METAL SPINNING.
Spinning sheet metal into various forms is another kind of work which
can be done in the foot lathe, and it is here that the amateur can show
his taste and dexterity.
The process consists in forming a blank, like this engraving, into an
ornamental base for a lamp, or an oil cup; in fact, any thing
whatsoever. All that is requisite is to have a fac simile, in wood, of
the shape you wish to make. This is bolted or otherwise made fast to
the face plate, and the blank is then set up against it, and held as
the cylinder head, shown in Fig. 26, is, that is, with a rod leading
from the back center of the lathe to the work.
[Illustration: Fig. 31.]
A tool like Fig. 32 is then used to press the metal into all the
recesses or curves of the pattern. The speed must be high, and the
metal quite soft and moistened with a little soap-suds or oil, so that
it will not be scratched by the tool.
To spin metal requires some dexterity, but it is easily acquired after
a little practice. The rest must be furnished with holes, like Fig. 33,
and a pin, so that the tool can be brought up against it like a lever.
[Illustration: Fig. 32.]
[Illustration: Fig. 33.]
Still-another kind of metal spinning can be done in the lathe. This
relates to making circular shapes, or cylindrical, more properly—such
as napkin rings, the tops of steam pipes, or similar things. To do
this, a mandrel is requisite. The mandrel must be of steel, and turned
to the desired pattern—like Fig. 34, for instance.
[Illustration: Fig. 34.]
A ferrule is then made and soldered together with lapped edges, so that
there will be no seam. The mandrel must be as much smaller than the
size of the finished work as will allow it to come off freely, for it
will be apparent that if the work was spun up _on_ the mandrel, it
could never be taken off. The ferrule, when put on them, will stand
eccentric to the mandrel, as in this figure—that is, when the tool
bears on it. In other respects the process is just the same as spinning
on the face plate. Tripoli, chalk, whiting, rotten-stone, and similar
substances are used to give the fine polish on such work.
[Illustration: Fig. 35.]
We know of no prettier or more expeditious process of making a small
steam boiler for a toy engine, than by spinning it upon the lathe. The
boiler will be very strong, have large fire surface, and be without
joints, having only one at the bottom, where it is easily kept tight.
Fig. 36 is the boiler.
The metal must be thin (twenty gauge), the sheet brass sold in the
shops will answer, as it is already annealed, and the corrugations must
not be too deep on the sides, or the work will not come off the mould.
The center of the fire-box, A, must be left flat, so that the flue will
have a bearing on it. For a small engine, 1-inch bore, and 2-inch
stroke, a boiler of the dimensions given here is ample. The flue must
be brazed or soldered at A, and the bottom must be riveted at B, for
every two inches; this is not necessary, however. There are only three
pieces in this boiler—the shell, the fire-box, and the flue, and the
water must not be carried more than three-fourths of an inch over the
crown of the furnace.
We shall now again revert to cutting tools.
[Illustration: Fig. 36.]
Probably many of our readers, who use hand lathes not furnished with
slide rests, have wished for that indispensable appendage where boring
is to be done. For ordinary turning, we do not appreciate a slide rest
on a hand lathe so much as many do that we know, but for boring out
valves, cocks, or, in fact, anything, a scroll chuck and a good slide
rest are invaluable.
Some persons are always “meaning” to do a thing, yet never do it.
Sometimes, for the want of facilities, at others for the lack of an
idea. If the latter be of any value, we can furnish one or two on this
subject that may be useful.
[Illustration: Fig. 37.]
One way to bore out holes parallel, without a slide rest, is to do it
with the spindle of the back head. With a tool of peculiar
construction, holes varying in size, can be bored beautifully in this
way. We present a view of such a tool in Fig. 37. It is merely a cross,
formed on the end of a center fitting the back spindle, the same as the
lathe center does. The arms of the cross are made stout and thick, so
as to admit of a square hole being cut in them. The hole is made by
drilling in and driving in a square drift afterwards to take off the
corners. The shanks of the tools are well fitted to these holes in the
arms, so that a slight pressure of the screws in the sides of the arm
will hold them steady. When used, the tool is put in the back spindle,
and the cutters set to the size required, or less, if there is much to
take out, and run through the work in an obvious manner. Any range of
size can be had up to the diameter of the cross. It is not well to run
the cutters out too far, however, as they will jump and chatter, or
spring, and make bad work. The tool is so easily made that one can
afford to have three or four, for different jobs.
[Illustration: Fig. 38.]
Another plan, but not so good, is to make a common center and disk,
like Fig. 38.
Here the cutters have a slot in them, through which a bolt passes and
screws into the disk; a small piece of wood put at the bottom of the
tool, between it and the cutter, prevents it from slacking off so as to
diminish the cut. These tools will be found useful, and will do good
work if properly handled. This latter tool is better for wood, but will
answer for any metal by varying the cutter.
To make a slide rest, in the common way, is a costly and tedious job.
For all purposes of boring, a good one may be made as shown in the
following engraving, Fig. 39.
[Illustration: Fig. 39.]
This is simply a casting fitted with a screw and spindle, as shown. The
spindle has a tool let in the front end and held there by a set screw,
and there is a wheel at the back end to run the spindle in and out. The
casting has a leg to it which enables it to fit the common post the
rest for the hand tool fits. There is also a key to prevent the spindle
from turning round. By this arrangement it is easy to bore, not only
parallel holes of any size, but tapering ones, which is often a great
convenience. By a simple change of tool, it can also face off any
casting, and can easily be made to cut a thread, of a given pitch, by
any ingenious workman. Not only this, but it can also be made without
planing; or other work most amateurs have no facilities for. It is
within the range of ordinary lathe work, and will be found
indispensable. The T-head may be of cast iron, but the spindle should
be steel, with a brass nut let in the back end for the screw to work in.