[Illustration: Fig. 1565.]
Fig. 1565 represents a planer by William Sellers and Co., of
Philadelphia, Pennsylvania. This planer is provided with an automatic
feed to the sliding head, both horizontally and vertically, and with
mechanism which lifts the apron, and therefore the cutting tool, during
the backward stroke of the work table, and thus prevents the abrasion of
the tool edge that occurs when the tool is allowed to drag during the
return stroke. The machine is also provided with a quick return motion,
and in the larger sizes with other conveniences to be described
hereafter.
The platen or table is driven by a worm set at such an angle to the
table rack as to enable the teeth of the rack to stand at a right angle
to the table length, and as a result the line of thrust between the worm
and the rack is parallel to the [V]-guideways, which prevents wear
between the [V]s of the table and of the bed.
The driving pulleys are set at a right angle to the length of the
machine, their planes of revolution being, therefore, parallel to the
plane of revolution of the line or driving shaft overhead, and parallel
with the lathes and other machines driven from the same line of
shafting, thus taking up less floor space, while the passage ways
between the different lines of machines is less obstructed.
By setting the worm driving shaft at an angle the teeth of the worm
rotate in a plane at a right angle to the length of the work-table rack,
and as a result the teeth of the worm have contact across the full width
of the rack teeth instead of in the middle only, as is the case when the
axis of a worm is at a right angle to the axis of the wheel or rack that
it drives.
Furthermore, by inclining the worm shaft at an angle the teeth of the
rack may be straight (and not curved to suit the curvature of the worm
after the manner of worm-wheels), because the contact between the worm
and rack teeth begins at one side of the rack and passes by a rolling
motion to the other, after the manner and possessing the advantages of
Hook's gearing as described in the remarks made with reference to
gear-wheel teeth.
By inclining the worm shaft, however, the side thrust incidental to
Hook's gearing is avoided, the pressure of contact of tooth upon tooth
being in the same direction and in line with the rack motion. As the
contact between the worm teeth and the rack is uniform in amount and is
also continuous, a very smooth and uniform motion is imparted to the
work table, and the vibration usually accompanying the action of
spur-gearing is avoided.
The worm has four separate spirals or teeth, hence the table rack is
moved four teeth at each worm revolution, and a quick belt motion is
obtained by the employment of pulleys of large diameter.
It is desirable that the belt motion of a planing machine be as quick as
the conditions will permit, because the amount of power necessary to
drive the machine can thus be obtained by a narrower belt, it being
obvious that since the driving power of the belt is the product of its
tension and velocity the greater the velocity the less the amount of
tension may be to transmit a given amount of power.
The mechanism for shifting the belt to reverse the direction of table
motion is shown in Fig. 1566 removed from all the other mechanism.
To the bracket or arm B are pivoted the arms or belt guides C and D and
the piece G. In the position occupied by the parts in the figure the
belt for the forward or cutting stroke would be upon the loose pulley
P´, and that for the quick return stroke would be upon the loose pulley
P, hence the machine table would remain at rest. But suppose the rod F
be moved by hand in the direction of arrow _f_, then G would be moved
upon its pivot X, and its lug _h_ would meet the jaw _i_ of C, moving C
in the direction of arrow _a_, and therefore carrying the belt from
loose pulley P´ on to the driving pulley P´´, which would start the
machine work table, causing it to move in the direction of arrow W until
such time as the stop A meets the lug R, operating lever E and moving
rod F in the direction of arrow _d_. This would move G, causing its lug
_h_ to meet the jaw _j_, which would move C from P´´ back to the
position it occupies in the figure, and as the motion of G continued its
shoulder at _g´_ would meet the shoulder or lug T of K (the latter being
connected to D) and move arm D in the direction of _b_, and therefore
carrying the crossed belt upon P, and causing the machine table to run
backward, which it would do at a greater speed than during the cutting
traverse, because of the overhead pulley on the countershaft being of
greater diameter than that for the cutting stroke.
It is obvious that since each belt passes from its loose pulley to the
fast one, the width of the overhead or countershaft pulleys must be
twice as wide as the belt, and also that to reverse the direction of
pulley revolution one driving belt must be crossed; and as on the
countershaft the smallest pulley is that for driving the cutting stroke,
its belt is made the crossed one, so as to cause it to envelop as much
of the pulley circumference as possible, and thereby increase its
driving power. The arrangement of the countershaft pulleys and belts is
shown in Fig. 1567, in which S is the countershaft and N, O the fast and
loose pulleys for the belt from the line shaft pulley; Q´ is the pulley
for operating the table on the cutting stroke (with the crossed belt),
while Q is the pulley for operating the table on its return stroke. The
difference in the speed of the table during the two strokes is obviously
in the same proportions as the diameters of pulleys Q´ and Q.
The feed rod, and feed screw, and rope for lifting the tool on the back
stroke are operated as follows:--
Fig. 1568 is an end view of the mechanism viewed from the front of the
machine, and Fig. 1569 is a side view of the same.
The shaft of the driving pulleys (P P´ and P´´, Fig. 1567) drives a
pinion operating the gear wheel W, upon the face of which is a serrated
internal wheel answering to a ratchet wheel, and with which a pawl
engages each time the direction of pulley revolution (or, which is the
same thing, the direction of motion W) reverses, and causes the pawl and
the shaft, to which the plate P, Fig. 1569, is fast, to make one-half a
revolution, when the pawl disengages and all parts save the wheel W come
to rest.
From this plate P the feed motions are actuated, and the tool is lifted
during the back traverse of the work table by the following mechanisms.
[Illustration: Fig. 1566.]
[Illustration: Fig. 1567.]
[Illustration: Fig. 1568.]
[Illustration: Fig. 1569.]
[Illustration: Fig. 1570.]
Referring to Fig. 1570, upon the plate P is pivoted a lever Q, carrying
a universal joint at Z, and a nut pivoted at V, and it is obvious that
at each half-revolution of P, the rod R is moved vertically. This rod
connects to a universal joint J (shown in Fig. 1571) that is pivoted in
a toothed segment (K, in the same figure) which engages with a pinion on
the feed screw, this pinion being provided with a ratchet and feed pawl
(of the usual construction) for reversing the direction of the feed or
throwing it out of action.
The amount of feed is regulated as follows:--
Referring to Figs. 1569 and 1570, the amount of vertical motion of rod R
is obviously determined by the distance of the universal joint Z from
the centre of the plate P, and this is set by operating the hand wheel
T, which revolves the screw Y in the nut V.
For lifting the tool during the return motion of the work and work
table, there is provided in the plate P, Fig. 1570, a pin which actuates
the rod B, which in turn actuates the grooved segment C.
[Illustration: Fig. 1571.]
From this segment a cord is stretched passing over the grooved pulley D,
Fig. 1571, thence over pulley E, and after taking a turn around the
pulley F, Fig. 1571, it passes to the other end of the cross slide,
where it is secured.
This pulley F is therefore revolved at each motion of the plate P, Figs.
1569 or 1570, or in other words each time the work table reverses its
motion.
In reference to Figs. 1571 and 1572, F, Fig. 1571, is fast upon a pin
_g_, at whose other end is a pinion operating a gear-wheel _h_. Upon the
face of this gear-wheel is secured a steel plate shown at _m_ in Fig.
1572, which is a vertical section of the sliding head. In a cam groove
in _m_, projects a pin that is secured to the sleeve _n_, which envelops
the vertical feed screw O. This sleeve _n_ has frictional contact at _p_
with the bar _q_, whose lower end receives the bell crank _r_, which on
each return stroke is depressed, and thus moves the tool apron _s_, and
with it the tool, which is therefore relieved from contact with the cut
upon the work.
The self-acting vertical feed is actuated as follows:--
Referring to Figs. 1571 and 1572 the gear segment K operates a pinion
upon the squared end of the feed rod L, this pinion L having the usual
pawl and ratchet for reversing the direction of rod revolution.
The splined feed rod L actuates the bevel pinion M, which is in gear
with bevel pinion N, the latter driving pinion P, which is threaded to
receive the vertical feed screw O; hence when P is revolved it moves the
feed screw O endways, and this moves the vertical slide R upon which is
the apron box T and the apron _s_. To prevent the possibility of the
friction of the threads causing the feed screw O to revolve with the
pinion P, the journal _e_ of the feed screw O is made shorter than its
bearing in R, so that the nut _f_ may be used to secure the feed screw O
to the slide R.
