We now enter upon the actual work of the lathe, which should be
comparatively easy to understand after the foregoing observations.
Your raw material having been chopped or shaved into a rough cylindrical
form, you have to mount it in the lathe. I may suppose it a piece of
beech for a tool-handle. If you have the cross-chuck, you should use it;
if not, you may use the prong instead. In either case, centre the wood as
truly as you can, so that, when the rest is fixed near it, the piece may
not be much farther from it, as it revolves, in one place than another.
Mind and screw down the back poppit tightly upon the lathe-bed, and also
the rest, putting the latter as near the work as you can without touching
it. Now set the lathe in motion,—this is tolerably easy, but to keep it
in motion will probably not be easy at all. It is one of those operations
which require practice, because while your leg is at work upon the
treadle, your body must be firm and still, so that you feel yourself free
to use the tools without giving much attention to what your leg is doing.
After a while you will do this with perfect ease. The wood is, of course,
to rotate towards you, and the surface will come in contact with the
edge of the tool as the latter is _held tightly down on the rest_. Now,
this is, after all, the real difficulty, for every projection striking
the tool tends to jerk it off the rest, and this has to be resisted with
some force. There is, however, this advantage in hand-tools, viz., that
they may be held rigidly yet be allowed some slight play, according to
the peculiar exigencies of the work; and at first you will save the tool
by allowing it to yield slightly until the roughest part has been cut
away. Afterwards, there is to be no movement except that required to make
it follow the curves or level parts of the work. Do your best first to
produce a cylinder, _i.e._, a straight, even piece of wood, as long as
the required handle, and as large round as the largest part proposed to
be given it. It is the best plan at first to copy a well-shaped handle,
and to turn as many as you want of that size exactly to the same pattern.
This will give you such an amount of practice in copying form, as will
stand you in good stead in after days; for it is not easy at first to
turn even two things exactly to pattern and to _size_.
You must not expect to be able to run your tools along the work like a
professional or old hand at the lathe; you must do the best you can. Hold
the handle in the right hand, and with the left grasp both rest and tool
together, and you will hold it firmly. Then you _ought_ to run it along
right or left at the right speed and the right angle, but you will be
unable to do so yet;—never mind. Remember the _principle_ I have laid
down as to the position and angles of cutting tools, and trust to time
and perseverance to make you a good workman.
The gouge is the easiest and best tool to use at first; and you can do a
fair amount of _smooth_ work with it if you know how, although smoothing
and levelling is the special work of the chisel. The gouge, however, is
used for all sorts of curves and hollows, and though the actual point
will only turn a groove if held still, the _side_ of the cutting part
will, if the tool is steadily advanced, turn very fair surfaces indeed.
I strongly advise practice with this tool before attempting to use any
other. Your early work is of little importance, and you may make up your
mind to cut several pieces into shavings and chips without very grand
success, even though you use a chisel; so I repeat, stick to the gouge
only for some time, until you can use it towards left or right, and with
either hand grasping the handle.
With the chisel, far more care is required than with the last named.
It is altogether a more difficult tool to use. Its position may be
described as follows, but practice alone will render its use easy. Lay
it first flat on the rest as you would the gouge, and let it point
upwards at a similar angle, until it also is in the position the gouge
would take, ready to cut the piece of wood in the lathe, already turned
to the cylindrical form by the latter tool. You will find one point or
angle of the edge, the sharpest, reach the wood before the other, and
will see at once that this would be liable to catch in, if the lathe
were in motion—and so it would. I shall suppose that this sharpest angle
is on the right-hand side as it lies flat on the rest, and against the
wood. Raise that angle so that the tool lies a little edgewise on the
rest instead of quite flat, when the angle of the tool that is highest
on the wood will be also raised off it; the lower angle and remainder of
the edge still being in contact with it. This is its proper position,
with the upper angle out of contact with the work. You may turn it over
so that the keenest angle is the lower one, but then you must raise the
other, which is now the upper one, for under no circumstances must the
one that is uppermost touch the wood. The chisel, therefore, never lies
flat on the rest or on the work, but always slightly raised to clear the
upper point, and in this position you have to keep it, making it descend
into hollows, and rise over mouldings, and cut level places, almost
without stopping an instant; and for wood, especially soft wood, the
lathe is always itself to be run at a very high speed, by putting the
cord on the largest part of the fly-wheel and smallest part of the pulley.
To return to the supposed tool-handle. Having turned a cylinder, begin
at the ferule, which you must cut off a brass or iron tube, or, which is
easier, buy by the dozen or by the pound ready cut. You will want them
three-quarters of an inch for your largest tools, and about three-eighths
for the smallest, with some of half an inch, and you can then bore your
tool-rack exactly true with centrebits of these sizes. Turn the place
down for the ferule, and take care that you make a tight fit. Gauge with
the callipers first of all, and turn almost to size, then try it on once
or twice until it fits exactly.
