The common firmer chisel (Fig. 140), the bevel-backed firmer chisel (Fig. 141), and the heavy firmer chisel (Fig. 142) represent the general types of hand chisels suitable for elementary woodwork. Where but one style can be had the first is preferred. Either style may have either tanged blades, as shown in Figs. 140 and 141, or socket blades, as shown in Fig. 142. The tanged blades are better for small hands and for light work.

Keep the chisels sharp. The angle of the basil side should be as small as possible to not break when in use. This angle can be determined only by experiment for each person and for the various kinds of wood. The cutting edge should usually be straight and the basil a smooth, even surface, as shown in Fig. 143.

When the chisel is sharpened on the oil stone, a new angle is formed, as shown by the line B in Fig. 143. This angle also varies with the nature of the tool and work. For soft wood the angle is smaller than for hard wood, and usually each time the chisel is sharpened on the oilstone the end will become more blunt until it is necessary to change the angle by grinding the tool on the grindstone.

Fig. 140. Plain Tanged Firmer Chisel.

Fig. 141. Bevel Tanged Firmer Chisel.

Fig I42. Socket Firmer Chisel.

In whetting the chisel hold it firmly as in whetting the plane, Fig. 175. Move it back and forth so that the angle produced will be even and flat. The common mistake in whetting chisels and planes is to make the end rounding as shown at C, instead of a true flat surface, Fig. 143. Should a wire edge develop it may be necessary to reverse the chisel, as shown in Fig. 144, and holding it firmly and flat on the oilstone move it forward, breaking off the wire edge. It may be necessary to change from the first to the second position several times before the wire edge will be removed. After using the oilstone the edge may be yet further improved by using a leather strop, as shown in Fig. 202.

Fig. 144. Removing a Wire Edge.

Fig. 143. Chisel Basil. A, Angle at which the chisel is ground. B, Angle at which the chisel is whet. C, In-correct shape caused by carelessness in whetting or grinding.

One side of the chisel should be kept perfectly flat to the cutting edge so that it may rest firmly against the surface of the part being worked, as in Figs. 39, 40, 43, 53, 73, etc. Should this side become rounding, either from wear or from carelessness in whetting or stroping, the end must be ground off on the grindstone until the surface is straight.

For directions about grinding chisels, see what is said about the grindstone and its use.