It is usual, however, to chamfer off the half threads at the ends of the dies, because if left of their full height they are apt to break off when in use.
"Modern Machine-Shop Practice, Volumes I and II"
Joshua Rose
It is sometimes the practice, however, to chamfer off the first two threads on one side of the dies, leaving the teeth on the other side full, and to use the chamfered as the leading side in all cases in which the thread on the work does not require to be cut up to a shoulder, but turning the dies over with the full threaded teeth as the leading ones when the thread does require to be carried up to a head or shoulder on the work.
"Modern Machine-Shop Practice, Volumes I and II"
Joshua Rose
For example, the chamfer at A may be ground farther towards B, and still leave in action sufficient teeth to equal in width of chaser the diameter of the bolt.
"Modern Machine-Shop Practice, Volumes I and II"
Joshua Rose