If you use the cross-chuck, you have this one great advantage—you can
take out your work to put on the ferule, and replace it exactly as it was
before, and it will continue to run true. As, however, the piece in the
present case is but partially turned, it can be replaced with sufficient
accuracy upon the prong-chuck, especially if you mark the side of the
chuck, and of the piece of wood, and take care to replace them in the
same relative position. You must now try with gouge and chisel to imitate
the pattern handle, remembering always to work downwards from right and
left into the various hollows—(you cannot cut the fibres neatly if you
try to go up-hill); and where the two cuts meet in the hollows, you must
do your best not to leave the least ridge or mark. You will be sure to
need a little glasscloth to finish off your work, but do without it as
much as possible, because it spoils the shape of mouldings, rubbing off
the sharp angles, which in many cases add beauty to the work. If the
piece of wood is longer than necessary, cut it off with the chisel. In
any case, you must cut off a piece at the chuck end; and this being the
end of the handle which you will hold in your hand, the ferule being at
the end next to the back poppit, you will cut it off neatly with the
chisel in finishing it to the required shape.
You would hardly suppose it possible to turn off the end of a piece
squarely and accurately with the gouge, but it is a good tool for the
purpose. You must lay it on its side upon the rest, so that its back or
bevel rests flat against the end of the piece from which the superfluous
wood is to be taken; the edge or point of the tool is then allowed to cut
the work by a slight movement of the handle. You can only do it in this
way, with the bevel against the piece from which the cut is to be taken.
Turned over to its usual position, it will hitch in and spoil the work
in a moment. In the same way you can face up a bread-platter or similar
flat work; but such articles as these are not mounted between centres,
but screwed upon the taper screw-chuck or the flat plate with the
screw-holes, so that you can get to the face of them. At first, however,
until the work gets tolerably level, you may bring up the back-centre,
which will prevent the taper screw of the chuck from being accidentally
bent; and when all the rough part is cut away, and the rim turned down,
you can remove the back-centre to finish the facing up. In this work,
however, the back and face do not need much turning, because the platter
is turned from plank wood, planed up truly on each side, and cut roughly
into the form of a circle. If accurately planed, it will run true at
once, and the small amount of facing may be done with the gouge held as
directed. Afterwards it may be necessary to take a light _scrape_ with a
_carpenter’s_ chisel, which answers well for this. Then finish up with
glass or sand paper. Take care to make a neat moulding to the edge, which
will be about an inch thick, and will therefore look very heavy unless
turned off so as to thin it down. A platter is a very good and useful
work for a beginner.
In turning a platter you will certainly learn one lesson in mechanics.
You will find that it is very hard work to turn anything that is larger
than the pulley of your lathe, and you will only be able to take a very
light cut. Probably you will find it the easiest plan to set the lathe
in rapid movement, and apply the turning-tool only for an instant, and
then to remove it until the work has recovered its impetus, thus cutting
it, as it were, by repeated brief applications of the tool, instead of by
one continuous cut. I do not mean that the tool is to be removed from
the rest, but only eased off for a second from the work. If the latter is
very large, and the pulley on the mandrel much less in size, you can only
work in this way, finishing with a very light cut. There is a tool for
the face of such flat works, called a broad. It is like a broad chisel
with the end turned up at right angles to the side, only the edge is a
bevelled one and thick. They work well in hands accustomed to them, but
the gouge and chisel are sufficient for your present need.
I shall sketch here (Fig. 49) one or two articles not requiring to
be much hollowed out, which will help you to decide upon such work
as is suitable to a young mechanic desiring, by steady practice and
application, to become a proficient at the lathe, and as soft-wood
turning will teach you more than that in hard wood, I shall direct all
the following to be made of it by gouge and chisel alone.
[Illustration: Fig. 49.]
These examples are not given as specimens of the rich work which can be
done in the lathe, but as easy examples of elementary turning. No. 1 is a
stand for an urn or hot water jug, and a slight recess may be made in the
upper surface, in which a piece of cloth, or carpet, or oilcloth can be
glued, which will make a neat finish. No. 2 is a bread-platter, showing
how a little neat moulding takes away the clumsy appearance of the thick
board necessary for this purpose. No. 3 is a candlestick. The lower part
or stand is to be turned from a separate piece of thick board screwed
upon the taper-screw chuck. While it is in the lathe, the hole must be
made in the centre (or marked, if the piece is not very thick) by holding
a pointed tool a little on one side of the centre, so as to describe a
circle of the requisite size. Into this will be fitted a tenon, fig. 3 B,
which is turned on the pedestal, and which is to be glued into its place.
By and by you will learn how to cut a screw upon such a tenon, which is a
far more satisfactory method of proceeding; at present glue will answer
just as well. You can make the upper part separate, forming the junction
at the line C (Fig. 49, No. 3), if you prefer it, or if your wood is not
long enough; but as you will not hollow out the top, you may as well let
it be cut out of one piece with the pedestal. Turn the top quite level,
drive in a piece of stout wire, and point the end of it. Cut out a round
piece of tin to fit, and make a hole in the middle of it to let the wire
through; drop it over the point, and let it rest on the candlestick; a
wax candle can be spiked upon the wire, and will stand firm.
Figs. 7 and 8 are drawings of tool-handles. These are the best shape to
grasp in the hand, and they look neat in the tool-rack. Tool-handles
with a number of mouldings, are not only absurd, but are uncomfortable
to hold, and not at all suited to their intended purpose. 9 and 10 are
other forms of mouldings, and are given merely to show how angular and
rounded forms should be combined to produce a good effect. If these were
to be made in hard wood, they might be turned with beading and moulding
tools similar to those at A, B, C, D of this figure; such tools are
bevelled only on one side, and being held flat upon the rest, cut the
curves and hollows rapidly, and clean. Sometimes a number of these are
arranged side by side, so as together to make up the outline of the
intended moulding, and being held in position by a handle designed for
the purpose, are presented all at once to the work as it revolves. In
other cases, a flat plate of steel is filed into shape, and bevelled to
form a compound moulding tool. Of course, such contrivances greatly help
the turner, especially if he has to turn a number of articles of exactly
the same pattern, such as the pawns of a set of chessmen, or a set of
draughtsmen; but none of these tools answer upon soft wood, because, as
already explained, tools which have to be held horizontally will cut and
tear up the fibres of all woods that are not very hard and compact in
grain.
