1. Turning is a very useful art, by which a great variety of articles
are almost exclusively manufactured. Besides this, it constitutes a
considerable part of the operations of several trades and occupations,
such as the chairmaker, machinist, cabinet-maker, brass-founder, &c.,
since every substance of a solid nature can be submitted to the
process.
2. Turning is performed in a _lathe_, an apparatus constructed in
various ways, according to the particular purposes to which it is to
be applied, although, in all cases, the general principle of its
operation is the same. The kind represented in the above picture, is
used for plain or circular turning in wood. On examination, it will be
perceived, that two wheels of different sizes make essential parts of
it. On the extended axle of the smaller one, is fastened the piece to
be turned; and immediately in front of this is the _rest_, on which
the cutting instrument is supported during the performance of the
operation.
3. When the material to be turned is wood, it is commonly cut to the
proper length with a saw, and brought to a form approaching to the
cylindrical by means of an axe or drawing-knife. It is next fastened
in the lathe. This is done by different means, varying according to
the particular form of the thing to be turned. In plain circular
turning, as applied to bed-posts, legs of tables, and rounds for
chairs, the piece is supported at each end. That at the left hand is
driven upon a piece of steel, which has been screwed upon the extended
axle of the small wheel; and the other end is fixed upon a steel
point, placed in an upright moveable piece called a _puppet-head_.
4. In case the wood is to be turned on the inside, as in making a
bowl, cup, or mortar, the piece is supported altogether at one end, by
means of a hollow cylinder of wood, brass, or iron, called a _chuck_,
which receives it on one side, and on the other is screwed upon the
end of the axle. The axle is sometimes called the _mandril_, and any
extension of it, by means of a piece added to it for a centre, on
which anything may be turned which will admit of a hole through it, is
denominated an _arbor_.
5. The tools used in turning wood and ivory, are _gouges_ and
_chisels_ of different sizes and shapes. In using these, they are
placed upon the _rest_, and brought in contact with the revolving
material of the proposed figure. The gouge is employed in cutting away
the rough exterior, and the chisel, in producing a still further
reduction, and a greater smoothness of surface.
6. In working in very hard wood and in ivory, the _grooving tool_, a
sharp pointed instrument somewhat similar to the graver, is used in
the first part of the operation; and by this the grain of the
substance is cut into contiguous grooves, and prepared for an easy
reduction by the chisel. The instruments for turning metals are
numerous, but they differ in some respects from those for cutting
wood.
7. In almost every kind of turning, a tool called the _calipers_ is
necessary for measuring the diameters of the work. In its form, it
bears some resemblance to the compasses or dividers. One or both of
the legs, however, are curved; and one kind of this instrument has
four legs, two curved, or two straight, at each end, with a pivot in
the centre, on which it is opened and shut. The former of these is
employed in measuring the dimensions of outside work, and the latter,
for that on the inside. This kind is called the _in-and-out_ calipers;
and it is especially useful in turning a cylinder, or pin, which shall
exactly fit an internal cylinder already made, and _vice versâ_.
8. There is but little difference in the management of turning
different substances. The principal thing to be attended to is to
adapt the velocity of the motion to the nature of the material; thus
wood will work best with the greatest velocity that can be given to
it. Brass should have a motion about half as quick as wood, and iron
and steel still less; for, in operating on metallic substances, the
tool is liable to become hot, and lose its temper; besides which, a
certain time is requisite for the act of cutting to take place.
9. When compared with many other mechanical operations, the art of
turning may be considered as perfect in its accuracy and expedition.
The lathe is, therefore, resorted to for the performance of every work
of which it is capable; nor is its use confined to the production of
forms perfectly cylindrical, for it can be easily made to produce
figures of irregular shape, such as lasts, gunstocks, &c.
10. The lathe was well known to the Greeks and Romans, as well as to
many other nations of antiquity. Diodorus Siculus, who wrote in the
time of Julius Cæsar and Augustus, says that it was invented by one
Talus, a nephew of Dædalus. Pliny ascribes it to Theodore, of Samos,
and mentions one Thericles, who had rendered himself very famous by
his dexterity in managing the lathe. The Greek and Latin authors
frequently mention this instrument; and, among the ancients, it was
customary to express the accuracy and nicety of a thing by saying, it
was formed in a lathe.
[Illustration: CABINET MAKER.]