The usual shapes of all punches are conical, and the angle subtended by two opposite sides should be about six or seven degrees. The outlines of the transverse sections of punches do not differ so much from each other as the sections of drifts, the only two general forms for punches being circular and rectangular, termed round and square. Round ones are used for piercing holes into nuts, joint-bosses, rings that are to be forged without a joint, spanners, and many other classes of ordinary work; also for making flat-bottomed recesses into iron or steel previous to punching smaller holes at the centres of the flat-bottomed recesses, the shapes of the smaller holes being either round or square. Square punches are required for square bolt-holes, key-ways, also rectangular gaps in the ends of rods or bars. In this case, the square hole is first punched at a proper distance from the extremity, and the superfluous piece afterwards cut out with chiselling. Square punches are useful also for making many other rectangular openings in thin bars and plates.

Four-sided punches for making small holes are made ten or twelve inches long, for the convenience of holding the punch with one hand while the other hand is employed to drive the punch through or partly through the work. Large punches that require a sledge or steam-hammer are made of the shortest possible length that is sufficient, that the hammering may not bend the punch to any considerable extent. A short square punch is represented in Fig. 212. Whether the punch is round or square, a short one requires an iron-wire handle, twisted around the punch, instead of a wood handle ; an iron handle, being thin, will allow a great length of the punch to be driven into the hole during the hammering for punching.

Punches small or large, long or short, require to be made of the best tough, hard, cast steel. When such metal is accessible, the only hardening that the tool requires is given when it has been driven into the work and become nearly or quite red-hot; at such times, the punch is put into water in a bucket provided for the purpose.