The Lathe has now for many years been steadily making its way from
the workshops of our leading artisans to those of the amateur and
lesser stars of the mechanical world. This is but the natural result
of the various additions and improvements which have been introduced
into its construction from time to time. The unworkmanlike and
clumsy tool of olden days has long since been superseded by one of
admirable finish and perfect aptitude for its designed uses; and
now that its construction is no longer dependent upon the skill of
the workman alone, but upon machinery moving with the precision of
clockwork, the fitting of the various parts is accomplished with
the greatest ease and certainty. The sale being thus extended, the
price has considerably diminished--the monopoly enjoyed by one or two
makers no longer exists; and there are few of a mechanical turn of
mind who cannot now provide themselves with a lathe suited to their
requirements.
Nevertheless, the adepts in the art of turning are by no means so
numerous as might be expected, and, among amateurs especially, it is
rare to find work executed in first-rate style by simple hand tools
requiring skill and practice in their use, so that it not unfrequently
happens that a workman who can turn out exquisite specimens of ivory
carving and ornamental lathe work, is but a fourth-rate hand with the
gouge and chisel.
But however beautifully executed such ornamental work may be, the
_credit_ is rather due to the tool than the workman, and a
well turned box with accurately fitting cover may bespeak more skill
in handiwork than the above elaborately designed specimen.
Moreover the one requires lathe fittings, which are not always to be
had unless the purse is well filled, whereas the general mechanic
(amateur or professional) can provide the tools needed for the other;
hence we propose first of all to give some practical hints on plain
hand turning of wood and metal. The ordinary form of foot lathe is
well known and requires no special description, it is represented in
the frontispiece of this volume. There are, however, certain points
of detail in its construction, to which it is necessary to direct the
reader's attention.
First and foremost comes the mandrel, of which there are several
patterns, according to the special purpose for which the lathe may be
intended.
Now of whatever form it may be made this is the essential part of
the lathe, and must run with the utmost truth in its bearings.
Imperfection here will be imparted to all work executed upon it, and
accuracy in this part alone will make up for any slight defects that
may occur in less important parts of the machine.
For ordinary work in wood alone or in brass the best form is
represented in Fig. 1.
[Illustration: FIG. 1.]
[Illustration: FIG. 3.]
[Illustration: FIG. 2.]
The part _a, b_, should be cylindrical, with a feather let in to fit
a slot in the pulley shown in Fig. 2. This pulley, whether of hard
wood or metal, is thus slipped on the mandrel as far as the collar
_d, d_, and a nut _e_, screwed up tightly at the back of it, fixes
it securely in its place, from which it may be moved if requisite
and replaced without fear of being out of truth. This cannot be done
if the mandrel is squared at _a, b_, and the pulley driven on with a
hammer, as commonly done by inferior workmen. The part _c_, is made
conical, to fit a hardened steel collar of similar shape. The angle
of this conical part is of some importance, as if it is too small the
mandrel is apt to jam and stick tight in its bearings. 35° will be
found to work well. With regard to the length of this conical part,
opinions differ considerably, but it must be remembered that friction
is independent of the _extent_ of the bearing surfaces and depends
on the force with which they are pressed together (in the present
case it depends on the tension of the lathe cord and the weight of
the material to be turned), so that a tolerably wide margin may be
allowed in this matter. Practically the question is decided by the
thickness of the casting of the poppet head, _which_ is regulated by
the required strength and size of the lathe. The collar is sometimes
of hardened steel, sometimes of brass. The latter would theoretically
cause less friction than the former, but practically nothing can beat
a well finished collar of hard steel. Collars of this material made by
the original Holtzapffel two generations back are now as good as ever,
perhaps even better. The centre, which screws up against the left-hand
end of the mandrel, should be of the form shown in Fig. 3--a plain
cylinder with a screw cut at each end to receive clamping nuts. The
central part is rather larger than the screwed parts, and passes truly
through the poppet head. This form is much better than a simple screw
with points, as the latter is not likely to keep the line of centres
in being screwed up into its place.
It will be found of great convenience to have the screw on the nose
of the mandrel (and indeed _all_ screws about the lathe) of standard
Whit worth pitch, as taps for the chucks are thus readily obtained,
and nuts and screws of the various sizes may be also procured to
remedy breakages and losses. Upon this subject, however, we shall have
occasion to treat more fully when we pass from the description of the
lathe itself to the work that is to be accomplished by its aid.
