Machinery's Handbook, 31st Edition
1836
SELF-THREADING SCREWS Table 2. ANSI Standard Threads and Points for Thread Cutting Self-Tapping Screws ANSI/ASME B18.6.3-2013
L
L
S P
S P
d
d
D
D
Type BF
Flat Width
Slight Radius Permissible
L
S
d
P
60°
D
Detail of Thread Form
Type BT
L
L
L
S
S P
S P
P
D
D
D
Type D
Type F
L
L
S
S
P
P
D
D
Type C
Type T
See Table 5 and Table 7 for thread data. Cross Recesses.— Type I cross recess has a large center opening, tapered wings, and blunt bottom, with all edges relieved or rounded. Type IA cross recess has a large center open ing, wide straight wings, and blunt bottom, with all edges relieved or rounded. Type II con sists of two intersecting slots with parallel sides converging to a slightly truncated apex at the bottom of the recess. Type III has a square center opening, slightly tapered side walls, and a conical bottom, with top edges relieved or rounded.
Table 3. ANSI Standard Cross Recesses for Self-Tapping Screws ANSI/ASME B18.6.3-2013 and Metric Thread Forming and Thread Cutting Tapping Screws ANSI/ASME B18.6.5M-2000 (Withdrawn)
M
M
M
M
N
N
N
TYPE I
TYPE II
TYPE III
TYPE IA
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