thus giving it all the ordinary movements given to a lathe-tool, with the additional circular ones.

The tool, as shown in the drawing, consists of the cast-iron base, having a tongue which fits the T-slot of the tool-block, and is firmly held thereon by the bolts shown. A cap is fastened to the base by counterbored screws, while projections upon it and a groove in the base serve to locate the cap. The worm-gear,

FIG. 344.

having trunnions integral with it, is journaled in the extension or wings of the base and cap. Meshing with the worm-gear is the worm, the shaft of which is journaled by the base and cap and extends toward the front of the lathe, where it terminates in the hand-wheel at a convenient length. An oblong slot is cut in the worm-gear to receive the turning-tool, which is fastened by the central set-screw.

As moulds and dies are usually made in halves, it is not often required to turn out more than this, but proper proportioning of the fixture allows as much as two-thirds of the sphere to be turned out. The device, of course, will turn out moulds for circular rings as well as for balls by simply setting it out from the line of centres to the required radius.

CHAPTER XXI.

Special Tools, Fixtures, Devices, Arrangements, Contrivances, and Novel Methods for Metal-Working.

THE DEVISING AND CONSTRUCTING OF SPECIAL

TOOLS.

WHILE the constructing of the regular types and standard classes of tools necessitates skill, accuracy, judgment, and experi ence on the part of the tool-maker, it is in the devising of special means for the rapid and economical production of special work that his ingenuity is utilized. The ability to devise special tools for special work is one to be prized, and should always be eucouraged and developed. In this chapter are illustrations and descriptions of a large variety of special tools, fixtures, devices, arrangements, and novel methods for metal-working; by making himself familiar with them the mechanic will find no difficulty in devising means for the rapid production of any special part; while the descriptions of the proper ways to make them will show how to avoid all unnecessary expense and labor.

A SET OF TOOLS FOR MACHINING A CAM.

The illustrations show a set of tools for machining a repetition casting of unusual shape, which was used as a cam on an automatic machine for making fruit-baskets, and, as some of the tools are of a novel and improved design, a slight description of them will suggest their use for other work.

The casting machined is shown in Fig. 345. It is, to say the least, a rather difficult piece to machine, because of the irregular cam surface. This cam surface was required to be finished very accurately and so that the castings, when finished, would interchange perfectly. The other portions of the casting to be machined so as to interchange were the boring and reaming of the

hole A, the facing of the hub at G, of the sides C, and the finishing of the conical surface at D. The hub B was left rough.

The number of operations required to finish the casting was three-the first being done in the turret-lathe and the other two

in the engine-lathe. The first operation consisted of boring the hole A and reaming it, facing the hub G, and machining and finishing the conical surface D. The tools used in this operation

are shown in Figs. 346 to 350. Fig. 346 is a combination boring and hub-facing tool used to bore the hole A and face the hub G at the same time. It consists of a long stem H, with the cutter

W

R

FIG. 347.

I in a slot in the end held by the taper-pin J, and the hub-facing tool-holder K, which is located on the bar by the set-screw L, the point of which screws into a milled channel in the cutterbar, as shown at Q. The hub-facing cutter N is held in position

by the two set-screws N N. in the turret-lathe.

P is the usual split bushing as used

This

For reaming the hole A the reamer Fig. 357 is used. reamer consists of the body Q, of tool steel, and six cutters or blades T. These blades are let into inclined channels, as shown by the dotted lines at U U, to allow the readjustment after being worn, or after grinding. The blades are held by taper-headed screws W which are let into the centres of the narrow-sawed slots V. By tightening these screws the metal is forced tightly against the blades, thus holding them securely.

Fig. 348 shows the tool used for roughing off the conical surface S. The tool has three cutting-points K and is gradually

slid along under the surface by the hand-lever, the shank of the tool being held in the tool-post. This surface was finished by a flat-bladed tool of sufficient width to take the entire line at once.

The second operation, facing the two sides C C, thus sizing the width of the cam face, is done in the lathe by the special double-facing tool, Fig. 349. Three castings are located on an

arbor at once and fastened by a nut. The tool is held in the tool-post in the usual way.

The last operation, machining the cam surface, was the most difficult. It also was done in the lathe with four special fixtures. These were: A special slide-rest for the cutting-tool, a special

FIG. 349.

cross-slide for the lathe, a combined master-cam and chuck, and a locating- and supporting-stud for the work. These fixtures, in position on the lathe with the work, are shown in Figs. 350 and

Roller

M

FIG. 350.

351. The master-cam and chuck was a forging, which was first fitted to the spindle of the lathe, after which the chuck portion was finished with an internal conical surface at II as a locating point for the conical surface D D of the work. The cam portion was then laid out and finished on the universal milling-machine.