When cutting the threads of a taper tap, Fig. 109, it is necessary to use a lathe having a taper attachment, as the pitch of the threads is not correct if the taper is obtained by setting over the tailstock. Like machine taps, the teeth of a taper tap must be relieved back of the cutting edge. In setting the threading too! for cutting taper taps, care should be taken that it is square with the axis of the tap, rather than square with the taper sides.

Fig. 109. Typical Taper Tap.

Courtesty of Wiley and Russell Manufacturing Company, Greenfield, Massachusetts.