The only form of back poppet that need be particularised is that made
with cylinder and leading screw. The simple pointed screw passing
through the lathe head tapped to receive it, not only requires
no special description, but it is only calculated for lathes of
the commonest design, as it is seldom that the line of centres is
accurately maintained by the point at every part of the revolution
of the screw. Moreover, the latter soon works loose in the poppet,
and for anything like accurate work becomes speedily useless. The
cylinder and _pushing_ screw is indeed far superior to the form just
alluded to, and where cheapness is an object it has its advantages
over the first-named and best form. It is represented in Fig. 4. The
cylindrical part is shown at B, and may have at one end the usual
point, and at the other a small conical hole or hollow centre. It may
then be reversed in its bearings at pleasure, or other cylinders with
different shaped ends can be substituted, as may be found convenient.
Of course the pushing screw A is for the purpose of advancing the
cylinder, which is clamped by the small screw at C. The cylinder and
leading screw are shown in detail in Fig. 5, which is the poppet
head bored throughout to receive the spindle or cylinder A. At the
right hand this bore is enlarged to form a recess, B, to receive
the head of the leading screw, C. This screw is generally made with
a left-handed thread, so as to withdraw the back centre when turned
from right to left. The spindle A, A is bored, and a left-handed female
thread is cut from end to end--this however is turned off at the place
destined to receive the movable point or centre, and a hole slightly
tapering is cut, or if preferred a cylindrical hole is made and tapped
for the same purpose. The spindle has also a slot cut from end to end,
into which a screw enters from the poppet, preventing the spindle from
turning round while the internal screw is revolving by means of the
small wheel and handle fixed to its right hand end. The spindle is
now put in its place, the screw inserted and turned till the head or
flange, C, rests in the recess before mentioned--a flat plate, F, is
then attached to the back of the poppet by three or four screws, the
head of the leading screw passing through its centre; the small wheel
is then attached and the whole is complete.
[Illustration: FIG. 4.]
[Illustration: FIG. 5.]
It is evident that by turning the wheel the internal screw is put
in revolution, and as it is prevented by its flange from assuming
any motion in the direction of its length, the movable cylinder will
instead be withdrawn or thrust forward.
This form of poppet is the best that can be adopted and is of general
use in all first-class lathes. In addition to the movable point _g_, a
flange similar to H should be fitted. This will be found of great use
when the lathe is used for drilling, the piece of work resting against
it, while the pressure is regulated by the leading screw.
There are, in addition to the flange and pointed centre, other pieces
of apparatus that can be substituted, as occasion may require, and
these will be hereafter described in this series. With regard to the
common rest for hand turning a lengthened description is unnecessary.
The T or tee should for wood turning be of the form shown in Fig. 6 at
A. It is often made as B, which is a very inconvenient pattern, as the
cross piece on which the tool rests cannot be advanced sufficiently
close to the work if the latter exceeds a diameter of two or three
inches. For metal turning the top of the rest should be flat, and
about one inch broad, as the heel of the hook tools used for turning
iron must be able to take a firm bearing upon its surface. Sometimes
a plate of brass is riveted on the flat top, as the tool takes a
firmer hold on this metal, and when the latter becomes defaced and
channelled it can be renewed without the cost of a new casting in
iron. The turner should be provided with two or three tees for metal
and for wood,--one may be long enough to have two legs and require
two sockets, as shown at C. This is convenient in turning long pieces
of wood,--a very short tee, not more than an inch in length, should
also be provided, and if one tee is specially kept with a very level
and smooth edge, it will be found of great advantage in chasing
screws--indeed the latter work can hardly be managed at all if the top
of the rest is damaged and uneven. The next part requiring description
is the boring collar, without which even a hand turning lathe can
hardly be considered complete. This boring collar is intended so to
support one end of the work, instead of its being held by the back
centre, as to enable the workman to get at the end of it for the
purpose of drilling it. Suppose for instance the work in hand is a
tool handle, and that it is so far finished as only to require the
hole for the reception of the tang of the tool. If this is bored by
hand with a gimlet, it is seldom that the hole will be truly in the
axis of the piece, but when this is done in the lathe by the help
of the boring collar the bore will be truly central, and the tool
when in place will fall in the same line with the handle. This will
conduce to the correctness of the work in hand more than the amateur
or other workman might suppose, and a row of tools thus truly handled
and in good condition generally bespeaks an efficient and careful
artisan. There are several plans for boring collar of nearly equal
efficiency, and we shall describe one or two of the most common, and
also one invented by the author, and which, if carefully made, is of
great service. Fig. 7 represents a poppet head, B, which is but half
the height of the other poppets of the lathe--a side view of this is
shown at B, Fig. 8. Near the top of this poppet is a hole through
which passes a bolt C, by which and its nut the circular plate A can
be securely clamped in any desired position, as it revolves freely on
the bolt as a centre pin. This plate is bored with a series of conical
holes, which are so arranged that their respective centres will be in
a line with the centres of the mandrel when any one of them is brought
into a position corresponding with the line _c, c_. The hole thus
brought into position for use (having been selected according to the
size of the work to be bored), takes the place of the back centre;
the end of the work rests in the cone, which is greased or soaped to
reduce friction, and the rest being fixed at the other side of the
boring collar, the drill can be readily used, and the bore afterwards
enlarged if necessary with any convenient tool. This boring collar is
generally made of iron, but a substitute of hard wood will frequently
serve the purpose, and can be made by the amateur, who may be unable
to obtain one of more durable material. If made of wood the best
unguent will be soap or black lead, such as is used for grates, or a
mixture of the two. This black lead or plumbago (it has no lead in its
composition) will always be found serviceable where wood works upon
wood, and also to give a smooth surface to wooden patterns for casting.
