Fig. 179.
[Wheel Cutting in the Lathe.]
Among the various uses to which a lathe may be put, wheel-cutting is one of the most important, so many pieces of mechanism requiring cogged wheels of various pitches and forms of tooth. By the aid of the slide rest such an apparatus as figured may be readily arranged, and the work rapidly and accurately performed. The guide by which the cogs and spaces are determined is the division plate already alluded to, and which is not visible in the present drawing, but the index of which is shown at G. C is the cutter frame with a side pulley (one on each side) to conduct the catgut band from the revolving spindle to the overhead motion on to the flywheel. The spindle carries a pulley for the cord and a cutter wheel, I, to which an exceedingly rapid evolution is given. There are many patterns of these wheels, the edges of which, cut into teeth like a fine saw or file, are the exact form of the spaces required between the cogs; hence, some are rectangular, some have a triangular section. The thicker the wheel to be cut the larger should be the cutter, so that the bottom of the cut may be virtually level. In [Fig. 181] another form of cutter is shown, which if put into sufficiently rapid motion answers as well, if not better, than the wheel-shaped cutters. It is a simple short bar of hard steel, with the edges bevelled in alternate directions, fitted into a slot in the spindle and held by a wedge or screw. The shape of the end is as before, a cross section of the space between two teeth. The cutter frame is here arranged to fit into the ordinary tool-holder of the slide rest, but the form may, of course, be varied at pleasure. It will be noticed that the slide rest, as delineated here, is different to that of which details have been given. It is made without the sole, and fits into the socket of an ordinary rest. Thus it can be turned on a centre, and becomes, to all intents and purposes, a compound slide rest. It is on this plan the small ornamental turning rest of lighter construction is made. The spindle fitting the socket projects from the centre of the lowest frame, and is cast in one piece with it. If the apparatus is compactly and strongly made, it becomes a very serviceable form, and is much used for the small lathes in sea-going steamers. The sides are made very short, so that the extent of traverse is small. We may here mention an addition to the rest socket, enabling the workman to raise this kind, or that used with drills and cutters, which is simple and convenient. Inside the iron socket a few turns of a screw are cut, and a second socket of brass with an outside thread is made to fit into it Figs. [182 A and B], the latter being a section. The edge of the inside socket is sometimes milled round, to facilitate holding it by the thumb and finger. In this way the height of the slide rest, or tee of the common rest, is adjustable to a great nicety.
Figs. 180, 181.
Fig. 182.