Fig. 6 is a profile of a draughtsman, and fig. 6 B shows how they ought
to be made, but for this you cannot use soft wood, and had better make
them of box and ebony, or holly and ebony—(and, by and by, of black-wood
and ivory). A cylinder is first turned, then marked off as shown with
grooves cut by a parting-tool. The pieces are then separated with a fine
saw, and a chuck is hollowed out to fit them so that each can be readily
turned upon the face. The desired mouldings having been made on one side,
the disc is turned over in the chuck, and the other side operated upon in
the same manner.
It is quite _possible_, you must understand, to cut these out of soft
wood, even pine or deal. We often see boxes of toys, children’s wooden
plates and cups, turned very neatly of this material; but it is not worth
while to use it if you can obtain boxwood. Moreover, box can be stained
black to imitate ebony, and is very often made to serve instead of it.
Figs. 4 and 5 are ring-stands for the toilette-table—very useful presents
these to mothers, sisters, and, last but not least, lady cousins, and
other young ladies too, perhaps, who are not cousins. These can be made
in a variety of ways, and give great scope for the exercise of your
powers of design. The first is a simple pedestal on a stand, turned quite
smooth in an elegant and simple curve. The stand is also made without
elaborate mouldings, giving altogether a chaste and elegant appearance
to the design. The extremity is tipped with ivory, and an ivory ring
surrounds the bottom of the pedestal. If this is made in plain deal,
and thoroughly well finished and varnished, it will look very well. The
nicest soft English wood, however, for this is certainly yew, some of
which is beautifully fine in grain; and as it will take an excellent
polish, it always looks well; moreover, it can be turned entirely with
gouge and chisel.
This ring-stand will be made in two parts; the pedestal being separately
turned at one end, a tenon will have to be made as in the case of the
candlestick, and just above it the wood is to be turned off a little
as if you were going to make a larger tenon. Over this a ring of ivory
may be slipped and glued on, and the two can then be turned together.
A carpenter’s chisel will do for the ivory, which will be scraped into
form by it. It may be polished with a little chalk on a moist rag or
flannel. You can buy odds and ends of ivory from the turners in rings and
solid pieces, which will come in for all sorts of decorations, and you
should save all old handles of knives, tooth-brushes, and such like, for
a similar purpose. Both ivory and bone smell very disagreeably when in
process of being turned. To tip such articles with ivory, you can drill a
small hole in the top of the pedestal with great care, and fit the ivory
after being turned into it; or you can, if the work is larger, bore the
ivory and slip it on the wood;—much depends upon the size and nature of
the work.
The second ring-stand is of rather more elaborate construction. The
baskets are made of little turned pedestals fitted into a round piece of
wood to form the bottom, and into a ring which makes the rim. Baskets of
this form (even apart from the ring-stand) are very neat and useful.
It is very easy to turn rings of any size. Mount a piece of board in the
lathe on the taper screw chuck—it need not even be cut to a round form;
then determine the size of the proposed ring, and, holding a parting-tool
upon the rest turned round to face the work, mark two circles, and deepen
the cuts, until the ring falls off. Take care that the outer one is cut
through first. The ring thus cut may be afterwards placed upon a cylinder
turned to fit it, and finished upon the outside, and then placed inside
a chuck of wood bored out to suit the work, and neatly rounded off upon
the interior surface. Of course, if you have to make rings of bone or
ivory which are already hollow, you can at once run a mandrel or spindle
of wood or metal through them and subject them to the various operations
required.
Mandrels, or tapered cylinders of brass or iron, fitted as chucks to the
mandrel of the lathe, are sold on purpose for this work, but a wooden
rod answers just as well, and costs nothing. Turn such a rod a little
tapering, and take care not to drive the work too far upon it, because,
although at first you can safely drive it on very tightly, if it is of
ivory or bone, you will frequently find your ring suddenly split and
open when its thickness has been reduced to the required standard. If a
number of equal rings are required, it is the best plan to turn a hollow
cylinder and then saw off the rings as you are directed to saw off the
draughtsmen. They will, of course, have to be finished in a chuck.
If you look round any fancy warehouse in which Swiss carvings are sold,
you will see how beautifully soft white pine can be worked in the lathe
by keen tools and clever hands. In Tunbridge, too, many thousands of
soft-wood articles are manufactured yearly, some plain and merely
varnished, and some curiously inlaid with coloured woods, so that you
need not despise such materials as willow and sycamore and the various
pine woods, which are all capable of being made into pretty articles of
one kind or another. The varnish, however, for these is such as to coat
them with a glassy layer which does not sink into the wood. Common rosin
dissolved in turpentine or in linseed oil, kept on the hob so as to get
warm, answers well for these deal articles, and is extensively used where
the slight tinge of yellow is not considered important. There are many
other much paler varnishes for works of greater value, or where the white
wood is to be carefully preserved. Any of these can be had at oil and
colour shops.
