THREADING
TOOLS
S O M T A P 1 2 C A T A L O G U E
184
Tap Terminology
BASIC FORM OF ISO METRIC
AND UNIFIED THREAD FORMS
H
= 0.86603 x P
H/4
= 0.21651 x P
H/8
= 0.10825 x P
3/8 H = 0.32476 x P
5/8 H = 0.54127 x P
BASIC FORM OF
WHITWORTH THREAD
H
= 0.96049 x P
h
= 2/3 H = 0.64033 x P
H/6
= 0.16008 x P
r
= 0.13733 x P
BASIC FORM OF
BA THREAD
H
= 1.13630 x P
h
= 0.60000 x P
r
= 0.18083 x P
s
= 0.26817 x P
5/8 H
H
H/8
H/4
P/2
P/8
3/8 H
P/4
60°
H/6
H/6
H h
P
r
r
55°
BASIC THREAD FORMS
H h
s
s
P
r
47½°
