USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 2/TASK 2
AMERICAN STANDARD AND DRY SEAL PIPE THREADS.
(a) Diameter and Pitch of Tapped Hole. The coarser the pitch, the larger
is the thread depth if a full thread were cut.
Try a drill giving 75
percent thread depth first.
If tap breakage results, reduce the thread
depth gradually by using larger drills until satisfactory performance is
A nut with only 50 percent thread depth will break the
bolt before it strips the thread.
American Standard screw threads (Table I on page 182) are standardized in
two series, coarse and fine. As a tap size becomes smaller, the percentage
of double thread depth in relation to basic major diameter of the screw
generally becomes larger.