[Illustration: Fig. 50.]
You will certainly find a difficulty in turning all exactly alike the
little pillars of these baskets. You should turn several at once out of
the same piece, separating them afterwards. Thus your pattern will always
be close to the half-executed copy, which will somewhat assist you. Do
your best in this respect, but be specially careful, at any rate, to
make all exactly the same length. One pillar is shown separate, but you
can design a pattern for yourself.
Begin by turning a long cylinder; then set off the respective lengths of
the pillars. Turn one complete as a pattern, and set the callipers to
the largest part of it. Then go to work upon a second, using callipers
freely at all parts of it. As these pillars will all be slender, you will
be in great danger of breaking them; therefore use your tools lightly,
taking only a very slight cut. But with all your care you will find it
difficult to turn a row of more than two or three of the size wanted for
such little baskets. I shall therefore show you how to make a support to
fit at the back of the bar you are at work upon to support it against the
pressure of the tool.
Fig. 50 gives a representation of one or two such supports, which are
often required in turning. The first is the most simple, and is the one
most generally in use, because easy to make and to apply, and it answers
tolerably well. A is merely a piece of wood, about three-quarters of an
inch thick, cut as shown. This is stood up between the lathe-beds, like
C, and fastened with a wedge before and behind. It allows the work in the
lathe to revolve in the notch which is cut in it, as is evident from the
drawing. One, two, or more such may be used if necessary. They must be
carefully adjusted, so as not to bend the piece which is to be turned,
and which is to be just supported, but no more. Where the _back-stay_,
as this contrivance is called, comes in contact with the work, the latter
is to be left of the size it was when this was adjusted to it as long as
possible. It must then be shifted a little, and that part which formerly
rested against it finished.
B is another simple form of back-stay, capable of nicer adjustment. The
foot is that of a common rest, but if you have not a spare one, any
wooden support is quite as good. Into this fits a turned part of the
upright _x y_,—the upper part, _y_, of this being planed flat. Neither
should be of deal; ash or elm is preferable. Thus the part _x y_ can be
raised and lowered at pleasure in the rest-socket. The top part is made
of a half-inch board, about 2 or 2½ inches wide; a slit is cut in it,
and it is fastened to _x y_ by a short bolt and nut. Thus it is easy to
raise and lower the end of this part, and to put it nearer to, or farther
from, the work in the lathe, against which it can be adjusted with great
nicety. Although there are several forms of back-stay, of more or less
complicated construction, I know of none more generally serviceable than
this last, which the young mechanic can make for himself. The notch
should be lubricated with soap, or, if the blackness is not of importance
(as when this part, which rotates in the notch, has finally to be cut
away), with a mixture of soap and blacklead. This, remember, is always to
be applied to wooden surfaces that are to work easily upon each other.
It will sometimes happen that you require to bore a hole through a long
piece of wood, as would be the case in making a wooden pipe, flute,
bodkin-case, and many similar articles. To hold these in a chuck only
would be often impossible, because the hole in the chuck would have to be
as deep at least as half the length of the piece to be bored.
For this kind of work, therefore, and for turning up a point on the
end of a cylinder of iron or steel, like that of your back poppit,
the following contrivance is used, which is called a boring-collar or
cone-plate. It is represented in Fig. 50, D and E. This consists of a
circular plate of metal, three-quarters of an inch thick, turning upon
a large screw or pivot at its centre, by which pivot it is attached to
a short poppit head, fitting between the bearers of the lathe as usual.
There are six or eight conical holes bored round the circular plate, each
of a different size; and these are so arranged as to height, or distance
from the centre, that the top one (being in a perpendicular line passing
through its centre and that of the bolt) is exactly as high as the axis
of the mandrel. Thus, if it is clamped in that position, with the largest
side of the conical holes next the mandrel, a piece of wood might be held
at one end in a chuck, while the other might rest in such hole as was
best suited to its size, not actually passing through it, but resting
in the inside of the conical hole, in which it would rotate almost as
freely and as truly as if it were supported by the ordinary point of the
back poppit.
Sometimes it may be preferred to allow the end of such a piece of work to
project through the cone-plate, a collar being turned on it to prevent it
from going too far. A tool-handle, for instance, of the pattern before
given, may be beautifully bored in the lathe by allowing the ferule
to rotate in one of the holes of the cone-plate, the shoulder behind
preventing it from going too far. The rest is brought round in front of
the end of the handle, and a hole bored by a drill for wood; or, the
point of a drill is brought against it, while the other end (having had a
slight hole made by a centre-punch for the purpose) is allowed to centre
itself on the point of the back poppit. The screw of the latter is then
advanced, and the drill being prevented from itself revolving either by
being grasped by the hand or a vice, a beautifully straight and even hole
is rapidly made.
Fig. 50, F, shows the position of the various pieces. The drill is here
kept from rotating by a small spanner, the handle of which comes against
the bed of the lathe. A great deal of work, both in wood and metal, is
always drilled in this way.
For wood, a small nose-bit, or auger-bit, or one of the American
twist-drills, can be used, and this may be succeeded by a larger, until
the hole will allow of the introduction of a finishing-tool of some
kind, held in the hand. Of course the latter is not necessary in boring
out handles for the tang of a tool, but only in turning boxes for
pencils, needles, or other articles, which require to be neatly finished
inside as well as out; all these are to be bored before the work is cut
free from the superfluous wood out of which it was turned. You can even
use the cross-chuck for this work.