[Illustration: FIG. 6.]
[Illustration: FIG. 7.]
[Illustration: FIG. 8.]
Where cost is an object, a simple substitute for the boring collar
is frequently made by the ordinary workman by a piece of board one
inch thick, shaped like Fig. 9, with a single hole of the size most
generally required; and the work is then fitted to the boring collar,
instead of the latter to the work. In turning tool handles, for
instance, where a few dozen are required all of the same size, or
nearly so, a device of this kind, which can be made in a few minutes,
is sufficiently effective. This form has been modified in two ways,
and either will be found convenient. In the first, the conical hole
is made of the largest size likely to be required, a set of boxwood
plugs are then turned to fit this hole and are themselves bored in a
similar way to suit various sizes of work. The form of these plugs is
shown in Fig. 10, which is a side sectional view, and at B, where the
same is shown in perspective. Two small screws or pins _b, c_, Fig.
10, fitting into the holes _a, a_, Fig. 9, prevent these flange-shaped
plugs from turning round in the board as the work revolves. The
pattern of A, Fig. 9, may be varied, and is better made of hard wood,
and of a form which will afford a good bearing upon the lathe bed.
[Illustration: FIG. 9.]
[Illustration: FIG. 10.]
The second modification is more difficult to make, but equally
effective. It is shown complete in Fig. 11. This form, arranged by
the writer, has many advantages over the two last-named, and is very
serviceable. A is the poppet, of the full height of the ordinary
lathe heads, or a couple of inches higher. B, the slide forming the
support of the piece to be bored. The form of the poppet without this
attachment is shown in Fig. 12. If for nice work it should be made
of metal and the face of it planed, but for general purposes hard
wood will suffice. _b, b_, Fig. 11, are two pieces of brass forming a
groove or guide in which a slide B, with dovetailed edges is fitted
to work. This slide is bored, like the ordinary collar, with conical
holes of different sizes, and should be made of metal and planed on
back and edges. Over each hole is a mark, and this is to be brought to
a similar mark on the face of the poppet. The plate is then clamped
in position by a screw at the back of the poppet. One or more of such
slides may be fitted at pleasure, and in case of wear or damage these
are the only parts requiring to be renewed.
[Illustration: FIG. 11.]
[Illustration: FIG. 12.]
It is a good plan to arrange a socket and tee of a rest as _b, c_,
Fig. 13, at the back of this boring collar, especially as the position
of the tool will be always the same, so that the rest may be a
permanent part of the poppet. There is sometimes a difficulty with the
ordinary form of boring collar in advancing the rest T sufficiently
near the work (the foot of the poppet, and that of the rest preventing
it, by coming in contact.) There is another modification of boring
collar, forming at the same time a guide for the drill, which in
slender work, where the tool is long and fine, becomes almost a matter
of necessity.
[Illustration: FIG. 13.]
This consists in making such a guide cone as mentioned and shown
in Fig. 10, B, but with a continuation containing a smaller hole
for the drill, as Fig. 14. Both this and the other shorter cones
above-mentioned may be made to screw into the poppet A, Fig. 9,
instead of being kept in place by the pins at _a, a_, of that figure.
In that case however the hole in the poppet must be cylindrical and
only used as a support for the cones themselves. In addition to
the use of these boring collars already alluded to, they serve for
the purpose of turning up the points of screws like those of lathe
centres. These are first formed between centres with carrier chuck,
the back poppet is then removed and the extreme point fitted through
one of the holes of the boring collar and the marks of the centre
turned off.