PLANER SLIDING HEADS.--In order that the best work may be produced, it
is essential that the sliding head of a planer or planing machine be
constructed as rigid as possible, and it follows that the slides and
slideways should be of that form that will suffer the least from wear,
resist the tool strain as directly as possible, and at the same time
enable the taking up of any wear that may occur from the constant use of
the parts.
Between the tool point that receives the cutting strain and the cross
bar or cross slide that resists it there are the pivoted joint of the
apron, the sliding joint of the vertical feed, and the sliding joint of
the saddle upon the cross slide, and it is difficult to maintain a
sliding fit without some movements or spring to the parts, especially
when, as in the case of a planer head, the pressure on the tool point is
at considerable leverage to the sliding surfaces, thus augmenting the
strain due to the cut.
The wear on the cross slide is greater at and towards the middle than at
the ends, but it is also greater at the end nearest to the operator than
at the other end, because work that is narrower than the width of the
planing machine table is usually chucked on the side nearest to the
operator or near the middle of the table width, because it is easier to
chuck it there and more convenient to set the tool and watch the cut,
for the reason that the means for stopping and starting the machine, and
for pulling the feed motions in and out of operation, are on that side.
The form of cross bar usually employed in the United States is
represented in Fig. 1573, and it is clear that the pressure of the cut
is in the direction of the arrow _c_, and that the fulcrum off which the
strain will act on the cross bar is at its lowest point _d_, tending to
pull the top of the saddle or slider in the direction of arrow _e_,
which is directly resisted by the vertical face of the gib, while the
horizontal face _f_ of the gib directly resists the tendency of the
saddle to fall vertically, and, therefore, the amount of looseness that
may occur by reason of the wear cannot exceed the amount of metal lost
by the wear, which may be taken up as far as possible by means of the
screws _a_ and _b_, which thread through the saddle and abut against the
gib. The gib is adjusted by these screws to fit to the least worn and
therefore, the tightest part of the cross bar slideway, and the saddle
is more loosely held at other parts of the cross bar in proportion as
its slideway is worn.
[Illustration: Fig. 1572.]
In this construction the faces of the saddle are brought to bear over
the whole area of the slideways surface of the cross bar, because the
bevel at _g_ brings the two faces at _m_ into contact, and the set-screw
_b_ brings the faces in together. Instead of the screws _a_ and _b_
having slotted heads for a screw driver, however, it is preferable to
provide square-headed screws, having check nuts, as in Fig. 1574, so
that after the adjustment is made the parts may be firmly locked by the
check nuts, and there will be no danger of the adjustment altering.
The wear between the slider and the raised slideways S is taken up by
gibs and screws corresponding to those at _a_ and _c_ in the Fig. 1575,
and concerning these gibs and screws J. Richards has pointed out that
two methods may be employed in their construction, these two methods
being illustrated in Figs. 1575 and 1576, which are taken from
"Engineering."
In Fig. 1575 the end _s_ of the adjustment screw _a_ is plain, and is
let into the gib _c_ abutting against a flat seat, and as a result while
the screw pressure forces the gib _c_ against the bevelled edge of the
slideway it does not act to draw the surfaces together at _m_ _m_ as it
should do. This may be remedied by making the point of the screw of such
a cone that it will bed fair against gib _c_, without passing into a
recess, the construction being as in Fig. 1576, in which case the screw
point forces the gib flat against the bevelled face and there is no
tendency for the gib to pass down into the corner _e_, Fig. 1575, while
the pressure on the screw point acts to force the slide _a_ down upon
the slideway, thus giving contact at _m_ _m_.
The bearing area of such screw points is, however, so small that the
pressure due to the tool cut is liable to cause the screw to indent the
gib and thus destroy the adjustment, and on this account a wedge such as
shown in Fig. 1577 is preferable, being operated endwise to take up the
wear by means of a screw passing through a lug at the outer or exposed
end of the wedge.
The corners at _i_, Figs. 1575 and 1576, are sometimes planed out to the
dotted lines, but this does not increase the bearing area between the
gib _c_ and the slide, while it obviously weakens the slider and renders
it more liable to spring under heavy tool cuts.
Fig. 1578 represents a form of cross bar and gib found in many English
and in some American planing machines. In this case the strain due to
the cut is resisted directly by the vertical face of the top slide of
the cross bar, the gib being a triangular piece set up by the screws at
_a_, and the wear is diminished because of the increased wearing
surface of the gib due to its lower face being diagonal.
[Illustration: Fig. 1573.]
[Illustration: Fig. 1574.]
[Illustration: Fig. 1575.]
[Illustration: Fig. 1576.]
On the other hand, however, this diagonal surface does not directly
resist the falling of the saddle from wear, and furthermore in taking up
the wear the vertical face of the saddle is relieved from contact with
the vertical face of the cross bar, because the screws _a_ when set up
move the top of the saddle away from the cross bar, whereas in Fig.
1573, setting up screw _b_ brings the saddle back upon the vertical face
of the cross bar slideway.
[Illustration: Fig. 1577.]
[Illustration: Fig. 1578.]
[Illustration: Fig. 1579.]
Fig. 1579 is a front view, and Fig. 1580 a sectional top view, of a sunk
vertical slide, corresponding to that shown in Figs. 1573 and 1578, but
in this case the gib has a tongue _t_, closely fitted into a recess or
channel in the vertical slider S, and to allow room for adjustment, the
channel is made somewhat deeper than the tongue requires when newly
fitted. The adjustment is effected by means of two sets of screws, _a_
and _b_, of which the former, being tapped into the gib, serve to
tighten, and the latter, being tapped into the slide, serve to loosen
the gib. By thus acting in opposite directions the screws serve to check
each other, holding the gib rigidly in place. To insure a close contact
of the gib against the vertical surface of the slide, the screws _b_ are
placed in a line slightly outside of the line of the screws _a_.
Fig. 1581 represents a similar construction when the slideways on the
swing frame project outwards, instead of being sunk within that frame.
Fig. 1582 represents the construction of the Pratt & Whitney Company's
planer head, in which the swivel head instead of pivoting upon a central
pin and being locked in position by bolts, whose nuts project outside
and on the front face of the swing frame, is constructed as follows:--
A circular dovetail recess in the saddle receives a corresponding
dovetail projection on the swivel head or swing frame, and the two are
secured together at that point by a set-screw A. In addition to this the
upper edge B of the saddle is an arc of a circle of which the centre is
the centre of the dovetail groove, and a clamp is employed to fasten the
swivel head to the saddle, being held to that head by a bolt, and
therefore swinging with it. Thus the swivel head is secured to its
saddle at its upper edge, as well as at its centre, which affords a
better support.
The tool box is pivoted upon the vertical slider, and is secured in its
adjusted position by the bolts _n_ in Fig. 1573, the object of swinging
it being to enable the tool to be lifted on the back stroke and clear
the cut, when cutting vertical faces, as was explained with reference to
shaping machines.
The tool apron is in American practice pivoted between two jaws, which
prevent its motion sideways, and to prevent any play or lost motion
that might arise from the wear of the taper pivoting pin _b_, in Fig.
1583, the apron beds upon a bevel as at _a_, so that in falling to its
seat it will be pulled down, taking up any lost motion upon _b_.
[Illustration: Fig. 1580.]
[Illustration: Fig. 1581.]
[Illustration: Fig. 1582.]
[Illustration: Fig. 1583.]
[Illustration: Fig. 1584.]
[Illustration: Fig. 1585.]
The bevel at _a_ would also prevent any side motion to the apron should
wear occur between it and the jaws. In addition to this bevel, however,
there may be employed two vertical bevels _c_ in the top view in Fig.
1584. In English practice, and especially upon large planing machines,
the apron is sometimes made to embrace or fit the outsides of the tool
box, as in Fig. 1585, the object being to spread the bearings as wide
apart as possible, and thus diminish the effect of any lost motion or
wear of the pivoting pin, and to enable the tool post or holder to be
set to the extreme edge of the tool box as shown in the figure.
It is desirable that the tool apron bed as firmly as possible back
against its seat in the tool box, and this end is much more effectively
secured when it is pivoted as far back as possible, as in Fig. 1585,
because in that case nearly all the weight of the apron, as well as that
of the tool and its clamp, acts to seat the apron, whereas when the
pivot is more in front, as _m_, in Fig. 1573, it is the weight of the
tool post and tool only that acts to keep the apron seated.
