assume the form in B, the stream of sand directed on the backs sharpening them up to a keen edge, which is stronger than the ordinary cut shape. There are two styles of cutting, the single, or float, c, and the double, D. The single is used chiefly by lathe-workers, woodworkers, and in sawmills, the double in all classes of metal-working. Rasps have their teeth formed by a punch, which leaves a series of single teeth upstanding, as at E. Each of these styles is made in six different cuts, the single in Rough, Middle, Bastard, Second Cut, Smooth, Dead Smooth, the double similarly; and the rasps in Horse, Rough, Middle, Bastard, Second Cut, Smooth. These differences relate to the size of the teeth and their pitching.

In Fig. 2, we have the next great difference in files, that of their cross sections, which occur in a number of sizes for each shape. The rectangular cross sections are shown first, the

square, A, the pillar, B, which is a thick pattern of flat file; the flat, c, a thinner proportioned style; and when of small dimensions a pottance file; the mill, D, thinner than the flat; the warding, E, thinner still (in proportion to width). The swaged reaper files, F and G, differ in the form of their edges. Two styles used for sawmill work are the mill, H, and the topping, J. A file having tapered faces is the reaper, K. Triangular shapes are the three-square, L, the cant file; M and the knife, N. A combination of two friangles is the feather-edge, or slitting, 0. Files derived from the circle are the round, P. the pitsaw, or frame saw, Q, the half-round, , the cabinet, s, the crossing, T, and the tumbler, Ewo or three modifications based on these shapes are sometimes made. A safe-edge file is one in which one or more edges are left smooth,

parallel, or tapering to various degrees. In Fig. 3, A is a parallel or blunt file, of equal cross section throughout. A dead parallel file is one that is machined truly before being cut. An equalling file has a very slight amount of belly or curvature lengthwise. A tapered file, B, is either made with straight sides, or bellied as shown. The square file is tapered, c, while the three-square or triangular is both parallel, D, and tapered, E, as is also the rat-tail, F, and round, G. The semi-curved patterns are tapered, H, or parallel, J. Knife reapers have a handle forged on, K. Rifflers, L, have a handle formed in the middle portion, and curved file parts at the ends. Rasps are made in the

file is controlled more easily when a hand is placed at each end than when both are gripping the handle (as must be done in filing blank-ended slots, &c.). In filing such work as keys, truth. is more easily secured by making sweeping side or rather diagonal strokes, which make a flatter face and also remove material more effectively. The direction of stroke may be changed frequently, so that the lines cross, and the ridges are topped off with less effort. For slogging work a large coarse file should be used, working it right from shank to tip.

same shapes, excepting that one, the horse, is parallel down its length, and minus any tang or handle.

For the majority of work the ordinary file handle is suitable, but when the hand must be raised up to clear the surface being operated on, some device has to be adopted, either that of cranking the tang, or fitting a special handle over it to embrace the tang, and press on the top face of the file.

Filing. The chief difficulty in filing is that of endeavouring to counteract the tendency of the hands to move in arcs from the shoulder joints, which prevents the file from taking a straight course. Narrow surfaces are more troublesome to finish flat than broad ones; a

Pressure should only be given on the forward stroke, that on the back being released, otherwise the points of the teeth will be snapped off. New files should never be used on rough castings or forgings, but the skin should either be removed first with an older file, or the work should be pickled in acid. Brass or gun-metal should be the first metal on which a new file is used, followed by cast iron, and then wrought iron and steel; a file which still works satisfactorily on wrought iron will not cut brass rapidly enough. Oil or chalk are used on files to make them finish rather more smoothly, and to diminish "pinning," or clogging of the teeth with particles of metal, which are especially troublesome in fibrous metals. When these get in, they may either be brushed out with card-wire, or if stuck tight, picked out with a piece of pointed wire.

"Draw-filing" is a method of finishing accurately, by grasping the file ends and moving the tool up and down, with its body lying at right angles to the axis of the work, the resulting surface being perfectly flat, and the marks running straight longitudinally. For keys, force-fit shafts, and other such work, this is a suitable method to pursue. In filing hollow curves, care must be taken not to simply push the tool forward, or grooves and ridges will