A common form of tool for turning wrought iron and steel is the diamond point, shown in Fig. 124. The name is derived from the shape of the top face. This tool has both front and side rake, which form a keen edge without reducing the strength. It is used for finishing only when the point is ground slightly rounding. In finishing, but little metal should be removed and a fine feed used.
The feed of a tool is the amount of longitudinal advance at each revolution of the work.
For roughing out cast iron, a strong and rapid working tool is a round nose with considerable side rake. For finishing wrought iron and steel, a modification of the diamond point, as shown in Fig. 125, is often used. For cast iron, a square-nosed tool, Fig. 126, may be used. The square-nosed tool must be carefully ground and accurately set; otherwise it is very likely to gouge into the softer parts of the metal. When finishing wrought iron and steel, the tool should be liberally supplied with oil or soda water. Cast iron, on the other hand, is usually worked dry, both in roughing out and in finishing.
Fig. 125. Tool for Finishing Wrought Iron and Steel.
Fig. 126. Tool for Finishing Cast Iron.