In small planing machines it is a great advantage to provide an extra
apron carrying two tool posts, as in Fig. 1586, so that in planing a
number of pieces, that are to be of the same dimension, one tool may be
used for roughing and one for finishing the work. The tools should be
wider apart than the width of the work, so that the finishing tool will
not come into operation until after the roughing tool has carried its
cut across.
When the roughing tool has become dulled it should, after being ground
up, be set to the last roughing cut taken, so that it will leave the
same amount of finishing cut as before.
The advantage of this system is that the finishing tool will last to
finish a great many pieces without being disturbed, and as a result the
trouble of setting its cut for each piece is avoided; on which account
all the pieces are sure to be cut to the same dimension without any
further measuring than is necessary for the first piece, whereas if one
tool only is used it rapidly dulls from the roughing cut, and will not
cut sufficiently smooth for the finishing one, and must therefore be
more frequently ground up to resharpen it, while it must be accurately
set for each finishing cut. A double tool apron of this kind is
especially serviceable upon such work as planing large nuts, for it will
save half the time and give more accurate work.
In some planing machines, and notably those made by Sir Joseph
Whitworth, a swiveling tool holder is made so that at each end of the
stroke the cutting tool makes half a revolution, and may therefore be
used to cut during both strokes of the planer table. A device answering
this purpose is shown in Fig. 1587. The tool-holding box is pivoted upon
a pin A, and has attached to it a segment of a circular rack or
worm-wheel, operated by a worm upon a shaft having at its upper end the
pulley shown, so that by operating this pulley, part of a revolution at
the end of each work-table stroke, one or the other of the two tools
shown in the tool box, is brought into position to carry the cut along.
Thus two tools are placed back to back, and it is obvious that when the
tool box is moved to the right, the front tool is brought into position,
while when it is moved to the left, the back or right-hand tool is
brought into position to cut, the other tool being raised clear of the
work.
[Illustration: Fig. 1586.]
[Illustration: Fig. 1587.]
The objections to either revolving one tool or using two tools so as to
cut on both strokes are twofold: first, the tools are difficult to set
correctly; and, secondly, the device cannot be used upon vertical faces
or those at an angle, or in other words, can only be used upon surfaces
that are nearly parallel to the surface of the work table.
[Illustration: Fig. 1588.]
[Illustration: Fig. 1589.]
Figs. 1588 and 1589 represent the sliding head of the large planer at
the Washington Navy Yard, the sectional view, Fig. 1589, being taken on
the line X X in Fig. 1588. C is the cross bar and S the saddle, F being
the swing frame or fiddle, as some term it, and S´ the vertical slider;
B is the tool box, and A the apron.
The wear of the cross slider is taken up by the set screws _a_, and that
of the vertical slide by the screws _b_.
The graduations of the degrees of a circle for setting over the swing
frame F, as is necessary when planing surfaces that are at an angle to
the bed and to the cross slide, are marked on the face of the saddle,
and the pointer (_f_, Fig. 1578) is fastened to the edge of the swing
frame. When the swing frame is vertical the pointer is at 90° on the
graduated arc, which accords with English practice generally. In
American practice, however, it is customary to mark the graduations on
the edge of the swing frame as in Fig. 1590, so that the pointer stands
at the zero point _o_ when the swing frame is vertical, and the
graduations are marked on the edge of the swing frame as shown, the zero
line _o_ being marked on the edge of the saddle.
In the English practice the swing frame is supposed to stand in its
neutral or zero position when it is vertical, and all angles are assumed
to be measured from this vertical zero line, so that if the index point
be set to such figure upon the graduated arc as the angle of the work is
to be to a vertical line, correct results will be obtained.
Thus in Fig. 1591 (which is from _The American Machinist_) the pointer
is set to 40° and the bevelled face is cut to an angle of 40° with the
vertical face as marked. But if the head be graduated as in Fig. 1592,
the face of the planer table being taken as the zero line _o_, then the
swing frame would require to be set over to 30° out of its normal or
neutral vertical position as is shown in figure, the bevelled face being
at an angle of 50° from a vertical, and 40° from a horizontal line,
hence the operator requires to consider whether the number of degrees of
angle are marked on the drawing from a zero line that is vertical on one
that is horizontal.
[Illustration: Fig. 1590.]
[Illustration: Fig. 1591.]
[Illustration: Fig. 1592.]
[Illustration: Fig. 1593.]
[Illustration: Fig. 1594.]
Referring again to Fig. 1588 the slots for the tool post extend fully
across the apron, so that the tool posts may be set at any required
point in the tool-box width, and the tool or tool holder may be set
nearer to the edge of the tool box than is the case when fixed bolts, as
in Fig. 1590, are used, because these bolts come in the way.
This is mainly important when the tool is required to carry a deep
vertical cut, in which case it is important to keep the tool point as
close in to the holder as possible so that it may not bend and spring
from the pressure of the cut.
The tool or holder may be held still closer to the edge of the head, and
therefore brought still closer to the work, when the apron embraces the
outside of the tool box, as was shown in Fig. 1585, and referred to in
connection therewith.
[Illustration: Fig. 1595.]
[Illustration: Fig. 1596.]
A sectional side view and a top view of Fig. 1588 through the centre of
the head is given in Figs. 1595 and 1596, exposing the mechanism for the
self-acting feed traverse, and for the vertical feed. For the feed
traverse the feed screw (_m_, Fig. 1588) passes through the feed nut N.
For the vertical feed the feed rod (_n_, Fig. 1588) drives a pair of
bevel-gears at P, which drives a second pair at Q, one of which is fast
on a spindle which passes through the vertical feed screw, and is
secured thereto by the set screw _e_. The object of this arrangement is
that if the self-acting vertical feed should be in action and the tool
or swing frame S´ should meet any undue obstruction, the set screw _e_
will slip and the feed would stop, thus preventing any breakage to the
gears at P or Q. The feed screw is threaded into the top of S´. At E is
the pin on which the tool box pivots to swing it at an angle.
The mechanism for actuating the cross-feed screw and the feed rod is
shown in the top view, Fig. 1597, and the side view, Fig. 1598, in which
A is a rod operated vertically and actuated from the stop (corresponding
to stop R in Fig. 1558) that actuates the belt shifting gear. Upon A is
the sleeve B, which actuates rod C, which operates the frame D. This
frame is pivoted upon a stud which is secured to the cross bar C, and is
secured by the nut at E. Frame D carries pawls F and G, the former of
which engages gear-wheel H, which drives the pinion _n_, Fig. 1598, that
is fast on the feed rod, while the latter drives the gear K, which in
turn drives pinion P, which is fast upon the feed screw in Fig. 1588.
The feeds are put into or thrown out of action as follows:--On the same
shaft or pin as the pawls G and F, is secured a tongue T, Fig. 1599,
whose end is wedge shaped and has a correspondingly shaped seat in a
plate V, whose cylindrical stem passes into a recess provided in D, and
is surrounded by a spiral spring which acts to force V outwards from the
recess.
[Illustration: Fig. 1597.]
[Illustration: Fig. 1598.]
[Illustration: Fig. 1599.]
In the position shown in the figure the end of T is seated in the groove
in V, and the pressure of the spring acts to hold T still and keep the
pawl G from engaging with the teeth of gear-wheel H. But suppose the
handle W (which is fast on the pawl G) is pulled upwards, and T will
move downwards, disengaging from the groove in V, and the upper end of
pawl G will engage with the teeth of H, actuating in the direction of
the arrow during the upward motion of rod A, and thus actuating pinion
_n_ and putting the vertical feed in motion in one direction. When the
rod A makes its downward stroke the pawl G will slip over the teeth of
H, because there is nothing but the spiral spring to prevent the end of
the pawl from slipping over these teeth. To place the vertical feed in
action in the other direction, handle W is pressed downwards, causing
the bottom end X of the pawl to engage with the teeth of H.
PLANER BEDS AND TABLES.--The general forms of the beds of small planers
are such as in Figs. 1557 and 1558, and those of the larger sizes such
as shown in Fig. 1563.
It is of the first importance that the [V]-guideways in these beds
should be straight and true, and that the corresponding guides on the
planer table should fit accurately to those in the bed; for which
purpose it is necessary, if the greatest attainable accuracy is to be
had, that the guideways in the bed first be made correct, and those on
the table then fitted, using the bed to test them by.
The angle of these guides and guideways ranges from about 60° in the
smallest sizes to about 110° in the largest sizes of planers. Whatever
the angle may be, however, it is essential that all the angles be
exactly equal, in order that the fit of the table may not be destroyed
by the wear.
