Among the valuable lessons on offer in “Mechanic’s Companion” are the “Explanation of Terms used in…” at the end of every section – quick definitions of the jargon, with reference to where they’re covered in the text for further reading and elucidation.

Below is the “Index and Explanation of Terms used in Turning:”

N. B. This Mark § refers to the preceding Sections, according to
the Number.

A.
Axis, an imaginary line passing longitudinally through the middle of the body to be turned, from one point to the other of the two cones, by which the work is suspended, or between the back centre and the centre of the collar of the puppet, which sup­ports the end of the mandrel at the chuck.

B.
Back Board, that part of the lathe which is sustained by the four legs, and which sustains the pillars that support the puppet bar. The back board is only used in the best constructed lathes. In the common lathes, the shears or bed are in place of the back board, § 5.
Back Centre, See Centres, and § 5
Band, § 5. See also Cat-gut.
Bearer, that part of the lathe which supports the puppets. § 5
Bed of the Lathe, the same as bearer, which see 3.2.
Boring Collar is the machine having a plate with conical holes of different diameters ; the plate is moveable upon a centre , which is equidistant from the centres or axes of the conic holes; the axes are places in the circumference of a circle. The use  of the boring collar is to support the end of a long body that is to be turned hollow, and, which would otherwise be too long to be supported by a chuck. See Plate XXXV. Fig. 2.

C.
Callipers, compasses with each of the legs bent into the form of a curve, so that when shut, the points are united, and the curves being equal and opposite, enclose a space. The use of the callipers is to try the work in the act of turning, in order to ascertain the diameter or diameters of the various parts. As the points stand nearer together at the greatest required diameter than the parts of the legs above, the callipers are well-adapted to the use intended.
Cat-gut, the string which connects the fly and the mandrel, § 5.
Centres, are the two cones with their axis horizontally posited for sustaining the body while it is turned, § 5.
Cheeks, the shears or bed of the lathe as made with two pieces for conducting the puppets.
Chisel, a flat tool, skewed in a small degree at the end, and bevelled from each side, so as to make the cutting edge in the middle of its thickness, § 9.
Chuck, a piece of wood or metal fixed on the end of the mandrel for keeping fast the body to be turned, § 6.
Circular Turning, § 2.
Collar, a ring inserted in the puppet for holding the end of the mandrel next the chuck, in order to make the spindle run freely and exactly, § 5.
Collar Plate. See Boring Collar.
Connecting Rod. See Crank Hook.
Conical Points, the cones fixed in the pillars for supporting the body to be turned; that on the right hand is called the fore cen­tre, and that on the left hand, the back centre, § 5.
Crank Hook, sometimes called also the connecting rod, as it con nects the treadle and the fly, § 5.
Crank, the part of the axle of the fly, which is bent into three knees or right angles, and three projecting parts; one of the parts is parallel to the axis, and has the upper part of the crank hook collared round it, § 5.

D.
Drill, § 14.

E.
Elliptical Turning, § 25.

F.
Feet, the horizontal pieces on the floor which support the legs of the lathe, § 5.
Flat Tools, § 17.
Fly Wheel, § 5.
Foot Lathe, § 5.
Foot Wheel, or Fly, the wheel or reservoir for preserving and continuing the motion when the force applied by the foot is not acting, § 5.
Fore Center, that on the right hand. See Centres, § 5.

G.
Gouge, the tool for roughing out the work, § 8.

I.
Inside Tools, § 15.

L.
Lathe the machine for holding and giving motion to the body to be turned, when the requisite force is applied.
Lathes, in general use, § 3.
Left-side Tools, § 11.
Legs, the uprights mortised into the feet for sustaining the upper part of the lathe, § 4, 5.

M.
Mandrel, that part of the lathe which revolves the body when turned in a chuck: the pole lathe has no mandrel, § 5.
Mandrel Frame, the two puppets which hold the mandrel; a hardened steel collar being fastened in the fore puppet, and a screw with a conical point in the back puppet.

N.
Nose, that part of the spindle of the mandrel which projects over the puppet to receive the chuck, § 5.

O.
Oval Chuck, § 25.

P.
Parting Tools, § 21.
Pikes, now called conical points, which see.
Pillars, the uprights fixed at the ends of the back board, for supporting the bed of the lathe or puppet bar, § 5.
Pitched, is the placing of the work truly upon the centres.
Point Tool, § 13.
Pole, an elastic rod fixed to the ceiling of the turner’s shop for re-acting by means of the string upon the treadle against the pressure of the foot; the foot draws the string downwards, and the pole exerts its force in drawing it upwards, and consequently should have no more elasticity than what is sufficient for this purpose, as the overplus would only tire the workman, § 4.
Pole Lathe, § 4.
Pulley, § 5.
Puppet Bar. See Bearer.
Puppets, the upright parts for supporting the mandrel, the one on the right being called the fore puppet, and that on the left the back puppet; the screw is fixed on the one, and the mandrel collar on the other puppet, § 5.

R.
Rest, the part of the lathe which sustains the tool while turning, § 4, 5.
Right-side Tools, § 10.
Roughing Out, is the reducing of the substance by means of the gouge, to prepare the surface of the body for smoothing.
Round Tools, § 12.

S.
Screw, the conical points or centres as made with a screw, in order to tighten the work; the screw or screws ought to be kept so tight, that there should be no play, otherwise the work may be in danger of flying out, § 5.
Screw Tools, § 16.
Sheers. See Cheeks or Bed of the Lathe.
Slider, § 25.
Square Tools, § 18.
String, that which connects the treadle and the pole in the pole lathe, and in the foot lathe it passes round the fly-wheel and the pulley of the mandrel in order to turn the latter.
Swash Work, § 29.

T.
Tools, § 7.
Traversing, is moving the gouge to and fro in roughing out the work.
Treadle, the part of the lathe by which the foot communicates its force, and gives motion to all the other moveable parts, § 5.
Triangular Tools, § 19.
Turning in General, § 1.
Turning Gravers, § 20.

W.
Wabble is the shaking of the work in the act of turning, because it is not fixed truly upon the centres.

There are several other terms which are common to smithing and turning. See the Index and Explanation of the Terms to those articles.

Excerpted from Peter Nicholson’s “Mechanic’s Companion.”

Editor’s note: “Wabble” is charming.