It matters little, when using the cone-plate, whether you finish
the turning of the outside before or after the boring is done. Very
generally the box or other article is bored first, quite in its rough
state, except that a short piece is turned down to fit into a hole of
the cone-plate; and, keeping the latter in its place all the while, the
wood is turned down and polished before removing it from the lathe.
Sometimes, especially with metal, which is in no danger of splitting, the
cone-plate is removed as soon as the hole has been made and replaced by
the back-centre, the point of which, entering the hole, retains the work
in its place while the outside is being fashioned. This of course insures
the exterior surface being exactly concentric with the inside, which is
often absolutely necessary in parts of machinery; but if wooden articles
are finished in this way, there is great danger of their being split by
the pressure of the back-centre as the work grows thinner and thinner
under the action of the tools. Moreover, it must be remembered that the
back-centre, being itself of a conical form, will injure the form of the
hole in metal by making it wider at the mouth if used in this way, and
sometimes this may be of importance.
There is a fault in the cone-plate which boys will understand, and men,
too, I imagine. _It costs money!_ Therefore I shall now show you how
to make a substitute, which will cost something under a shilling, if
you do not mind a little trouble; but, if you do, you will never make a
good workman, nor will you be good for much, I fear, in any way! A metal
cone-plate for a 5-inch lathe costs £2 at least.
I shall suppose you want a cone-plate in which to bore your tool-handles,
for it is not easy to do this with a gimlet, so that the tools, when
inserted, shall stand straight in their handles. If you have a 5-inch
centre lathe, _i.e._, a lathe in which the central line or axis of the
mandrel is 5 inches from the lathe-bed (in which case you can turn
anything nearly 10 inches in diameter), cut out of a piece of beech, 3
inches thick, a short poppit 3½ inches high, of some such shape as seen
in the fig. G; and in the lower part (which must be cut to fit between
the lathe-bearers, and must be made square at the sides and true, so
that the whole will stand squarely across the lathe-bed), either cut a
mortice, _a_, for a wedge, or bore a hole for a screw, which must have
a plate and nut to fasten under the bed like other poppits. Near the
top, and exactly in the centre, bore a hole to receive the bolt K,
similar to that in the metal cone-plate already described, and which
will be tightened by a nut at the back. This supplies the place of the
short iron poppit, and now you have to contrive something to replace the
circular plate of holes. Cut two or three strips of any tolerably hard
wood, H (beech will answer very well), 6 inches long, half an inch thick,
and 2 inches wide. Cut in these a slot and a round hole, which must be
carefully made with a centrebit. This hole is to be for one of those in
the usual round plate, so be careful in making it. Work thus: Plane up
the piece from wood rather more than the half inch required; draw a line
exactly down the middle of it on both sides _e_, _f_; choose a centrebit
of the size you require; put the point upon this line, about 1½ inches
or more, according to the size of the required hole, and bore steadily a
little way into the wood. Then turn it over, measure carefully so as to
get the precise spot right, and finish from that side. If the centrebit
is sharp, and the wood sound, you will now have a neat round hole. Let
the slot be also cut from both sides of the piece of wood with a sharp
chisel, taking care that the centre of it agrees with the line that you
made for a guide.
Three or four of these should be made, each with a different sized hole,
or more if required; but you can add new ones at any time. The bolt, K,
is to be made with a large head flat on the under side, and the upper
part, above the screw, is to be square for three-eighths of an inch, and
the slot in the pieces of wood must just fit this squared part. Now, as
this is three-eighths only, and the thickness of the wood is four-eighths
or half an inch, it is plain that the nut will draw, and the head of the
screw clamp this tightly. You can, if you like, however, make the hole
in the poppit square also, and then let the squared part of the screw be
long enough to reach _almost_ entirely through both pieces. Then slip
a washer (an iron plate with a hole in it like L) over the end of the
screw, and fix all with the nut. Thus you have a boring collar with _one_
hole, and this you can raise or lower the length of the slot so as to get
it exactly the right height, and when it is so arranged, one turn of the
nut at the back will fix it.
This you will find a very simple form of boring-collar, easy to make, and
of practical use. If you really take all the care you can, and follow
the directions I have given, I do not see how you can possibly fail in
constructing one. You should have a sliding-plate with a hole for each
size of tool-handle ferule used, as you will frequently be making these.
HOLLOWING OUT WORK.
As I have spoken of boring, I will go on to treat now of the general
practice of hollowing out chucks and boxes, and such like. If this is to
be done in soft wood, such as willow, no tool will answer so well as the
hook-tools, of which I have given drawings. But these are very difficult
indeed to use, owing to their tendency to catch in, or take suddenly a
deeper cut than was intended. Nothing but practice will teach exactly how
to use these tools; but then, when the difficulty of so doing is once
mastered, nothing can be more rapid or more satisfactory than the work
which they will do. Small bowls are hollowed almost instantaneously by
their means in skilled hands; whereas, with other tools, it becomes not
only a tedious job, but if it is done at all, it is but roughly, the wood
having to be rather scraped out than cut. Using, however, the back of the
gouge as explained before, in the directions given for squaring up the
end of a cylinder with this tool, it is possible to hollow out soft wood
with it, but not very satisfactorily. In any case, other tools (generally
a carpenter’s chisel) must be used to work into the angle which neither
the gouge nor hook-tool can, of course, reach. Hence it is generally so
much easier to cut out boxes and such like articles in box or _hard_
wood, that this is nearly always used by amateurs.