In addition to this, however, it is important that each side of the
guides stand at an equal height, or otherwise the table will not fit,
notwithstanding that all the angles may be equal.
[Illustration: Fig. 1600.]
Suppose, for example, that in Fig. 1600 all the sides are at an equal
angle, but that side _e_ was planed down to the dotted line _e_, then
all the weight of the table would fall on side _a_, and, moreover, the
table would be liable to rock in the guideways, for whenever the
combined weight of the table and the pressure of the cut was greatest on
the right-hand of the middle _x_ of the table width and the feed was
carried from right to left, then the table would move over, as shown
exaggerated in Fig. 1601, because the weight would press guide _g_ down
into its guideways, and guide _h_ would then rise up slightly and not
fit on one side at all, while on the other side it would bear heaviest
at point _p_. Great care is therefore necessary in planing and fitting
these guides and ways, the processes for which are explained under the
respective headings of "Examples in Planer Work," and "Erecting
Planers."
In some designs the bed and table are provided with but one
[V]-guideway, the other side of the table being supported on a flat
side, and in yet another form the table is supported on two flat
guideways.
Referring to the former the bearing surface of the [V] and of the flat
guide must be so proportioned to that of the [V] that the wear will let
the table down equally, or otherwise it would become out of parallel
with the cross slide, and would plane the work of unequal thickness
across its width.
[Illustration: Fig. 1601.]
[Illustration: Fig. 1602.]
Referring to the second, which is illustrated in Fig. 1602, it possesses
several disadvantages.
[Illustration: Fig. 1603.]
Thus, if there be four gibs as at A, B, and E, F, set up by their
respective set-screws, the very means provided to take up the wear
affords a means of setting the bed out of line, so that the slots in the
table (and, therefore, the chucks fitting to these slots) will not be in
the line of motion of the table, and the work depending upon these
chucks will not be true. This may be avoided by taking up the wear on
two edges only, as in Fig. 1603 at A, B, but in this case the bearing at
E and F would eventually cease by reason of the wear.
Suppose, for example, that the pressure of the tool cut tends to throw
the table in the direction of arrow J, and the surfaces at A and F
resist the thrust and both will wear. But when the strain on the table
is in the direction of arrow K, the surfaces B, E, will both wear; hence
while the width apart of the table slides becomes greater, the width
apart of the bed slideways wears less, and the fit cannot be maintained
on the inner edges of the guideways. It is furthermore to be noted that
with flat guideways the table will move sideways very easily, since
there is nothing but the friction of the slides to prevent it, but in
the case of [V]-guides the table must lift before it can move sideways;
hence, it lies very firmly in its seat, its weight resisting any side
motion.
[Illustration: Fig. 1604.]
It is found in practice that the wear of the guides and guideways in
planer tables and beds is greatest at the ends, and the reason of this
is as follows:--
In Fig. 1604 is a top view of a planer table, the cutting tool being
assumed to be at T, and as the driving gear is at G forcing the table in
the direction of the arrow A, and the resistance is at T, the tendency
is to throw the table around in the direction of arrows B and C. When
the tool is on the other side of the middle of the table width as at F,
the tendency is to throw the table in the opposite direction as denoted
by the arrows D and E, which obviously causes the most wear to be at the
ends of the slides.
As the feed motions are placed on the right-hand side of the machines
the operator stands on that side of the machine at X, and starts the cut
from that side of the table; hence unless the work is placed in the
middle of the table width, the wear will be most in the direction of
arrows B and C.
The methods of fitting the guideways and guides of planer beds and
tables is given in the examples of erecting.
[Illustration: Fig. 1605.]
A very good method of testing them, however, is as follows:--Suppose
that we have in Fig. 1605 a plate that has been planed on both edges G,
H, and that in consequence of a want of truth in the planer guideways
edge G is rounding and edge H hollow, the plate being supposed to lie
upon the planer table in the position in which it was planed.
[Illustration: Fig. 1606.]
Now, suppose that it be turned over on the planer, as in Fig. 1606, the
rounding edge, instead of standing on the right-hand side of the planer
table, will stand on the left-hand side, so that if that edge were
planed again in its new position it would be made hollow instead of
rounding in its length. It is obvious, therefore, that if a planed edge
shows true when turned over on the planer table, the [V]s of the planer
are true, inasmuch as the table moves in a straight line in one
direction, which is that affecting the truth of all surfaces of the work
that are not parallel to the cross feed of the tool, or, what is the
same thing, parallel to the surface of the planer table.
PLANING MACHINE TABLES.--In order that the guides on the table of a
planer may not unduly wear, it is essential that they be kept well
lubricated, which is a difficult matter when the table takes short
strokes and has work upon it that takes a long time to perform, in which
case it is necessary to stop the planing operations and run the work
back so as to expose the guideways in the bed, so that they may be
cleaned and oiled.
[Illustration: Fig. 1607.]
It will often occur that the work will not pass beneath the cross slide,
and in that case it should be raised out of the ways to enable proper
oiling, because insufficient lubrication frequently causes the guides
and guideways to tear one another, or cut as it is commonly termed.
[Illustration: Fig. 1608.]
The means commonly employed for oiling planer [V]s or guideways are as
follows:--At the top of the guideways small grooves, _g_ _g_, Fig. 1609,
are provided, and at the bottom a groove _x_. In the guides on the table
there are provided pockets or slots in which are pivoted pendulums of
the form shown in Fig. 1607 at A. Each pendulum passes down to the
bottom of groove _x_ in which the oil lies, and is provided on each side
with recesses _e_, which are also seen in the edge view on the right of
the figure.
The pendulums are provided with a long slot to enable them when the
table motion reverses to swing over and drag in the opposite direction
(as shown in Fig. 1607); as they drag on the bottom of groove _x_ of the
bed they lift the oil it contains, which passes up the sides of the
pendulum as denoted by the arrow, and into grooves provided on the
surface of the table guide, as at _h_ in Fig. 1608, in which V´ is the
table guide, V the guideway in the bed, _g_ oil grooves, (see sectional
view, Fig. 1613), _x_ the oil groove at the bottom of the bed V, and _h_
_h_ the oil grooves which receive the oil the pendulum lifts.
The oil grooves _h_ on the table guide run into the grooves _g_ in the
[V]-guideway in the bed, hence grooves _g_ _g_ become filled with oil.
But after the end of the table has passed and left the bed V exposed,
the oil flows out of grooves _g_ down the sides of the guideway, and
constant lubrication is thus afforded at all times when the stroke of
the table is sufficient to enable the pendulums to force the oil
sufficiently far along oil way _h_. When the table reverses the pendulum
will swing over and lift the oil up into grooves or oil ways _h´_.
[Illustration: Fig. 1609.]
[Illustration: Fig. 1610.]
Another and excellent method of oiling, also invented by Mr. Hugh
Thomas, of New York, is shown in Figs. 1609 and 1610, in which P
represents an oiling roll or wheel, [V]-shaped, to correspond to the
shape of the [V]s. This roll is laced with cotton wick or braid, as
shown by the dark zigzag lines, and is carried in a frame _f_, capable
of sliding vertically in a box C, which is set in a pocket in the bed V,
and contains oil. By means of a screw S, the roll P is set to touch the
face of the table [V], and the friction between the roll and the [V], as
the table traverses, rotates the roll, which carries up the oil and
lubricates the table [V] over its whole surface. The dust, &c., that may
get into the oil settles in the bottom of the box C, which can
occasionally be cleaned out. In this case the oil is not only presented
to the oil grooves (_h_, Fig. 1608), but spread out upon the [V]s; but
it is nevertheless advisable to have the grooves _h_ so as to permit of
an accumulation of oil that will aid in the distribution along the [V]s
of the bed.
This method of oiling has been adopted in some large and heavy planers
built by R. Hoe & Co., and has been found to operate admirably, keeping
the guides and guideways clean, bright, and well lubricated.
Mr. Thomas has also patented a system of forced oil circulation for
large planers. In this system a pump P, Fig. 1611, draws the oil from
the cellars C (which are usually provided on the ends of planer beds)
and delivers it through pipes passing up to the sides of the [V]s, thus
affording a constant flow of oil. A reservoir at the foot of the pump
enables the dirt, &c., in the oil to settle before it enters the pump,
which can be operated from any desirable part of the planer mechanism.
The pendulums are also used in connection with the forced circulation.