[Illustration: FIG. 14.]
Another useful adjunct to the lathe is the back rest for supporting
long and slender articles, which would otherwise bend under the
pressure of the tool. The ordinary and simplest form is shown in Fig.
15, and this is of general use with brush handle makers and others
whose work is confined to a few sizes and shapes only. A better form
is shown in Fig. 16. A support of wood or metal shaped like A is
clamped to the lathe bed. Through the upper part the slide B passes
and is wedged up so as to support the work--or the socket of a lathe
rest may be arranged to take the upright part A, which must then be
rounded, as shown at C.
[Illustration: FIG. 15.]
[Illustration: FIG. 16.]
A modification of the latter, communicated to the _English Mechanic_,
is shown in Fig. 16A. Its construction and mode of application is
sufficiently evident without a detailed description. Fig. 16B is
another form made in metal. It consists of two similar plates with a
triangular opening A, through which the work is passed, and which has
an oval slot D, by which the apparatus is secured to the short poppet
of the boring collar. Between the two plates slides a third, partly
visible at C, which can be clamped by a screw at B, this screw also
serving as a stud by which the plate may be moved. The work is allowed
to take up its own bearing in the triangular opening as it revolves in
the lathe. The clamping screw of the poppet is then secured, and the
centering thus made certain. The plate C is then made to descend so as
to touch the work, and clamped in that position. This is a very good
central support for long slender articles.
[Illustration: FIG. 16A.]
[Illustration: FIG. 16B.]
There is a plan practised by German turners by which the back rest
is in a measure superseded, and which may be mentioned here. It is
simply the peculiar method of using the left hand. This is placed on
the piece to be turned so that the fingers partly encircle the work
while the thumb rests in the hollow of the gouge, or upon the end of
the tool. The fingers thus form a back rest and keep the work pressed
against the cutting edge, which is further steadied by the thumb. As
the tool traverses the work the left-hand accompanies it, and with
a little practice a ramrod or similar long and slender article may
be readily and accurately turned. This position is shown in Fig. 17,
and though the novice will find it difficult to work thus, it is well
worth the trouble of mastering, as the method once acquired will be
found of very great service.
[Illustration: FIG. 17.]
We have now described more or less in detail the principal parts of
the lathe as adapted for hand turning. Before we dismiss this part
of the subject, however, it will be necessary to say a few words
respecting the bed and lower fittings, the flywheel, treadle, and
their adjuncts.
Beyond question the iron bed, planed as it now is at a moderate price,
by machinery, is the best that can be adopted, especially if it is
intended eventually to fit up the simple tool with slide rest and
superior apparatus. Nevertheless, the pocket must in this case also
frequently decide the question of material. If wood is preferred by
necessity or otherwise, it should be _hard_ wood, beech, or Spanish
mahogany, unless it is proposed to plate the surface with iron. This
latter plan costs little and, besides stiffening the bed, it prevents
the wear and tear caused by the constant shifting of the back poppet
and rest. A flat strip of iron one inch or an inch and a half wide
can be picked out from the stores of any village blacksmith straight
and level as it came from the rolls of the manufacturer. Selecting a
piece of the required length and breadth, the eighth of an inch thick
or rather more, the purchaser will have holes drilled and countersunk
at intervals of nine or ten inches, to receive 3/4-inch screws.
These strips will have to be laid upon the top of the bed, at its
inner edges; they need not be let in flush with the surface unless
appearance is studied.
They must then be screwed down firmly, and by means of a file worked
by both hands up and down their length (not across them) a good
surface may be readily obtained. If the iron is let into the bed this
filing will abrade the wood work, which is the reason why we prefer
screwing it on the surface. This method produces a very excellent and
durable lathe bed, and it will be free from much of the tremor which
is so disagreeable while working upon a lathe entirely of cast iron
unless the bed of the latter and the standards are more substantial
than is usual with small lathes.
The standards supporting the axle of the fly wheel and bed may in like
manner be of wood or iron. Even when the bed is of iron these may
be of hard wood, although it is customary to make them of the same
material as the bed. If of beech, oak, or mahogany, as in some of
Holtzapffel's best lathes with iron beds, the tremor before alluded to
will be considerably lessened. Iron is nevertheless very neat, and is
quite the fashion with the majority of makers, but is too often faulty
in respect of solidity.
The standards as a rule are too slight, an elegant pattern being
studied to the sacrifice of substance and weight, The bed and stand of
a lathe cannot be too strong and stiff.
