TOOLS.
Any one who has watched a novice at work on a lathe, must have remarked
the difficulty he has in controlling the tool and keeping up the motion
of the treadle at the same time. The two operations are difficult to
“get the hang of,” to use a homely phrase; but once conquered, the work
can proceed. The natural tendency is to slack up or stop the motion of
the treadle while the tool is engaged, and the tool is, therefore, at
one time under the work, at another time above it, at another jumping
rankly in, until, finally, the piece goes whirling out of the center or
the chuck, and the operator flushes all over at his awkwardness.
This, of course, is remedied by practice; and as this work is written
mainly for the information of beginners and amateurs, we hope that
experts and those who know all about hand lathes, will excuse allusion
to such simple things as holding the tool properly, and kindred matters.
The lathe must be of such a height as the workman finds convenient, so
that he is not obliged to stoop much, and, at the same time, low enough
to allow the weight of the body to be thrown on the tool when hard work
is to be done. The speed of the lathe ought to be very high on the
smallest cone, and there should be three speeds, at least, for
different work. The object is to regulate the velocity of the work in
the lathe, and keep the motion of the treadle uniform, as near as may
be, at all times. It distresses a workman greatly, when chasing a fine
thread on a small diameter, if he has to tread fast to get up the
proper speed, as he does when there are only two speeds. On the
contrary, for larger jobs, it is difficult to keep up a rotary motion
if the foot moves slowly, as it must in order not to burn the tool by a
high velocity on some kinds of work. Foot lathes, in general, are not
geared, although some are, and ought to have wider ranges of speed than
they do. Where one class of work is done, however, it makes little
difference, but for general turning, the speeds should vary.
Another difficulty experienced by beginners is in holding the tool
still—_rigidly so_. They allow it to “bob” back and forth against the
work, if it runs untrue, so that it is impossible to make a job. The
tool must be held hard down, as if it grew to the rest, and never
moved, nor receded, until the cut begun is finished.
The “rest” should be of soft, wrought iron, since that material holds a
tool with more tenacity; imposing less strain on the arms of the
operator. It should be dressed off smooth as often as it gets badly
worn, or cut by indentations. Cast iron is not good, and steel is not
so good as wrought iron. A special rest should be kept for chasing
threads with, since the least obstacle is enough, when running up a
fine thread, to divert the chaser and spoil the job, by making a
drunken thread. If we now suppose the lathe to be in good order, the
centers true and well-turned to a gauge, the rod (if that is the job)
between them and properly “dogged,” the centers oiled, and the rest at
the right height, we shall be all ready to start. The rest should be
high enough to bring the point of the tool a little above the center.
[Illustration: Fig. 3.]
To rough off the outside, and make it run true, is the first step, and
the tool must, therefore, be held as in Fig. 3, or so that the point
and part of the edge alone engage with the work. This will take off a
thin, spiral cut, without springing the shaft or making it untrue. The
whole surface of the shaft must be thus run over, beginning at the
right hand and shifting the tool as fast as one part is turned. The
tool should not be moved rigidly in a straight line toward the belt,
but by holding it hard down on the rest, so that the bottom edge bears
as in Fig. 2, and rocking the tool on that angle, so that the point
describes a curve, as in Fig. 4, the work will be turned evenly and
true.
[Illustration: Fig. 4.]
We must remark, in passing, that the person who reads these directions,
and then undertakes to turn by them, will find that reading how to do a
thing, and doing it, are two different matters.
It looks very nice to see a skater darting over the ice at his ease,
but try it once, and, if you never knew before, you will understand
what experience means. Trying to teach a person to be a turner, in a
book, is analogous. One can only indicate the general method, and leave
experience to do the rest.
[Illustration: Fig. 5.]
After the whole surface has been run over, the same tool may be used on
the flat side for reducing the work to one diameter throughout the
length. The reader must not assume that there is no other tool than a
diamond point; he will find many others adverted to, as we proceed.
[Illustration: Fig. 6.]
It is most important that the ends of a rod or shaft should be squared
up first, before the body is turned, for the removal of some slight
inequality subsequently may cause the whole shaft to run out of truth.
The center must be drilled with a small drill, and slightly
countersunk. When the end is squared up, the center must be run back a
little, so that the tool point may project over the drilled hole, and
thus make it all true about the center, as in Fig. 5. This will make
the work push over to one side of the center, but that is of no
consequence. Let it run as it will; so long as it does not come out of
the centers there need be no apprehension.
Fig. 6, is another kind of roughing tool, to do heavier work with.
[Illustration: Fig. 7.]
There are two kinds of tools used in foot lathes, called straight and
heel tools. Fig. 7 is a heel tool. It is so called from the heel which
is forged on the lower end. One form of the straight tool has already
been shown. The heel tool is used on heavy work, and the object of it
is apparent, namely, to hold on the rest, and so impose but little
labor on the workman to retain it in place, or prevent it from
receding. It is generally forged from half inch or five eighth steel.
The steel is held in a handle twenty inches long, grooved on top to fit
the steel, and furnished with a handle at right angles. This handle has
a square eye in the top that the tool passes through. A nut at the end
of it screws up the eye and binds the tool fast in the groove, so that
it cannot slip.
It is given complete in Fig. 7. The lower handle enables the workman to
have great power over the edge, and to direct it from or to the work
without danger of catching. The tool is used by resting the end on the
shoulder, as in Fig. 8, and turning the lowest handle. Since the heel
holds the tool from slipping, there is no occasion to bear against it.
In fact, there is no occasion, at any time, to force the tool from the
workman, but it must be turned sideways, back and forth. A piece,
properly centered, may be cut in any way without destroying its truth.
[Illustration: Fig. 8.]