Table 13a. Straight and Taper Pipe Tap Dimensions (Ground and Cut Thread) ANSI/ASME B94.9-2008 (R2018)
Ground Thread
Cut Thread Only
Number of Flutes
Length Optional Neck, I 1
NPSC, NPSM, NPSF
Inter rupted Thread
NPT, NPTF, ANPT
Nominal Size, Inch a
Length Overall, L
Thread Length, I
Square Length, I 2
Shank Diameter, d 1
Size of Square, a
Regular Thread
NPSC, NPSM
Threads per Inch
NPT
27 27 27 18 18 14 14 11 11
4 4 4 4 4 4 5 5 5 7 7 8 8
…
2.13 2.13 2.13 2.44 2.56 3.13 3.25 3.75 4.00 4.25 4.25 5.50 6.00
0.69 0.75 0.75 1.06 1.06 1.38 1.38 1.75 1.75 1.75 1.75 2.56 2.63
0.38 0.38 0.38 0.44 0.50 0.63 0.69 0.81 0.94 1.00 1.13 1.25 1.38
0.3125 0.234 0.3125 0.234 0.4375 0.328 0.5625 0.421 0.7000 0.531 0.6875 0.515 0.9063 0.679 1.1250 0.843 1.3125 0.984 1.5000 1.125 1.8750 1.406 2.2500 1.687 2.6250 1.968
0.375
… … …
b
1 ⁄
16
5 5 5 5 5 5 5 5 7 7
…
…
b, c b, c b, c b, c b, c b, c b, c b, c b, i b, i
d, e d, e d, e d, e d, e
f, g, h f, g, h f, g, h f, g, h f, g, h f, g, h f, g, h f, g, h
1 ⁄ 1 ⁄ 1 ⁄ 3 ⁄ 1 ⁄ 3 ⁄
8 8 4 8 2 4
0.375 0.375 0.375
a a a a a a a
… … … … … …
d d
1
11 1 ⁄
2 2 2 2
… … …
1 1 ⁄ 1 1 ⁄
1 ⁄ 1 ⁄
4 2
… … … …
f, h f, h
2
11 1 ⁄
8 8
… …
… … … … … …
2 1 ⁄
h h
2
3
a Pipe taps 1 ⁄
8 inch are furnished with large-size shanks unless the small shank is specified.
b High-speed ground thread 1 ⁄
16 to 2 inches including noninterrupted (NPT, NPTF, and ANPT). 8 to 1 1 ⁄ 4 inch including interrupted (NPT, NPTF, and ANPT). 8 to 1 inch including noninterrupted (NPSC and NPSM). 8 to 1 inch including noninterrupted (NPSC and NPSM).
c High-speed ground thread 1 ⁄
d High-speed ground thread 1 ⁄ e High-speed cut thread 1 ⁄ g High-speed cut thread 1 ⁄ h Carbon cut thread 1 ⁄ 8 to 1 f High-speed cut thread 1 ⁄
8 to 1 inch including noninterrupted (NPT).
8 to 1
1 ⁄ 4 inch including interrupted (NPT).
1 ⁄ 4 inch including interrupted (NPT).
i High-speed ground thread 1 1 ⁄
2 to 2 inches including interrupted (NPT).
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