As the work is fastened to the upper face of a planing machine table
either directly or through the intervention of chucking devices, the
table must be pierced with holes and grooves to receive bolts or other
appliances by means of which the work or chuck, as the case may be, may
be secured.
For receiving the heads of bolts, [T]-shaped grooves running the full
length of the table are provided, and in addition there are sometimes
provided short [T]-grooves, to be shown presently.
For receiving stops and other similar chucking devices, the tables are
provided with either round or square holes.
In Fig. 1612 is shown a section of a table provided with [T]-grooves and
rows of round holes, _a_, _b_, _c_, _d_, _e_, which pass entirely
through the table, and hence must not be placed so that they will let
dirt fall through to the [V]-guides or the rack. Tables with this
arrangement of holes and grooves are usually used upon small planers in
the United States, and sometimes to large ones also.
[Illustration: Fig. 1611.]
[Illustration: Fig. 1612.]
[Illustration: Fig. 1613.]
It is obvious that the dirt, fine cuttings, &c., will pass through the
holes and may find its way to the [V]-guideways. Especially will this be
the case when water is used upon the tool to take smooth cuts upon
wrought iron and steel. To obviate this the construction shown in Fig.
1613 is employed.
Fig. 1613 represents a section of one guideway of a table and bed. On
each side of the table [V] there is cut a groove leaving projecting ribs
_b_, _c_, and whatever water, oil, or dirt may pass through the holes
(Fig. 1612), will fall off these points _b_, _c_, Fig. 1613, and thus
escape the guideways, while falling dust will be excluded by the wings
_b_, _c_, from the [V]s.
[Illustration: Fig. 1614.]
The capacity of a planer table may be increased by fitting thereto two
supplementary short tables, as shown in Fig. 1614, several applications
of its use being given with reference to examples in planer work. These
supplementary tables are secured to the main table by set-screws at A,
and have been found of great value for a large variety of work,
especially upon planing machines in which the table width is
considerably less than the width between the uprights or stanchions.
[Illustration: Fig. 1615.]
Fig. 1615 represents the arrangement of square holes and [T]-grooves
employed upon large planers. The square holes are cast in the table, and
are slightly tapered to receive taper plugs or stops against which the
work may abut, or which may be used to wedge against, as will be
hereafter described, one of these stops being shown at S in the figure.
[Illustration: Fig. 1616.]
The [T]-shaped slots _f_, _g_, _h_, are to receive the heads of bolts as
shown in Fig. 1616. The bolt head is rounded at corners _a_, _b_, and
the square under the head has the corresponding diagonal corners as _c_
also rounded, so that the width of the head being slightly less than
that of the slot it may be passed down in the slot and then given a
quarter revolution in the direction of the arrow, causing the wings of
the head to pass under the recess of the [T]-groove, as shown in Fig.
1617, which is a sectional end view of the groove with the bolt in
place. The square corners at _e_ and at _f_ prevent the bolt from
turning round more than the quarter revolution when screwing up the bolt
nut, and when the nut is loosened a turn the bolt can be rotated a
quarter revolution and lifted out of the groove.
Now it is obvious that these slots serve the same purpose as the
longitudinal [T]-grooves, since they receive the bolt heads, and it
might therefore appear that they could be dispensed with, but it is a
great convenience to be able to adjust the position of the bolt across
the table width, which cannot be done if longitudinal grooves only are
employed. Indeed, it might easily occur that the longitudinal grooves
be covered by the work when the short transverse ones would serve to
advantage, and in the wide range of work that large planers generally
perform, it is desirable to give every means for disposing the bolts
about the table to suit the size and shape of the work.
[Illustration: Fig. 1617.]
It is obvious that the form of bolt head shown in Fig. 1616 is equally
applicable to the longitudinal grooves as to the cross slots, enabling
the bolt to be inserted, notwithstanding that the work may cover the
ends of the longitudinal slots.
The round holes _a_, _b_, _c_, &c., in Fig. 1612, are preferable to the
square ones, inasmuch as they weaken the table less and are equally
effective. Being drilled and reamed parallel the plugs that fit them may
be passed through them to any desirable distance, whereas the square
plugs being taper must be set down home in their holes, necessitating
the use of plugs of varying length, so that when in their places they
may stand at varying heights from the table, and thus suit different
heights of work. Whatever kind of holes are used it is obvious that they
must be arranged in line both lengthways of the table and across it, so
that they will not come in the way of the ribs R, which are placed
beneath it to strengthen it.
The longitudinal grooves are planed out to make them straight and true
with the [V]-guides and guideways, so that chucking appliances fitting
into the grooves may be known to be set true upon the table.
[Illustration: Fig. 1618.]
[Illustration: Fig. 1619.]
In Fig. 1618, for example, is shown an angle piece A having a projection
fitting into a longitudinal groove, the screws whose heads are visible
passing through A into nuts that are in the widened part of the groove,
so that operating the screws secures A to the table. The vertical face
of A being planed true, a piece of work, as a shaft S, may be known to
be set in line with the table when it is clamped against A by clamps as
at P, or by other holding devices. Angle pieces such as A are made of
varying lengths and heights to suit different forms and sizes of work.
In some planing machine tables a [V]-groove is cut along the centre for
the purpose of holding spindles to have featherways or splines cut in
them, the method of chucking being shown in Fig. 1619. This, however, is
not a good plan, as the bolts and plates are apt to bend the shaft out
of straight, so that the groove cut in the work will not be straight
when the spindle is removed from the clamp pressure. The proper method
of chucking such work will, however, be given in connection with
examples on planer work.
For the round holes in planer tables several kinds of plugs or stops are
employed, the simplest of them being a plain cylindrical plug or stop.
[Illustration: Fig. 1620.]
Fig. 1620 represents a stop provided with a screw B. The stem A fits
into the round holes, and the screw is operated to press against the
work. By placing the screw at an angle, as shown, its pressure tends to
force the work down upon the planer table.
[Illustration: Fig. 1621.]
A similar stop, termed a bunter screw, S, Fig. 1621, may be used in the
longitudinal slots, the shape of its hook enabling it to be readily
inserted and removed from the slot. These screws may be applied direct
to the work when the circumstances will permit, or a wedge W may be
interposed between the screw and the work, as shown.
[Illustration: Fig. 1622.]
Fig. 1622 represents a form of planer chuck used on the smaller sizes of
planers, and commonly called planer centres. A is the base or frame
bolted to the planer table at the lugs L; at B is a fixed head carrying
what may be termed the live centre D, and C is a head similar to the
tailstock of a lathe carrying a dead centre; F is an index plate having
worm-teeth on its edge and being operated by the worm G. At S is a
spring carrying at its end the pin for the index holes. To bring this
pin opposite to the requisite circle of holes, the bolt holding S to A
is eased back and S moved as required. On the live centre D is a clamp
for securing the work or mandrel holding dog. Head C is split as shown,
and is held to the surface of A by the bolt H, which is tapped into the
metal on one side of the split.
It is obvious that polygons may be planed by placing the work between
the centres and rotating it by means of G after each successive side of
the polygon has been planed or shaped, the number of sides being
determined by the amount of rotation of the index plate.
[Illustration: Fig. 1623.]
Fig. 1623 shows a useful chuck for holding cylindrical work, such as
rolls. The base is split at E, so that by means of the bolt and nut D
the [V]-block a may be gripped firmly; B and C are screws for adjusting
the height of the [V]-block A. At F is the bolt for clamping the chuck
to the planer table, and G is a cap to clamp the work W in the block A.
It will be seen that this chuck can be set for taper as well as parallel
work.
[Illustration: Fig. 1624.]
[Illustration: Fig. 1625.]
Fig. 1624 represents a chucking device useful for supporting or packing
up work, or for adjusting it in position ready to fasten it to the work
table, it being obvious that its hollow seat at A enables it to set
steadily upon the table, and that its screw affords a simple means of
adjusting its height. It may also be used between the jaws of a
connecting rod strap or other similar piece of work to support it, as in
Fig. 1625, and prevent the jaws from springing together under the
pressure of the tool cut.
[Illustration: Fig. 1626.]
Another and very useful device for this purpose is shown in Fig. 1626,
consisting of a pair of inverted wedges, of which one is dovetailed into
the other and having a screw to operate them endwise, the purpose being
to hold the two jaws the proper distance apart and prevent their closure
under pressure of the planer vice jaws. It is obvious that the device in
Fig. 1625 is most useful for work that has not been faced between the
jaws, because the device in Fig. 1626 would, upon rough work that is not
true, be apt to spring the work true with the inside faces, which may
not be true with the outside ones, and when the wedges were removed the
jaws would spring back again, and the work performed while the inverted
wedges were in place would no longer be true when they were removed.
