A method of producing cams without a lathe especially adopted for the purpose is shown in [Figs. 1270] and [1272], which are extracted from Mechanics. The apparatus consists of a frame e, which fits on the cross ways of an ordinary lathe. The cross-feed screw is removed, so that e may slide backwards and forthwards freely. The frame e carries the worm-wheel a and the worm-gear b, which is operated by the crank f. The cam c to be cut is bolted on to the face of the worm-wheel, which faces the headstock of the lathe. The form for the cam, which may be made of sheet steel, or thicker material, according to the wear it is to have, is fastened to the face of the cam.
Fig. 1271.
Fig. 1272.
A cutter, like a fluted reamer, such as is shown in [Fig. 1271], is then put in the live centre of the lathe. Care must be taken that the shank is the same size as the fluted part, and that the flutes are not cut up farther than the thickness that the cam grooves are to be cut in the blank. Having attached a cord to the back of e, pass it over a pulley h, fastened on the rear of the lathe, and hang on a weight g. [Fig. 1272] is an edge view of the device, looking from the back of the lathe. It shows the worm a, blank c, and former d all bolted together, while the cutter i is ready in its place on a line with the centre of the worm, and just at back of the former. The machine is operated by turning the crank f, which causes the worm a, also c and d, to revolve slowly, while the cutter i has a rather rapid rotation. The weight causes the cutter to be held firmly against the form f, and to follow its curves in and out.