Respecting this matter of stiffness and solidity we seldom find it
sufficiently considered, and, even with practical workmen, a defect in
this particular is more frequently acknowledged and put up with than
remedied, although the _comfort_ of a steady lathe is beyond question,
to say nothing of its superiority when good workmanship is studied
(as it always should be). The old French lathes made in the form of
a thick table with four stout legs, forming the bed and back-board,
are by no means to be despised as patterns; and instead of the usual
method of making but one standard at end of the bed, there can be no
question that two additional ones add considerably to the stability of
the machine.
The fly wheel should be sufficiently heavy and have three speed
grooves on the rim and two additional ones to produce a slow motion,
which is required for turning metal. The latter may be worked with
ease in this way when the article to be turned is small, but if
heavy work is likely to be encountered the back geared lathe, to be
hereafter described, must be substituted, and the slide rest will then
also replace the hand tools. The crank axle is generally supported by
two centre screws, the points being hardened, and also the ends of
the axles, which are accordingly made of steel, and the holes for the
centre screws neatly drilled and countersunk.
This is however not the most perfect method, and as we are speaking of
better class lathes, as well as those of more common and cheaper make,
we must by no means omit to speak of a very superior way of fitting
the crank axle. The latter must be turned at both ends, the wheel
bored and slipped on, and keyed in its place.
Two wheels of brass about two inches diameter, must then take the
place of the centre screws. These are called friction wheels, and they
must be placed sufficiently near each other to support the end of the
axle between them, as shown in Fig. 17B, _a_ and _b_. A pair of these
must be thus fitted to each standard, and after the axle is placed in
position a third may be placed above it to prevent the lathe cord from
lifting the axle out of place by its tension. The axle and friction
wheels will thus work together with an exquisitely smooth rolling
motion--there will be no tendency to thrust the lathe standards apart
as must result from tightening the ordinary centre screws, and the
friction of the axle on its bearings will be reduced to a minimum.
Any person acquainted with the use of the lathe may readily fit up
these friction wheels, and the time and trouble so expended will be
amply repaid by the superior ease with which the lathe can be used. We
may say the same of the chain and eccentric, which can replace with
similar advantage the crank and hook in ordinary use.
[Illustration: FIG. 17B.]
[Illustration: FIG. 18.]
For the latter the following arrangements are necessary. A is the
eccentric keyed to the crank axle, and may be either in the middle
of the same or, as in Muir's patent lathes, at one end outside the
standard. Around it passes the endless flat chain B (known as crank
chain). This also passes round a roller in the treadle shown at C.
This chain does not act as a mere link, but when the lathe is in
action it moves round and over the eccentric and treadle roller. The
motion of the whole is smooth and regular, and, what is almost as
important, _noiseless_. In Muir's and other lathes the crank chain
is used without the eccentric, being applied to the crank instead.
Perhaps there is not much to choose between the two, but no one who
has studied the eccentric and observed its exquisitely gentle and
smooth motion in an ordinary engine can have failed to be struck by
these valuable qualities. It must however be remembered that its throw
is half that of a crank of the same eccentricity and the latter will
have the advantage in power size for size.
In whatever position the lathe may be set up let the rise of the
treadle be moderate. It is exceedingly disagreeable to work at a lathe
where the rise of the foot board is so great as to bring the knee into
contact with the lathe bed, a consummation not infrequent in country
made ones.
This is only to be escaped by giving up a certain portion of power.
Let A, B, Fig. 19, be the line of the treadle when at rest; _c_,
the crank. To gain power we should let part A, E, be longer than E, B,
as in the sketch. But let this arrangement be made, and when the
crank is at its highest point, the line G, B, will show the position
of the treadle and foot board. Hence this kind of leverage is not
practicably available to any extent, and the length taken from foot
board to link may with advantage be even less than that from link to
the axle on which the treadle works. In lathes, of all machine tools,
it is essential that the workman should be able to stand easily, that
the movements of the leg and body should not be communicated to the
tool, the play of the treadle and such items of detail being of more
consequence than might at first sight appear, and any method tending
to diminish friction, vibration, and noise is well worth consideration
in planning this machine.
[Illustration: FIG. 19.]
We may now suppose the reader the happy possessor of a well made foot
lathe, long or short in bed, high or low in poppet, according to his
need, but, of whatever size, carefully made and firmly fixed in a
well-lighted place, and if possible on the basement floor--an upstairs
workshop is objectionable owing to the certain vibration of a boarded
floor. He will now require certain chucks and tools, many of the
former of which he will have to make for himself.