[Illustration: Fig. 1627.]
Fig. 1627 represents a centre chuck to enable the cutting of spirals.
The principle of the design is to rotate the work as it traverses, and
this is accomplished as follows:--
Upon the bed of the machine alongside of the table is bolted the rack A
A, into which gears the pinion B, which is fixed to the same shaft as
the bevel-gear C, which meshes with the bevel-wheel D. Upon the same
shaft as D is the face plate E, and in the spindle upon which D and E
are fixed is a centre, so that the plate E answers to the face plate of
a lathe. F is a bearing for the shaft carrying B and C, and G is a
bearing carrying the spindle to which E and D are fixed. H is a standard
carrying the screw and centre, shown at I, and hence answers to the
tailstock of a lathe. K represents a frame or plate carrying the
bearings F and G, and the standard H. L represents the table of the
planing machine to which K is bolted. The reciprocating motion of the
table L causes the pinion B to revolve upon the rack A A. The pinion B
revolves C, which imparts its motion to D, and the work W being placed
between the centres as shown, is revolved in unison with E, revolving in
one direction when the table K is going one way, and in the other when
the motion of the table is reversed; hence a tool in the tool post will
cut a spiral groove in the work.
To enable the device to cut grooves of different spirals or twist, all
that is necessary is to provide different sizes of wheels to take the
places of C and D, so that the revolutions of E, and hence of the work
W, may be increased or diminished with relation to the revolutions of B;
or, what is the same thing, to a given amount of table movement, or a
stud may be put in so as to enable the employment of change gears.
[Illustration: Fig. 1628.]
Figs. 1628 and 1629 represent a universal planer chuck, designed and
patented by John H. Greenwood, of Columbus, Ohio, for planing concave or
convex surfaces, as well as ordinary plane ones, with the cross feed of
the common planer.
The base L of the chuck is bolted to the planer work table in the
ordinary manner.
The work-holding frame or vice is supported, for circular surfaces, by
being pivoted to the base at O, O, and by the gibbed head D, which has
journal bearing at E. The work is held between the stationary jaw _b_ or
_b´_ (at option) and the movable jaw C which may face either _b_ or _b´_
(by turning C round). Suppose then, that while the chuck is passing the
cutting tool, end I of the work-holding frame is raised, lifting that
end of the work above the horizontal level (the work-holding frame
swinging at the other end on the pivots O, O), then the tool will
obviously cut a convex surface. Or if end I of the work-holding frame be
lowered while the cut is proceeding, the tool will cut a concave
surface.
[Illustration: Fig. 1629.]
Now end I is caused to rise or lower as follows:--The head D is adjusted
by means of its gibs to be a sliding fit on the bar G in Fig. 1629,
which bar is rigidly fixed at P to the planer bed; hence as the planer
table and the chuck traverse, D slides along bar G. If this bar is fixed
at an angle to the length of the planer head, D must travel at that same
angle, causing end I of the work-holding frame to rise or lower (from O,
O, as a centre of motion) as it traverses according to the direction of
motion of the planer table.
Suppose that in Fig. 1629, the planer table is moving on the back or
non-cutting stroke, then head D will be moving towards the point of
suspension P of the bar G, and will therefore gradually lower as it
proceeds, thus lowering end I of the work-holding frame and causing the
curved link to pass beneath the tool with a curved motion or suppose the
table to be on its cutting traverse, then head D will be raised as the
table moves and the cut proceeds, and the surface cut by the tool will
be concave.
Now, suppose that the bar G were fixed at an angle, with its end, that
is towards the back end of the planer, inclined towards the table
instead of away from it as in Fig. 1629, and then on the cutting
traverse head D would cause end I (Fig. 1628) of the work-holding vice
or frame to lower as the cut proceeded, and the tool would therefore
plane a convex surface.
Thus the direction of the angle in which G is fixed governs whether the
surface planed shall be a concave or a convex one, and it is plain that
the amount of concavity or convexity will be governed and determined by
the amount of angle to which G is set to the planer table.
When the chuck is not required to plane curved surfaces the bar G is
altogether dispensed with, and the chuck becomes an ordinary one
possessing extra facilities for planing taper work.
Thus for taper work the work-holding frame may be set out of parallel
with the base of the chuck to an amount answering to the required amount
of taper, being raised or lowered (as may be most convenient) at one end
by means of the gears M, of which there is one on each side meshing into
the segmental rack shown, the work-holding frame being secured in its
adjusted position by means of a set bolt.
To set the work-holding frame parallel for parallel planing, a steady
pin is employed, the frame being parallel to the base when that pin is
home in its place.
The construction of the chuck is solid, and the various adjustments may
be quickly and readily made, giving to it a range of capacity and
usefulness that are not possessed by the ordinary forms of planer
chucks.
PLANING MACHINE BEDS.--In long castings such as lathe or planer beds,
the greatest care is required in setting the work upon the planer table,
because the work will twist and bend of its own weight, and may have
considerable deflection and twist upon it notwithstanding that it
appears to bed fair upon the table. To avoid this it is necessary to
know that the casting is supported with equal pressure at each point of
support. In all such work the surface that is to rest upon the
foundation or legs should be planed first.
[Illustration: Fig. 1630.]
Thus supposing the casting in Fig. 1630 to represent a lathe shears, the
surfaces _f_ whereon the lathe legs are to be bolted should be planed
first, the method of chucking being as follows:--
[Illustration: Fig. 1631.]
The bed is balanced by two wedges A, in Fig. 1630, one being placed at
each end of the bed, and the position of the wedges being adjusted so
that it lies level. A line coincident with the face of the bed (as face
_d_) is then drawn across the upper face of each wedge. Wedges (as B,
C,) are then put in on each side of the bed until they each just meet
the bed, and a line coincident with the bed surface is drawn across
their upper surfaces. Wedge B is then driven in until it relieves A of
the weight of the bed, and a second line is drawn across its upper face.
It is then withdrawn to the first line, and the wedge on the opposite
side of the bed is driven in until A is relieved of the weight, when a
second line is drawn on this wedge's face. The wedges at the other end
(as C) are then similarly driven in and withdrawn, being also marked
with two lines, and then the four wedges (B, C, and the two
corresponding ones on the opposite side of the bed) are withdrawn,
having upon their surfaces two lines each (as A, B, in Fig. 1631).
Midway between these two lines a third (as C) is drawn, and all four
wedges are then driven in until line C is coincident with the bed
surface, when it may be assumed that the bed is supported equally at all
the four points. When the bed is turned over, surfaces _f_ may lie on
the table surface without any packing whatever, as they will be true.
Another excellent method is to balance the bed on three points, two at
one end and one at the other, and to then pack it up equally at all four
corners.
To test if the surface of a piece of such work has been planed straight,
the following plan may be pursued:--
[Illustration: Fig. 1632.]
Suppose that surface E, Fig. 1632, is to be tested, it having been
planed in the position it occupies in the figure, and the casting may be
turned over so that face E stands vertical, as in Fig. 1632, and a tool
may be put in the tool post of the planer, the bed being adjusted on the
planer table so that the tool point will just touch the surface at each
end of the bed. The planer table is then run so that the tool point may
be tried with the middle of the bed length, when, if the face E is true,
it will just meet the tool point at the middle of its length as well as
at the ends.
In the planing of the [V]-guides and guideways of a bed for a machine
tool, such as, for example, a planer bed and table, the greatest of care
is necessary, the process being as follows:--
Beginning with the bed it has been shown in Fig. 1601 that the sides of
the guideways must all be of the same height as well as at the same
angle, and an excellent method of testing this point is as follows:--
[Illustration: Fig. 1633.]
In Fig. 1633 is shown at A a male gauge for testing the [V]-guideways in
the bed, and at B a female gauge for testing those on the table. These
two gauges are accurately made to the correct angle and width, and
fitted together as true as they can be made, being corrected as long as
any error can be found, either by testing one with the other or by the
application of a surface plate to each separate face of the guides and
guideways. The surfaces C and D of the respective gauges are made
parallel with the [V]-surfaces, a point that is of importance, as will
be seen hereafter. It is obvious that the female gauge B is turned
upside down when tried upon the table.
[Illustration: Fig. 1634.]