The ordinary way to turn a box is as follows:—Prepare the wood as usual,
turning it cylindrical, using any chuck you please for this work; cut off
with the parting-tool rather more than the box and its cover together
will require, and drive the piece thus separated into a cup-chuck. [You
may, if you prefer it, screw upon the nose of the mandrel, or upon the
taper screw-chuck, the rough piece of the proper length, instead of first
turning a cylinder to cut from. If you have several boxes to make of one
size, the cylinder method is to be preferred.] Turn it up again quite
true, for although it was correct before you cut it off, it will not be
so now. Square up the end, and turning round the rest so as to stand
across the face of the wood, begin to hollow out _the cover_. Use either
the round end or pointed tool at first, and then a carpenter’s chisel or
flat tool to finish. Be very careful that the sides (I must call it by
this name, although a circle has not more sides than a plum-pudding) are
turned square to the bottom, or else, when the cover is put on, it will
perhaps fit just at the entry, and be quite loose when fairly on; or, it
may be that it will be easy at first, and when you press it on, it will
be tighter and become split,—a very common but unpleasant occurrence. Do
not, moreover, turn down these sides as thin as they will ultimately be;
because, after the box is hollowed and the cover fitted on, both will
have to be slightly turned together to finish them nicely. Moreover, you
may not wish your box to have plain sides, but may prefer to mould them
into a more elegant form. All these little questions have to be duly
considered in turning, for a mistake is often made, and the work spoiled,
for want of a little timely consideration.
The next point on which you have to be on your guard is this,—having
turned out the cover, you have to cut it off, not with a saw, but with
your parting-tool. Now, be sure to leave thickness enough for the top
of the cover; or, just as you think you have nearly severed the latter
from the rest of the piece of wood, you will see a beautiful little ring
tumble off,—sad relict of your box cover, which has come to an untimely
end.
The sliding square of the turner, of which I gave a description among
the list of tools, will always enable you to gauge both the depth to
which the work is hollowed out, and also the squareness of the inside
to the bottom. But if you have no turner’s square, you can easily gauge
the depth inside, and thus see how much is necessary to be allowed for
the thickness of the top. Keep the parting-tool edgewise on the rest,
which should be raised to such a height that, when this tool is laid
horizontally across it, it will point nearly to the centre of the work,
_i.e._, the axis of it. After the parting-tool has cut into the wood a
little way, widen the groove a little, and continue to give the tool a
little play right and left, unless its end is so much wider than its
blade generally that it will clear itself perfectly as it goes deeper and
deeper into cut. If it should bind, it is almost certain to break, for
it is a very thin tool; and it is better to waste a little more of your
material than to have to replace a spoiled tool.
I shall suppose that you have now succeeded in cutting off the cover;
pick it up and lay it near you. Directions are given generally to turn
down next the flange upon which the cover of the box is to be fitted, but
this is not to be wholly done yet, and you may proceed to hollow it out
as soon as you have turned down just so much of this flange as will show
you how much to leave in hollowing out the box. If you _fit_ the cover
before you have hollowed out the box, you will have the mortification of
finding it a great deal too loose when the box is finished, because the
latter will contract in size as soon as ever the solid core is removed
from it. _After_ you have hollowed it out, you must gauge the inside of
the cover, and the outside of the place that it is to occupy, with the
in-and-out callipers, or with a common pair, and turn the flange till
it is almost correct to this gauge, and only a very little larger than
it ought to be. When this is the case, do not trust any longer to the
callipers, but try on the cover again and again until you get a nice fit.
You must finish the flange with a chisel, held flat; and again I repeat
the caution about keeping it truly square, so that the cover will hold
equally tight in all positions. When this is the case, leave it on, and
give a last touch to both box and cover together, when you ought barely
to be able to see the joint.
You have now only to cut off the box as you did the cover, using the same
precautions. Before it is quite severed, however, you should give it a
polish. Pick up a handful of shavings, and while the work is revolving as
rapidly as possible, hold them with some pressure against it. Every fibre
will be at once laid smooth, and it will look nice and bright at once.
You can varnish it afterwards if you like, or French-polish it. Varnish
is best for boxwood, and French-polishing requires special directions,
which I shall give you separately in a future page.
To be able to make a box _well_, with its cover well fitted, is to
be able to do all kinds of similar work. Yet in these may be special
_details_ deserving notice. Probably, therefore, when speaking in a
future page of particular objects which have to be turned, such special
details will be more fitting than if given here. I shall therefore pass
on to another part of the subject, namely, screwed and twisted work.
SCREWS AND TWISTS.
Neither of these can be very accurately made without special and somewhat
expensive apparatus; but both can with practice be done tolerably well
by the young mechanic with ordinary simple means. I need not describe
a screw, for all boys know what it is; and sporting boys, of which
in these days there are many, know what sort of _animal_ a screw is.
