressure of over 60 lbs. per
square inch.
If the above-named boiler was double riveted so as to bring the
percentage of joint strength up to say 70 per cent, of that of the solid
plate, its working pressure would be 116 lbs. per square inch, thus:
Strength of % strength Twice
material of riveted the plate
joint. thickness.
48000 × .70 × (.25 × 2)
---------------------------------- = 116-2/3 lbs. = W.P.
36 × 4
Internal diam. Factor of
of boiler. safety.