Machinery's Handbook, 31st Edition
Taps 1005 Table 24a. Taper Pipe Thread Limits (Ground and Cut Thread: Ground Thread For NPS, NPTF, and ANPT; Cut Thread for NPT only) ANSI/ASME B94.9-2008 (R2018)
Reference Dimensions
Taper per Inch on Diameter a Cut Thread Ground Thread
Gage Measurement
Tolerance ±
Tap Drill Size NPT, ANPT, NPTF d
Nominal Size
Threads per Inch
Cut Thread
Ground Thread Min. Max. Min. Max.
L 1 , Length c
Projection Inch b
1 ⁄ 16
27 27 18 18 14
0.312 0.0625 0.0625 0.0599 0.0703 0.0599 0.0651 0.1600 0.312 0.0625 0.0625 0.0599 0.0703 0.0599 0.0651 0.1615 0.459 0.0625 0.0625 0.0599 0.0703 0.0599 0.0651 0.2278 0.454 0.0625 0.0625 0.0599 0.0703 0.0599 0.0651 0.2400 0.579 0.0625 0.0625 0.0599 0.0677 0.0599 0.0651 0.3200 0.565 0.0625 0.0625 0.0599 0.0677 0.0599 0.0651 0.3390 0.678 0.0937 0.0937 0.0599 0.0677 0.0599 0.0651 0.4000 0.686 0.0937 0.0937 0.0599 0.0677 0.0599 0.0651 0.4200 0.699 0.0937 0.0937 0.0599 0.0677 0.0599 0.0651 0.4200 0.667 0.0937 0.0937 0.0599 0.0677 0.0599 0.0651 0.4360 0.925 0.0937 0.0937 0.0612 0.0664 0.0612 0.0651 0.6820 0.925 0.0937 0.0937 0.0612 0.0664 0.0612 0.0651 0.7660
C Q
1 ⁄ 8 1 ⁄ 4 3 ⁄ 8 1 ⁄ 2 3 ⁄ 4
7 ⁄ 9 ⁄
16 16
45 ⁄ 29 ⁄
64 32
11.5 11.5 11.5 11.5
1
1 9 ⁄ 64
1 1 ⁄ 4 1 1 ⁄ 2
1 31 ⁄ 1 23 ⁄
64 32
2
8 8
2 3 ⁄ 16
2 1 ⁄ 2
2 39 ⁄
64
3
20
3 15 ⁄ 16
a Taper is 0.0625 inch per 1.000 inch on diameter (1:16) ( 3 ⁄ b Distance, small end of tap projects through L
4 inch per 12 inches).
1 taper ring gage.
c Dimension, L 1 , thickness on thin ring gage; see ANSI/ASME B1.20.1 and B1.20.5. d Given sizes permit direct tapping without reaming the hole, but only give full threads for approximate L 1 distance. All dimensions are given in inches. Lead Tolerance: ± 0.003 inch per inch on cut thread, and ± 0.0005 inch per inch on ground thread. Angle Tolerance: ± 40 min. in half angle and 60 min. in full angle for 8 cut threads per inch; ± 45 min. in half angle and 68 min. in full angle for 11 1 ⁄ 2 to 27 cut threads per inch; ± 25 min. in half angle for 8 ground threads per inch; and ± 30 min. in half angle for 11 1 ⁄ 2 to 27 ground threads per inch. Table 24b. Taper Pipe Thread — Widths of Flats at Tap Crests and Roots for Cut Thread NPT and Ground Thread NPT, ANPT, and NPTF ANSI/ASME B94.9-2008 (R2018)
Column I
Column II
Ground Thread a
NPT—Cut and Ground Thread a ANPT—Ground Thread a
Threads per Inch
Tap Flat Width at
NPTF Min. b 0.0040
Min. b 0.0014
Max.
Max.
Major diameter Minor diameter Major diameter Minor diameter Major diameter Minor diameter Major diameter Minor diameter Major diameter Minor diameter
0.0041 0.0041 0.0057 0.0057 0.0064 0.0064 0.0073 0.0073 0.0090 0.0090
0.0055 0.0040 0.0065 0.0050 0.0065 0.0050 0.0083 0.0060 0.0103
27
…
…
0.0021
0.0050
18
…
…
0.0027
0.0050
14
…
…
0.0033
0.0060
11 1 ⁄ 2
…
…
0.0048
0.0080
8
… 0.0080 a Cut thread taps made to Column I are marked NPT but are not recommended for ANPT applications. Ground thread taps made to Column I are marked NPT and may be used for NPT and ANPT applications. Ground thread taps made to Column II are marked NPTF and used for dryseal application. b Minimum minor diameter flats are not specified and may be as sharp as practicable. All dimensions are given in inches. …
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