By careless sharpening an extra bevel is sometimes formed, as shown at b.
The cutting angle is then no sharper than if the chisel were shaped like that shown by dotted lines, and care must always be taken when sharpening to keep the line cd straight, so that angle a will be the real cutting angle.
Two classes of chisels are in common use: the framing chisel used for heavy work, such as the frames of buildings; and the firmer chisel. The framing chisel is strong and heavy, and has a handle capable of withstanding the blows of a mallet. The firmer chisel is designed for finer and lighter work without the mallet.
Fig. 30. The Framing Chisel
Fig. 31. The Firmer Chisel
Fig. 32. Proper Position for Horizontal Chiseling