Fig. 174 shows the different shapes of tools ordinarily used in lathe work. These are made of high-carbon steel, or preferably of self-hardening alloy steel for heavy work. The cutting ends are forged, hardened, tempered and ground. They are designated as follows:

Fig. 174. - Lathe Tools.

(1-2) Left and right-hand side-tools.

(3-7) Bent and straight cut-off tools.

(4-5) Right and left-hand diamond points.

(6) Fillet or round-nose tool.

(8) Threading tool.

(9) Bent threading tool.

(10) Roughing tool.

(11) Inside boring tool.

(12) Inside threading tool.

The diamond-point tools, Nos. 4 and 5, are about superseded by a round-nosed tool shown in Fig. 175 which is superior for size of chip, resistance to wear, and smoothness of cut, particularly on heavy work. This tool shows its advantages best when made of high-speed steel.

Because of the high cost of alloy steels used for tools, much expense is saved by having merely a cutting end of alloy steel held in a tool holder. These holders are in many styles to suit the shape of the cutting end.

Fig. 175. - Round-Nose Tool.

Many special tools are devised for use in turret lathes, as these lathes do special work and do not use the ordinary lathe tools.