Drills, reamers, boring bars, counter-bores, etc., may have shanks formed upon them, or may fit in collets fitted to the tool-holes in the turret, or in plain drill-holders. A split collet is shown in Fig. 300; and a plain drill-holder, in Fig. 301.

Taps and dies may be held in the releasing holder shown in Fig. 302. The shell A is fitted to the tool-hole in the turret, through which the shank of the holder B passes and is permitted to revolve freely, except when the two are locked together by the pins CC when pressure is applied against the face of the die-holder, or by the pin D when pressure is exerted in the opposite direction. In the medium position, both pins are inoperative. This permits right- and left-hand dies to be used, the machine being reversed at the proper moment.

Fig. 302. Releasing Holder.

Fig. 303 shows a simple form of box tool, in which A is the shank entering the tool-hole in the turret; BB are the cutting tools, adjusted by the screws bb; and CC are the jaws of the backrest device adjusted to the diameter of the turned portion of the work by the screws cc. Of the two tools, the leading one is for roughing, and the other for finishing.

Fig. 303. Simple Box Tool.

In the box tool shown in Fig. 304, the two tools BB are adjustable with relation to each other; hence two shoulders may be turned upon a piece of work simultaneously, at a required. distance apart. One box tool may make the roughing cuts, and in the next tool-hole may be a similar box tool with its tools set to make the finishing cuts. The backrest jaw C is also adjustable, so as to keep it directly back of the leading tool. If the box tool is so constructed as to have the tools BB at a considerable distance apart, two back-rest jaws may be necessary, being set in the slots shown.

Fig. 304. Double Box Tool.

Fig. 305. Simple Tool Clamp.

Fig. 305 shows a simple form of tool clamp in which a variety of tools having square or rectangular shanks, such as inside boring tools, may be clamped, thus enabling the operator to use ordinary lathe tools for many simple jobs.

Fig. 306. Turret Holder for Tool-Post.

Fig. 306 shows a turret-holder for a tool-post B, adapted to tools similar in form and purpose to those of Fig. 304, but with greater rigidity, as the shank A is secured in the tool-hole, and the cap screws CC hold it rigidly to the face of the turret. Fig. 307 shows a well-designed box-tool device, providing for two tools and four back-rest jaws, all adjustable in any direction that may be necessary. At

Fig. 307. Box Tool Holder for Two Tools and Four Back-Rest Jaws.

A is the shank to be entered in the tool hole in the turret; BB are the two tools; and CCCC are the four back-rest jaws.

The large tools that are bolted to the faces of the turret will be shown in the engravings illustrating turret-lathe operations.

In Fig. 308 is shown a well-designed form of cross-slide, carrying two tools very rigidly secured and capable of adjustment in all directions horizontally; the tools may also be inclined. The base A supports the two tool-blocks carrying the tools BB. The base A may be moved transversely across the lathe-bed by means of the hand-wheel C, which is a very steady and well-controlled movement suitable for broad-faced forming tools or for facing tools; for narrow or cutting-off tools, recourse is had to the rack-and-pinion device operated much more rapidly by the lever D.

Fig. 308. Cross-Slide Carrying Two Tools.

The tools held in the tool-holders (commonly called box tools), in tool-posts, or in the various styles of tool-holders for the cross-slide, and in many of the special tool-holders of fixtures, are usually short pieces cut from a square or rectangular bar of tool steel of suitable dimensions for the work and the holding fixture. They are roughly shaped at the cutting point, hardened, and then ground to the form desired. In using what is commonly known as high-speed steel for these tools, short pieces are broken from the bar; and the proper forms for the cutting point or edge are obtained by grinding, no forging operation being necessary. While the forms usually used in lathe tools are also used in this class of cutting tools, there are many others, the particular form of work to be done determining their shape.