An Axis Of Rotation

That line which remains at rest in an axle while the axle rotates; whether the axle rotates around one of its longitudinal axes or around one of its minor axes. An excentric cam on a shaft rotates around one of the cam's minor axes, and this axis is the straight line through the hole in the cam. A crank-lever on a shaft rotates around that minor axis of the lever which is a line through the centre of the hole in the boss.

An Axle

A piece of machinery which is intended to be itself rotated, or intended for something to be revolved on the axle.

Back-Lash

In machinery, back-lash is an amount of space which allows one piece of a machine to be moved forward and backwards a short distance, without moving the piece with which it works. In two cog-wheels in gear with each other, the back-space is the distance that one wheel may be rotated without moving the other. The back-space or back-lash of a screw and its nut is the distance which the nut may be moved forwards or backwards without rotating either the screw or the nut.

A Bearing

The bearing of an axle or joint-pin is that portion which is in immediate or direct contact with the bearing-brass or other bearer. The principal bearing of a piston-rod is the portion that is in contact with the packing in the packing-box; and a thrust bearing includes all its ridges and all the necks between.

A Bearer

Bearers in machinery include brasses for axle-bearings, bushes, blocks, slides, guides, and many others ; and are used in a variety of positions.

A Bed

The bed of a lathe is part of it, being that which sustains the entire movable portion of the apparatus, including the mandril-frame, wheels, poppet-head, carriage, slide-rest, screwing gear, and traverse gear; but the foundation on which the lathe rests is a bed of timber, stone, or some other material distinct from the lathe. The bed of a steam-hammer's framing is its foundation.

A Belt

In machinery, a belt is an endless band of leather or other material in contact with the rims of two wheels for the purpose of communicating motion from one wheel to the other.

A Bevel

The bevel of a chisel is its cutting part. The bevel of a valve is the part which bears on the valve-seat. To bevel is to make a bevel on a piece of machinery by means of filing, forging, or some other method.

A Blow

A knock. An amount of knocking or percussive force imparted from one body to another.

A Bolt

A stick, rod, or bar, intended to move in the direction of its length. In machinery bolts are used for fixing pieces of work to each other ; and may be either key-bolts or screw-bolts. To bolt is to fasten by means of a bolt, whether it has a screw or not.

To Bore

To make a hole by means of a rotatory motion, which is applied either to the object to be bored or to the boring tool. A bore, is a general term applied to any tubular opening. To bore a wheel is to make a hole, or enlarge a hole, into the wheel by means of boring; and while the hole is being made, the wheel is bored, but not the hole.

A Boss

A boss of a rod, lever, or shaft, is a thick portion adjoining a thinner, or between two thinner portions. The fulcrum boss of a lever is always the strongest when compared with any other bosses of the lever. A boss may be globular, cylindrical, hexagonal, and of many other shapes, and may be with or without a hole.

A Brass

A bearer or covering made of brass or gun-metal, placed to some part of an axle or rod to sustain its friction. A couple of brasses are named a pair, when the two brasses are so shaped that both are required for one axle-bearing; consequently, each of the two brasses possesses a semi-cylindrical gap, if intended for a cylindrical bearing; and if for a bearing of any other form, the gaps are shaped to correspond.

Brittleness

A hardness belonging to a metal or other material, which allows or admits of its being easily broken by strains of percussion or vibration.

A Bur

The bur of a piece of work is a jagged projection or number of projections; these are formed along the edges and sides of the work while being turned, planed, or otherwise cut. Burs are produced also by hammering a piece of work; and by two pieces knocking together during use.

A Bush

A bush is a piece of furniture made to fit a hole, whether the hole is cylindrical or of any other form. When bushes are required for sustaining friction, they are of gun-metal, steel, or wood. These furnishers or garnishers are used also for levers of various sorts, when it is necessary to make one lever fit spindles of different sizes; in such cases, the garnishers may be square or hexagonal. To bush a joint-hole is to adapt a bush to the hole; and to bush a joint-pin or bolt is to adapt a bush to the bolt instead of the hole.

A Cam

A class of bosses that extend from one side of levers and axles, instead of both sides. An excentric cam is a wheel having a hole which is not in the middle. A lever-cam is a projection on one side of a lever-boss. A solid cam is one which is solid with the axle or lever, instead of being keyed or bolted to it.

A Calliper

An instrument for measuring the bore of a gun. Callipers are used to measure lengths, widths, and thicknesses, and each calliper consists of two legs jointed together by means of a pin, which is fixed in the thick ends of both legs. Legs of callipers are both straight and arched. To calliper is a useful verb, signifying, to measure with a calliper. One calliper is often named a pair, because its two legs are of the same shape.

To Cast

To pour melted metal or other material into sand moulds or other moulds. Cast steel is that which is poured after being made into steel.

To Calk

To calk a boiler consists in thickening the overlying portions of the plates, after they are riveted together; this calking is performed with hammers and punches. The calking of joints in engine-work is effected by driving cements of various sorts into narrow openings provided for the purpose.