Suppose it is required to test the sides _e_, _f_, of the bed guideways
in Fig. 1634, and the gauge must be pulled over in the direction of the
arrow so that it touches those two sides only; a spirit-level laid upon
the top of the gauge will then show whether the two faces _e_, _f_, are
of equal height. It is obvious that to test the other two faces the
gauge must be pulled over in the opposite direction.
This test must be applied while fitting the [V]s to the gauge. Suppose,
for example, that when the gauge is applied and allowed to seat itself
in the ways, the two outside angles _e_, _g_, are found to bear while
the two inside ones do not touch the gauge at all, then by this test it
can be found whether the correction should be made by taking a cut off
_e_ or off _g_, for if the spirit-level stood level when the gauge was
pulled in either direction, then both faces would require to be operated
upon equally, but suppose that the gauge and spirit-level applied as
shown proved end _e_ to be high, then it would be the one to be operated
on, or if when the gauge was pulled over in the opposite direction end
_g_ was shown (by the spirit-level) to be high, then it would be the one
to be operated upon.
By careful operation the table and bed may thus be made to fit more
perfectly than is possible by any other method. To test the fit of the
gauge to the [V]s it is a good plan to make a light chalk mark down each
[V] and to then apply the gauge, letting it seat itself and moving it
back and forth endways, when if it is a proper fit it will rub the chalk
mark entirely out. It may be noted, however, that a light touch of red
marking is probably better than chalk for this purpose.
It is of importance that the [V]s be planed as smooth as possible, and
to enable this a stiff tool holder holding a short tool, as in Fig. 1635
should be used, the holder being held close up to the tool box as shown.
It will be obvious that when the head is set over to an angle it should
be moved along the cross slide to plane the corresponding angle on the
other side of the bed.
Fig. 1636 represents a planer chuck by Mr. Hugh Thomas. The angle piece
A is made to stand at an angle, as shown, for cylindrical work, such as
shafts, so that the work will be held firmly down upon the table. The
base plate B has ratchet teeth at each end C, into which mesh the pawls
D, and has slotted holes for the bolts which hold it down to the table,
so that it has a certain range of movement to or from the angle piece A,
and may therefore be adjusted to suit the diameter or width of the work.
The movable jaw E is set up by the set-screw F and is held down by the
bolts shown. The pawls D are constructed as shown in Fig. 1637, the pin
or stem S fitting the holes in the planer table and the tongue P being
pivoted to the body R of the pawl. As the pawls can be moved into any of
the holes in the table, the base plate B may be set at an angle,
enabling the chuck to be used for taper as well as for parallel work,
while the chuck has a wide range of capacity.
In Fig. 1614 is shown a supplementary table for increasing the capacity
of planer tables, and which has already been referred to, and Fig. 1638
represents an application of the table as a chucking device. A, A, &c.,
are frames whose upper surfaces are to be planed. An angle plate is
bolted to the planer table and the supplementary table is bolted to the
angle plate. The first frame is set against the vertical face of the
supplementary table, and the remaining ones set as near as possible, B,
B, &c., being small blocks placed between the frames which are bolted to
the planer table as at C.
[Illustration: Fig. 1635.]
In many cases this method of chucking possesses great advantages. Thus
in the figure there are six frames to be planed, and as they would be
too long to be set down upon the planer table, only three or four could
be done at a time, and a good deal of measuring and trying would be
necessary in order to get the second lot like the first. This can all be
avoided by chucking the whole six at once, as in figure.
Another application of the same tables as useful chucking devices is
shown in Fig. 1639, where two frames E, F, are shown bolted to the
machine table and supported by the supplementary tables T, which are
bolted to the main table and supported by angle-pieces _b_, _b_. Work
that stands high up from the planer table may be very effectively
steadied in this way, enabling heavier cuts and coarser feeds while
producing smoother work.
[Illustration: Fig. 1640.]
As horizontal surfaces can be planed very much quicker than vertical
ones, it frequently occurs that it will pay to take extra trouble in
order to chuck the work so as to plane it horizontally, an excellent
example being the planing of the faces of the two halves of a large
pulley, the chucking of which is illustrated in Fig. 1640.
Four pieces, as at A, are made to engage the rims of the two halves of
the pulley and hold them true, one with the other. The two plates T´ and
T´´ are set under the pulley halves to level the upper faces, and wooden
clamps C, C, are bolted up to hold the pulleys together at the top, W
representing wedges between the hubs. S represents supports to block up
the pulley near its upper face, and at P are clamps to hold the two
halves to the table. It is found that by this method of chucking more
than half the time is saved, and the work is made truer than it is
possible to get it by planing each half separately and laying them down
on the table.
Supplemental tables may also be made in two parts, the upper one being
capable of swiveling as in Fig. 1641, the swiveling device corresponding
to that shown for the Thomas shaper chuck in Fig. 1530. This enables the
work to be operated upon on several different faces without being
released from the chuck. Thus in figure the segment could be planed on
one edge and the upper table swiveled to bring the other edge in true
with the table, which would be a great advantage, especially if the face
it is chucked by has not been trued.
Figs. 1642 and 1643 show other applications of the same swiveling
device.
It is obvious that the chuck shown in Fig. 1636 can be mounted on a
supplemental and swiveling table as shown in Fig. 1644, thus greatly
facilitating the chucking of the work and facilitating the means of
presenting different surfaces or parts of the work to the tool without
requiring to unchuck it. The pawls, also, may in heavy work have two
pins to enter the work-table holes and be connected by a strap as in
Fig. 1645.
In the exigencies of the general machine shop it sometimes happens that
it is required to plane a piece that is too wide to pass between the
uprights of the planing machine, in which case one standard or upright
may be taken down and the cross slide bolted to the other, as in Fig.
1646, the blocks _a_, _a_, being necessary on account of the arched form
of the back of the cross slide. In the example given the plates to be
planed were nearly twice as wide as the planer table and were chucked as
shown, the beam D resting on blocks E, F, and forming a pathway for the
piece C, which was provided with rollers at each end so as to move
easily upon D. The outer end of the plate was clamped between B and C,
and the work was found to be easily and rapidly done. In this chucking,
however, it is of importance that beam D be carefully levelled to stand
parallel with the planer table face, while its height must be so
adjusted that it does not act to cant or tilt the table sideways as that
would cause one [V] of the planer ways to carry all or most of the
weight, and be liable to cause it to cut and abrade the slide surfaces.
[Illustration: _VOL. I._ =EXAMPLES IN PLANING WORK.= _PLATE XVIII._
Fig. 1636.
Fig. 1637.
Fig. 1638.
Fig. 1639.]
[Illustration: Fig. 1641.]
[Illustration: Fig. 1642.]
[Illustration: Fig. 1643.]
[Illustration: Fig. 1644.]
[Illustration: Fig. 1645.]
[Illustration: Fig. 1646.]
CUTTING TOOLS FOR SHAPING AND PLANING MACHINES.--All the cutting tools
forged to finished shape from rectangular bar steel, and described in
connection with lathe work, are used in the planer and in the shaper,
and the principles governing the rake of the top face remain the same.
But in the matter of the clearance there is the difference that in a
planing tool it may be made constant, because the tool feeds to its cut
after having left the work surface at the end of the back stroke, hence
the clearance remains the same whatever the amount or rate of feed may
be.
[Illustration: Fig. 1647.]
On this account it is desirable to use a gauge as a guide to grind the
tool by, the application of such a gauge being shown in Fig. 1647. It
consists of a disk turned to the requisite taper and laid upon a plate,
whereon the tool also may be laid to test it. The tool should not be
given more than 10° of clearance, unless in the case of broad flat-nosed
tools for finishing, for which 5° are sufficient.
[Illustration: Fig. 1648.]
[Illustration: Fig. 1649.]
The principle of pulling rather than pushing the tool to its cut, can,
however, be more readily and advantageously carried out in planer than
in lathe tools, because the spring of the tool and of the head carrying
it only need be considered, the position of the tool with relation to
the work being otherwise immaterial. As a consequence it is not unusual
to forge the tools to the end of pulling, rather than of pushing the
cutting edge.
[Illustration: Fig. 1650.]
