ASSEMBLE, a term of great significance in modern produc tive methods. It explains the difference between the older practice of fitting parts to one another, and the modern way of finishing components so that they can be brought together or "assembled" without the need for any cutting or alteration; if spares and re placements are needed, they may then be supplied in tens of thou sands, all certain to fit without alteration.
There is of ten a modified procedure in manufacturing parts of large and elaborate structures, the primary assembling being done at the works, with a moderate amount of hand fitting, and then all the joints are marked with paint or stencilling for the final assembly in situ. Perfection of assembling occurs in the smaller all-metal products and parts such as screws and bolts, brass fit tings, steam and water valves, ball bearings, clocks, typewriters, sewing-machines, magnetos, small arms, machine-guns, cartridges, shells, small engines, pumps and motor cars. The practice origi nated in the United States because of the great demand for sewing machines and small arms, and later for typewriters.
An elaborate equipment and routine system becomes necessary to make parts ready to assemble. All the cutting tools on the machine-tools must keep their size for a certain period without wear, and to test the results therefrom numerous gauges have to be employed, the germ of the system being the "limit-gauge." This has two measuring portions, called and marked the "go" and "not go." No machine tool can cut or grind a piece of metal to exact size (commercially), but if a definite limitation of error each way is ensured, then the piece will assemble with its other compo nent. Hence the limit-gauge is made oversize one end, say 4 in. plus one 2,000th of an inch, and undersize at the other, one 2,000th of an inch less than 4 inches. A shaft must, therefore, be made of such diameter that it will neither be too large to pass into the -}- opening of the gauge, nor so small that it will pass into the — opening. Thus the limits of size are guaranteed.
The assembling department of a factory may contain merely benches, with bins full of the parts within reach, the assemblers putting the details together without any special holding arrange ments, the product being taken away by hand or trucks. This is not a suitable system for the larger articles, and conveyor outfits have to be installed, such as plain rails on which the objects are moved away, travelling chains or plates, turntables, etc. Motor cars are assembled while running on dummy flanged wheels rolling on rail tracks, each assembler adding some portion as the chassis reaches his standpoint. Motion-study becomes essential in these highly organized systems, and special tools greatly assist, such as ratchet screwdrivers and spanners, screwdriver braces, and pneu matic and electric wrenches for rapid rotation without labour. (See