Well, never mind. I am always riding a screw, I believe, for it is my
hobby, and there is a great deal of science in a screw; and as for the
_variety_ of the manufactured article, there is plenty of it. There is
the corkscrew, which is, after all, not a screw, but a twist,—and this is
often the means of making men screwed; and the miserly screw, who skins
fleas for the sake of their fat; and there is the mythical, invisible,
moral (and im-moral) screw, which hard-fisted men inflict upon their
weaker brethren; and there is the gigantic screw of the _Great Eastern_
steamship; and the minute, microscopic screw of the lady’s tiny jewelled
watch.
There are several modes of cutting screws, in the lathe and out of
it. The small ones required for holding together the different parts
of machinery, as well as larger ones for the same purpose, are always
cut with stock and dies. The very small ones used by watchmakers, and
all below one-eighth of an inch diameter, are made by the screw-plate.
But when either large or small screws are required of great accuracy,
they are invariably cut in the lathe, and with the aid of mechanical
appliances of the most delicately accurate description. These are all
metal screws. But the young mechanic will often wish to put screwed
covers to his boxes, and to join various parts of his work by screwed
connections instead of glue; and all these may be cut in the lathe
by simple hand-tools skilfully applied, although the operation is
sufficiently fraught with difficulty to require a great deal of practice
before it can be done with certainty of success. At the same time, my
young friends cannot possibly do better than practise this operation, for
there are numberless cases in which screws cannot be conveniently cut in
any other way, and it is, further, an accomplishment that will at once
stamp them as skilful workmen.
[Illustration: Fig. 51.]
The tools required are represented at A, B, Fig. 51. A is an outside,
and B an inside screw chasing-tool. These are always made in pairs, of
exactly the same pitch, _i.e._, the outside tool being applied to the
inside, the respective notches and points will exactly fit into each
other. If you were to examine the under side of these tools, shown at C,
you would notice that the notches do not run straight, but slanting. They
are in fact parts of screw threads; and you could make a tool of this
kind out of a common screw nut, as I have shown you at D, only it would
be too much hollowed out to make a good tool.
Now, supposing you were to hold the tool A flat on the rest, while a
cylindrical piece of wood revolved in contact with it, you would cut
a series of rings only; but if you were at the same time to slide the
tool sideways upon the rest, so that by the time the wood had revolved
once, the first point of the tool would have just reached the spot which
was occupied by the second when you started, you would have traced a
screw thread of that particular pitch. This is what you have to learn
to do always, and with certainty, no matter what pitch of tool you may
be using, and it is easy to understand how difficult the operation must
be to a beginner. Indeed, there are numbers of otherwise good turners
who have never succeeded in mastering this work. Nevertheless it can
be done, and, although difficult, it is not so much so as might be
supposed. Indeed, at first sight it would hardly be believed _possible_,
because each different pitch of tool, and each different-sized piece of
work, requires a different speed of traverse to be given to the tool.
But a practised hand will strike thread after thread without failure,
and those whose trade is to make all sorts of screw-covered boxes and
similar articles, will execute the work with as much speed and apparent
ease, as they would any ordinary operation of turning. I shall tell
you by and by, however, of several ways to escape this difficulty
of screw-cutting,—lathes being fitted in various ways to insure good
work, in some cases by carrying forward the tool at exactly the right
rate of traverse, and at others by moving along the work itself at the
proper speed, while the cutting tool is held immovably fixed in one
position,—and I will give one tool of great service which will guide you
in starting the ordinary chasing-tool; and a good start is here truly
“half the battle.”
The chasing-tool must run from right to left for an ordinary right-handed
screw (and a left-handed one is very seldom required), so that the young
mechanic need not trouble himself about it. Precise directions cannot be
given further than to have a rest with a very smooth and even edge, which
will not in the least hinder the traverse of the chasing-tool, and to
get the lathe into steady, equable motion. Then hold the tool lightly,
but firmly, keeping it at right angles with the work. Allow it only
just to touch until you find you have got into the right _swing_. It is
all a matter of knack and practice; and if you succeed quickly, you may
congratulate yourself.
The inside chasing-tool is used in precisely the same way, running it
from the outer edge of the hole inwards. To some this is an easier
tool to use than the outside chaser. I cannot say that I find it so;
especially as one has to work more in the dark; unless the work is
of large diameter like the cover of a box, and even then the work
is sufficiently difficult owing to the shallowness of the lid, which
necessitates the instant stopping of the tool for a fresh cut. For
you must understand that you have to deepen the screw-threads very
gradually, and it will take several traverses of the tool to cut them to
a sufficient depth.
The chasers require to be very sharp to cut wooden screws neatly, but
observe you must only rub the upper flat face upon the oilstone, or, if
a notch has been made by using the tools upon metal (they will cut brass
well with care), grind them in the same way; the great secret being to
hold the tool quite flat on the stone. You will thus, even by continual
grinding, only thin the blade of the chaser, which will thus last for a
long time. A practised hand will even cut a good thread with any flat
piece of steel filed into equal notches, but a screw-chaser is the only
tool really fit for the purpose.
[Illustration: Fig. 52.]
