MACHINERY em braces the various machines employed to re duce the timber as cut in the forests into lum ber, shingles, doors, sashes, moldings, veneers, barrels, buckets and the endless variety of wooden objects and contrivances used for in dustrial purposes. As the woods upon which they arc used vary in many qualities from the docile white pine to the difficult elm and the almost metallic hardness of the ebony and toughness of the lignum vita, their variety and adjustments must be almost numberless. They may be conveniently divided into four general classes—saws, which operate by rending or scission; planers, by which the work is accom plished by a paring action; lathes, in which the wood is turned or pared while being revolved; and grinders or abrading machines, which are generally employed as finishers and accom plish the work through the medium of sand or emery. Saws are blades of steel with toothed edges and though also used to divide metal and stone, they are employed principally to divided wood. (See SAws AND SAWING; SAW-sena.). For saws used in metal-working see Mum. WORKING MACH I N ER It. The use of saws is of very ancient origin, and it is prac tically Impossible to enumerate in detail their adaptations to various mechanical processes. Among uncivilized peoples, saws were made of flakes of flint imbedded in wooden blades and held in place by means of bitumen. Later, among the ancients. bronze saws were used, but all modern taws are made of steel of the finest quality. Band saws were invented about the beginning of the 19th century. and although their particular merits were known long before the circular saws came into general use, they were not adopted until the latter part of the century, owing to the difficulty of making blades capable of withstanding the severe serv ice. But, with the manufacture of the finer grades of steel of greater tensile strength and elasticity, since 1865, they have been adopted in addition to the circular saws in many of the larger mills. They are made in sizes ranging (tom one-half inch in width, used for ordinary shop-work, to from six to eight inches in width, tor the use of the larger lumber mills. In mode of operation, which is as that of a belt over two pullers, they cut with a continuous down and motion, with the toothed edge always in the kerf. The pulle?; or guide-wheels, one of
which is the driver, range from 54 to 72 inches in diameter. The saw blades are in a continu ous band, from 45 to t) feet in length, and the saw is run at a spec (I of 4,000 feet per minute. Being made extremely thin, they are used for contintions and rapid cutting in planing mills :old other wood-working plants, where some Cuts have to he Mae in scrolls and curves, and require a %rr• flexible blade. The thinness of the bl.ole insures a much smaller kerf-waste than that resulting the circular saw, and as installed in their larger forms in the lumber mills are capable of sawing an average of 40,000 feet of lumber per day. The table of band saws used in shop-work is often made to tilt, for beveled work; or the saw blade and its pulleys may be tipped backward, for the edge of a strong cast-iron centre, which gives the required rigidity. The larger sizes range up to six feet in diameter and possess cutting edges so light that they are capable of cutting veneers almost as thin as a sheet of paper same purpose. The saws commonly known as scroll saws and jig saws are very narrow straight blades of steel, often as fine as 1/32 of an inch in width, which are operated with a reciprocating movement, and are employed to cut various ornamental designs as for brackets, corner-pieces, clock-cases, etc., and in making furniture.
Another form of veneer-cutting saw is a sin gle-bladed reciprocating saw doing its work in a horizontal position in a carriage which rises and falls in vertical guides. Another form of veneer cutter is a vertical knife against which the log of wood is revolved so as to take off a continuous shaving. Planers are used to smooth lumber and to reduce it to exact dimen Of saws used for special purposes, the seg ment saw used for cutting veneers should re ceive mention. The segment saw is circular in shape and is formed by bolting the blade seg ments, which are extremely thin, upon the outer sions by removing the rough surfaces of the product of the sawmills. In the surface planer this is accomplished by a rank of overlappirg revolving cutters which pare off shavings and leave the surface of the timber quite smooth.