Straight Pipe Taps
Straight Pipe Taps Ground Thread (USCTI Table 335) American National Standard Straight Pipe Thread Form (NPS) (NPSC) (NPSM)
Thread Limits
Angle Tolerance
Major Diameter
Pitch Diameter
Threads Per Inch
Deviation in Half Angle
Nominal Sizes (inch)
8
± 25' ± 30'
Plug at Gaging Notch E
Threads Per Inch
Plug at Gaging Notch
Min. K
Max. L
Min. G
Max. H
11 1/2 to 27 Incl.
The maximum Pitch Diameter of tap is based upon an allowance deducted from the maximum product pitch diameter of NPSC or NPSM, whichever is smaller. The minimum Pitch Diameter of tap is derived by subtracting the ground thread pitch diameter tolerance for actual equivalent size as shown in Table 331, page 771, Col. D. Formula for American National Standard Dryseal Pipe Form (NPS)
1/8 1/4 3/8 1/2 3/4
27 0.3983 0.4022 0.4032 0.3736 0.3746 0.3751 18 0.5286 0.5347 0.5357 0.4916 0.4933 0.4938 18 0.6640 0.6701 0.6711 0.6270 0.6287 0.6292 14 0.8260 0.8347 0.8357 0.7784 0.7806 0.7811 14 1.0364 1.0447 1.0457 0.9889 0.9906 0.9916 11-1/2 1.2966 1.3062 1.3077 1.2386 1.2402 1.2412 11-1/2 1.6413 1.6507 1.6522 1.5834 1.5847 1.5862 11-1/2 1.8803 0.1890 1.8912 1.8223 1.8237 1.8252 11-1/2 2.3542 2.3639 2.3654 2.2963 2.2979 2.2994 8 2.8454 2.8604 2.8619 2.7622 2.7640 2.7660 8 3.4718 3.4868 3.4883 3.3885 3.3904 3.3924 8 3.9721 3.9872 3.9887 3.8888 3.8908 3.8928 8 4.4704 4.4855 4.4870 4.3871 4.3891 4.3911
1
1-1/4 1-1/2
Major Diameter
Minor Diameter
2
Nominal Size (inch)
2-1/2
Min. G
Max. H
Max.
3
3-1/2
1/8
H - 0.0010 K + A - 0.0010 H - 0.0010 K + A - 0.0020 H - 0.0015 K + A - 0.0021
M - B M - B M - B
4
1/4 to 3/4 Incl.
1 to 4 Incl.
LEAD TOLERANCE A maximum lead deviation of plus of minus 0.0005” within any two threads not farther apart than one inch is permitted. Note: Taps made to these specifications are marked NPS and used for NPS, NPSC, and NPSM.
Formula Values
Threads Per Inch
A
B
M
27 18 14
0.0296 0.0444 0.0571 0.0696 0.1000
0.0257 0.0401 0.0525 0.0647 0.0946
Actual
Measured
Pitch
11-1/2
Diameter
8
Straight Pipe Taps Ground Thread (USCTI Table 335-A) American National Standard Straight Dryseal Pipe Thread Form (NPSF)
Formula for American National Standard Dryseal Pipe Form (NPSF)
Thread Limits
Major Diameter
Pitch Diameter
Major Diameter
Pitch Diameter
*As specified or sharper. The major diameter of standard taper pipe plug gages and the minor diameter of standard taper pipe ring gages used for gaging dryseal threads will be truncated .20p minimum to .25p maximum for all pitches. Minor* Diam. Flat Max. 1/16 27 0.3008 0.3018 0.2812 0.2772 0.2777 0.004 1/8 27 0.3932 0.3942 0.3736 0.3696 0.3701 0.004 1/4 18 0.5239 0.5249 0.4916 0.4859 0.4864 0.005 3/8 18 0.6593 0.6603 0.6270 0.6213 0.6218 0.005 1/2 14 0.8230 0.8240 0.7784 0.7712 0.7717 0.005 3/4 14 1.0335 1.0345 0.9889 0.9817 0.9822 0.005 1 11-1/2 1.2933 1.2943 1.2386 1.2295 1.2305 0.006 Nominal Size (inch) Threads Per Inch Min. G Max. H Plug at Gaging Notch E Min. K Max. L
Max. Minor Diam.
Nominal Size (inch)
Min. G
Max. H
Min. K
Max. L
1/6 H - 0.0010 K + Q - 0.0005 L - 0.0005 E - F M - Q 1/8 H - 0.0010 K + Q - 0.0005 L - 0.0005 E - F M - Q 1/4 H - 0.0010 K + Q - 0.0005 L - 0.0005 E - F M - Q 3/8 H - 0.0010 K + Q - 0.0005 L - 0.0005 E - F M - Q 1/2 H - 0.0010 K + Q - 0.0005 L - 0.0005 E - F M - Q 3/4 H - 0.0010 K + Q - 0.0005 L - 0.0005 E - F M - Q 1 H - 0.0010 K + Q - 0.0001 L - 0.0010 E - F M - Q
Formula Values
Threads Per Inch
E
F
M
Q
Angle Tolerance
27 18 14
Pitch Diameter
0.0035 Actual
0.0251
of plug
0.0052 Measured 0.0395
Threads Per Inch 11-1/2 to 27 Incl.
Deviation in Half Angles
at gaging
0.0067
Pitch 0.0533
± 30'
11-1/2
notch
0.0081 Diameter
0.0649
LEAD TOLERANCE A maximum lead deviation of ±0.0005” within any two threads not farther apart than one inch is permitted.
Threading Technical
779
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