The Jack Plane
This plane has the cutting edge of its blade ground so it is slightly curved (Fig. 6), because, as the bit must be driven out so it will take a deep bite into the rough surface of the wood, the curved cutting edge prevents the corner edges of the bit from digging into the planed surface.
On the other hand, the bits of the smoothing and finishing planes are ground straight across their cutting edges. In the foregoing we have not enumerated the different special planes, designed to make beads, rabbets, tongues and grooves, but each type is fully illustrated, so that an idea may be obtained of their characteristics. (Fig. 6a