In Figs. 1648 and 1649, for example, are two tools, W representing the
work, and A the points off which the respective tools will spring in
consequence of the pressure; hence the respective arrows denote the
direction of the tool spring. As a result of this spring it is obvious
the tool in Fig. 1648 will dip deeper into the work when the pressure of
the cut increases, as it will from any increase of the depth of the cut
in roughing out the work, or from any seams or hard places in the metal
during the finishing cut. On the other hand, however, this deflection or
spring will have the effect of releasing the cutting edge of the tool
from contact with the work surface during the back stroke, thus
rendering it unnecessary to lift the tool to prevent the abrasion, on
its back stroke, from dulling its cutting edge.
[Illustration: Fig. 1651.]
[Illustration: Fig. 1652.]
It will be noted that the radius from the point of support A is less for
the tool in Fig. 1649 than for that in Fig. 1648, although both tools
are at an equal height from the work, which enables that in Fig. 1649 to
operate more firmly. In these two figures the extremes of the two
systems are shown, but a compromise between the two is shown in Fig.
1650, the cutting edge coming even with the centre of the body of the
steel, which makes the tool easier to forge and grind, and keeps the
cutting edge in plainer view when at work, while avoiding the evils
attending the shape shown in Fig. 1648.
It is sometimes necessary, however, that a tool of the form in Fig. 1652
be used, as, for example, to shape out the surface of a slot, and when
this is the case the tool should be shaped as in Fig. 1651, the bottom
face having ample clearance (as, say, 15°) from the heel A to about the
point B, and about 3° from B to the front end. The front face should
have little or no clearance, because it causes the tool to dig into the
work. A tool so shaped will clear itself well on the back stroke,
whereas if but little clearance and front rake be given as in Fig. 1652,
the tool will not only dig in, but its cutting edge will rub on the back
or return stroke.
[Illustration: Fig. 1653.]
For broad feed finishing cuts the shape of tool shown in Fig. 1653 is
employed, the cutting edge near the two corners being eased off very
slightly with the oilstone. The amount of clearance should be very
slight indeed, only just enough to enable the tool to cut as is shown in
the figure, by the line A A. The amount of front rake may be varied to
suit the nature and hardness of the metal, and the tool should be held
as close in as possible to the tool clamp.
Smoother work may be obtained in shaping and in planing machine tools
when the tool is carried in a holder, such as in Fig. 1654, which is
taken from _The American Machinist_ because in this case any spring or
deflection either in the tool or in the shaper head acts to cause the
tool to relieve itself of the cut instead of digging in, as would be the
case were the tool put in front of the tool post as in Fig. 1654. In
finishing large curves this is of great importance, because to obtain
true and smooth curves it is necessary to shape the tool to cut upon the
whole of the curve at once, and this gives so great a length of cutting
edge, that the tool is sure to chatter if held in front of the tool
post.
[Illustration: Fig. 1654.]
It is essential, therefore, to carry the tool at the back of the tool
post as shown, and for curves that are arcs of circles tools such as in
Fig. 1655 may be employed, or a circular disk will answer, possessing
the advantage that its shape may be maintained by grinding its flat face
to resharpen it.
Cutters of the kind shown in Fig. 1655 may be made to possess several
important advantages aside from their smooth action: thus they may be
made after the principle explained with reference to the Brown & Sharpe
rotary cutters for gear-teeth, in which case the front face only need be
ground to resharpen them, and their shapes will remain unaltered, and
they may be given different degrees of front rake by placing packing
between one side and the holder, and any number of different shaped
cutters may be fitted to the same stock.
[Illustration: Fig. 1655.]
TOOL HOLDERS FOR PLANING MACHINES.--The advantages of tool holders for
planing machines are equally as great as those already described for
lathes, but as applied to planing machines there is the additional
advantage that the clearance necessary on the tool is less variable for
planer work than for lathe work, because in lathe work the diameter of
the work as well as the rate of tool feed affects the tool clearance,
whereas in planer work the tool feed is put on before the tool begins
its cutting action; hence the degree of clearance is neither affected by
the size of the work nor by the rate of feed, and as a result the tools
may be given a definite and constant amount of clearance.
[Illustration: Fig. 1656.]
Fig. 1656 represents a planer tool holder (by Messrs. Smith & Coventry),
in which what is, in effect, a swivel tool post is attached to the end
of the holder, thus enabling the tool to be used on either the right or
left-hand of the holder at will. The shape of the tool steel is shown in
section on the right-hand of the engraving, being narrow at the bottom,
which enables the tool to be very firmly held and reduces the area to be
ground in sharpening the tool. A side and end view of the holder is
shown in Fig. 1657, in which it is seen that the tool may be given top
rake or angle to render it suitable for wrought iron or steel or may be
set level for brass work.
[Illustration: Fig. 1657.]
In Fig. 1658 the tool and holder are shown in position on the planer
head, the front rake on the tool being that suitable for wrought iron.
[Illustration: Fig. 1658.]
It is to be noted, however, that the amount of front rake should, to
obtain the best results, be less for steel than for wrought iron, and
less for cast iron than for wrought, while for brass there should be
none; hence the tool post should be made to accomplish these different
degrees of rake in order to capacitate such holders for the four
above-named metals. It is an advantage, however, that by inclining the
tool to give the top rake, this rake may be kept constant by grinding
the end only of the tool to sharpen it, and as the end may be ground to
a gauge it is very easy to maintain a constant shape of tool.
Furthermore as the tool is held by one binding screw only, it may be
more readily adjusted in position for the work than is the case when the
two apron clamp nuts require to be operated.
[Illustration: Fig. 1659.]
[Illustration: Fig. 1660.]
Figs. 1659 to 1661, show this tool-holder applied to various kinds of
work, thus in Fig. 1659 the tool is planing under the underneath side of
a lathe bed flange, while in Fig. 1660 it is acting upon a [V]-slideway
and escaping an overhanging arm, and in Fig. 1661 it is shown operating
on a [V]-slideway and in a [T]-groove.
[Illustration: Fig. 1661.]
Fig. 1662 represents a tool holder by Messrs. Bental Brothers, the tool
being held in a swivelled tool post, so that it may be used as a right
or left-hand tool. In this case the front rake must be forged or ground
on the tool, and there is the further objection common to many tool
holders, that the tool if held close in to the tool post is partly
hidden from view, thus increasing the difficulty of setting it to the
depth of cut.
[Illustration: Fig. 1662.]
Another form of planer or shaper tool-holder is shown in Fig. 1663, in
which a tool post is mounted on a tool bar, and may be used as a right
or left-hand tool at will.
[Illustration: Fig. 1663.]
[Illustration: Fig. 1664.]
Fig. 1664 represents a tool holder in which two tools may be held as
shown, or a single tool right-hand or left-hand as may be required, or
the tool may be held at the end of the holder as in Fig. 1665. The
advantage of such a holder is well illustrated in the case of cutting
out a [T]-shaped groove, because with such a holder a straight tool can
be used for the first cuts, its position being shown in Fig. 1665,
whereas in the absence of such a holder a tool bent as in Fig. 1666
would require to be used, this bend giving extra trouble in the forging,
rendering the tool unfit for ordinary plain work, and being unable to
carry so heavy a cut or to cut so smooth as the straight tool in Fig.
1665. In cutting out the widest part of such a groove the advantage of
the holder is still greater, because by its use a tool with one bend, as
in Fig. 1667, will serve, whereas without a holder the tool must have
two bends, as shown in the figure, and would be able to carry a very
light cut, while liable to dig into the work and break off.
[Illustration: Fig. 1665.]
[Illustration: Fig. 1666.]
The tool itself should be so forged that one side is flush with the side
of the tool steel as shown at A in Fig. 1668, for if there is a
shoulder, as at C, it sometimes prevents the tool from entering the work
as shown in the figure.
[Illustration: Fig. 1667.]
Other examples in the use of this tool holder are given in Figs. 1669
and 1670.
[Illustration: Fig. 1668.]
In Fig. 1669, we have the case of cutting out the [V]-slideways of a
planer bed, and it is seen that the tool point may be held close to the
holder, the side of the tool box still clearing the side of the
[V]-slideway, whereas in the absence of the holder the tool would
require to have a considerable bend in it, or else would have to stand
out from the bottom of the tool apron to a distance equal to the length
of one side of the slideway.
[Illustration: Fig. 1669.]
[Illustration: Fig. 1670.]
In Fig. 1670 it is also seen that by the use of the holder the tool
point may also be held as close as necessary to the holder, and still
permit the side of the vertical slide S´ and the tool box B to clear the
vertical face of the work.
In all planer work it is an essential in the production of true and
smooth surfaces that the tool be held as close in to the tool clamp or
tool box as possible, and this forms one of the main advantages of tool
holders.