The most effectual remedy for the screw-cutting difficulty, is
unfortunately rather expensive in its best form. But in another, it is by
no means costly; and although it may not look so well as the first, it
is equally effective, and extensively used by the turners at Tunbridge
Wells, who make those beautiful little inlaid boxes and other articles. I
shall explain this to you, therefore, first:—
A, is a lathe-head, something like the one I have already described,
but you will notice that the mandrel is a much longer one, and has
several short screws cut upon it, each one being of a different “thread”
or “pitch.”[1] This mandrel runs through two collars, so that, besides
turning round, it can be pushed endwise. Now, supposing I was to hold
the point of a tool firmly against either of the screws, and at the same
time was to turn the pulley and mandrel, you will understand that it
would run backwards or forwards in its collars, at such a rate as the
screw-thread compelled it to move. This is the plan of the traversing
mandrel; and now supposing that you had a box held as usual in a chuck,
and while the mandrel was compelled to move endwise as described, you
were to hold a pointed tool against it, the tool would evidently cut a
screw-thread of exactly the same pitch as that upon the mandrel against
which the pointed tool first spoken of was applied. But in practice, a
single-pointed tool held against the mandrel would not answer very well,
and so the following plan is adopted instead, which answers perfectly.
Fig. 52, C, is called a half-nut. It has a set of screw-threads, cut
where the semicircular hollow is, which threads fit one of the screws on
the mandrel. A whole row of these half-nuts are fitted to turn at one
end upon a long bar, so that either one can be raised up at pleasure to
touch the screw upon the mandrel, which has threads of the same pitch
as itself, B. These, then, are ranged under the mandrel, and when it
is desired to make it traverse in its collars, one of these half-nuts
is raised and kept up by a wedge placed underneath it. When no screw
is required, a somewhat similar half-nut, but with merely a sharp edge
instead of a thread, is raised, and this edge falls into a notch or
groove turned upon the mandrel, or sometimes a back centre-screw is added
like D, and when no screw has to be cut, this is run up against the
mandrel like an ordinary lathe.
In the more expensive traversing mandrels, although the principle is the
same, there is a little difference in the arrangement of the different
parts. The mandrel is not very much longer than usual; and it has no
screw-threads cut upon it. But a number of ferules like K, are made each
with a screw upon its edge, and one of these of the desired pitch is slid
upon the end of the mandrel at _b_, fig. P, and is there held by a nut or
otherwise, so that it cannot move out of its place. The half-nut is seen
at _a_. It consists of a piece of brass or steel of the form shown with a
hole in the middle, and a screw cut upon _each hollow_, so that it is a
circle or set of half-nuts of different pitches. This slips over a pin at
_a_, and when the screw _b_ is turned, it draws up this pin and the nut
attached, until the latter comes in contact with the ferule upon the end
of the mandrel. This is very neat but expensive. Now, by far the cheapest
and best way for the young mechanic, is to set boldly to work to conquer
the difficulty of chasing screws by hand. There are even disadvantages
in the expensive form of a traversing mandrel, which render it by no
means a desirable mode of fitting up a lathe, and after all, the length
of screw which it enables one to cut is very limited, and in addition,
it is not every day, nor probably once a month, that screw-cutting will
be necessary at all. My advice, therefore, is, do not get a traversing
mandrel until you can cut screws well with the chaser. When you can do
this, you will be able to judge of the advantage or disadvantage of one.
By far the greater number of common screws are cut without the lathe,
by screw-plates, or stocks and dies, and the nut, or hole into which
such screws are to fit, is cut with a tap. A screw-plate is a simple
affair,—a mere flat plate of steel, in which several holes are drilled,
which are afterwards threaded by screwing into them taps, or hard cutting
steel screws of the size required; the plate is then hardened by being
heated red-hot and suddenly cooled, after which being much harder than
brass, iron, or steel which has not gone through such process, it will
in turn cut a thread upon any of these by simply screwing them into it.
But although this will answer for small and common screws, it is not at
all suitable for better ones, because the thread is _burred_ up, not
_cut_ cleanly as it would be with a proper tool. A far better plan is a
stock and dies; the latter being practically a hardened steel nut sawn in
half, and fitted so that the two halves can be pressed nearer and nearer
together as the screw thread becomes deeper. The dies are screwed up by
means of a thumbscrew opposite to the handle.
To use it, a piece of iron is filed up or turned to the required size,
which must be exactly that of the finished screw. The dies are then
loosened and slipped on to the end of this screw-blank as it is called,
and are then slightly tightened upon it. All that is now required is to
keep turning the tool round and round upon the pin, which it will soon
cut into a screw thread. When the stock is at the bottom or top, you may
tighten the dies, and so work up or down; but never tighten them in any
other part. If iron or steel is to be cut, use oil with the tool, but
brass may be dry. If the screw is of steel, heat it red-hot and let it
cool very gradually, to make it as soft as possible.
The hole or nut, into which the screw is to fit, is to be drilled so as
just to allow the taper tap to enter about a couple of threads; a wrench,
or, if small, a hand-vice is then applied to twist it forcibly into the
hole, when the thread will be completed. Take great care to hold the tap
upright, or else, if it is a screw with a flat head which has to fit into
it, it will not lie correctly, but one side of the head will touch while
the other is more or less raised.
There are other modes of screw cutting, but at present I need only
mention one, which is used for wooden screws alone. It is called a
screw-box, and is only made to cut one size, a tap being always sold to
match. You can, however, purchase any size you like, from a quarter of an
inch to 2 or 3 inches; but the latter are only intended for very large
screws, such as are used for carpenters’ benches and various kinds of
presses. A screw-box looks like a small block of wood with a hole in it,
but if you take out two screws you will find a blade of a peculiar shape,
which forms the thread by cutting the wood as it is screwed into the hole
in the box.