Fig. 1014.
Fig. 1015.
The sides of the tool from a to b must be inclined to the body of the tool steel, as shown in [Fig. 1014], the degree of the inclination depending upon the pitch of thread to be cut. It may be determined, however, by the means shown in [Fig. 1015].
Draw the line a, and at a right angle to it line b, whose length must equal the circumference of the thread to be cut and measured at its root. On the line a set off from b the pitch of thread to be cut as at c, then draw the diagonal d, which will represent the angle of the bottom of the thread to the work axis, and the angle of the tool sides must be sufficiently greater to give the necessary clearance. The width of the point c of the tool should be made sufficiently less than the width of the thread groove to permit of the sides of the thread being pinched (after the thread is cut to depth) with a tool such as was shown in [Fig. 968].
Fig. 1016.