METAL-WORKING TOOLS.
All the work performed upon metals for the purpose of fashioning them into tools, implements, and appliances of various kinds is effected either by cutting, abrading (including polishing), or bending, to which processes those of stamping, flanging, and punching arc related in various degrees. All these mechanical operations, more particularly those of bending, punching, and are dependent on the property pos sessed by all solids, and especially by metals, of spreading under pres sure, and in many cases the line of demarkation between one process and another is very difficult to trace. Thus in sonic machines the process of cutting frequently shades off into that of abrasion and the process of stamp ing into that of bending.
The term "machine-tools" has by common consent been adopted to designate those machines which are employed in working iron by purely mechanical operations. They supplant metal-working hand-tools, just as wood-working machinery supplants wood-working hand-tools; but, while wood-working machines are to be considered as machine-tools no less than those for working metal, the usage of the trade has made and maintained the distinction between machine-tools and wood-working machinery.
Class cation.—The principal varieties of metal-working machine tools built in the United States to October, 1889, are: (r) Lathes: axle, bolt, car-wheel, driving-wheel, die-grinding, engine, forming, gunstock, gun-hoop, hand, pattern-makers', pulley, rod, spinning, shafting, screw cutting, turret; (2) Planers: connecting-rod, crank, friction, frog and switch, open-side, pit, plate, regular, rotary, valve-seat (rotary), valve seat (reciprocating); (3) Shapers: crank, cylinder, double, geared, pillar, single, traversing; (4) Slotters: regular, screw, under stroke; (5) box (horizontal), box (vertical), chord, car-box, car-wheel, crank-pin, cylinder, hand-wheel, horizontal, link, pulley, tire, vertical; (6) arch-bar, automatic, cotter, horizontal, key-seat, multiple, portable, radial, rail, .sensitive, turnbuckle, universal, vertical; (7) Shears: angle, bar, circular, plate; (8) bolt-head, column, double, horizontal, key-seat, regular, steam-chest seat, universal, vertical; (9) cutter, lathe-centre, plain, reamer, surface, twist-drill, tool, universal; (To) cutting, heading, head-milling, threading, turning; (I r) Nui-machines: chamfer ing, facing, milling, punching, tapping; (12) Presses: crank-pin, cutting, drop, drawing, geared, hydraulic, stamping, wheel; (13) Alrseehancors iliac/lines: belt-polishing, centring, crank-pin turning, entting-off, cross head-pin turning, chucking, die-sinking, facing, forging and upsetting, gear-cutting, grooving, heading, marking, measuring, punching, plate bending, profiling, rack-cutting, rail-bending, shaft-straightening, screw making, quartering, rail-cutting, riveting (steam), riveting (hydraulic), riveting (pneumatic), tool-grinding, wheel-turning, wheel-quartering; and steam-hammers. It will be noted that there is a marked tendency toward
specialization. Under each head there are built for particular classes of work other forms than those above mentioned, but, not being in general use, they are not specified. Some of those named under " Miscellaneous " might, indeed, be classed under " Lathes," " Milling-machines," etc. The pres ent section will include a review of typical machines in each of the more important classes.
Sharpening, Grinding, and Abrading reduce the size, vary the shape, or improve the surface of metals there may be employed abrading devices, such as the file and rasp, the hone, whetstone and grind stone, the emery-wheel, and the corundum-wheel. The character of work done by these in removing material by a gnawing action merges so closely into the work done by rotating cutters in the so-called "milling"-machine that, as regards results, each one must be considered in comparison with all the others. But the milling-machine (and, indeed, the grinding-ma chine) is now an instrument of precision and worthy of being ranked with machine-tools. We shall first consider the file and the rasp, or primitive hand-tools, and secondly the hone and the grindstone because they are used to sharpen edge-tools, and shall incidentally treat the grindstone as a shaping device as well as an appliance. for sharpening.