Taper Pipe Taps
Taper Pipe Taps Ground Thread (USCTI Table 338) American National Standard Taper Pipe Thread Form (NPT) Aeromautical National Taper Pipe Thread Form (ANPT) Dryseal American National Standard Taper Pipe Thread Form (NPTF)
Thread Limits
Width of Flats - Taps
*Gage Measurement (Inch)
Taper per Foot (Inch)
Width of Flats at Tap Crest and Roots NPT NPTF Min. Max. Min. Max.
Nominal Size (Inch)
Threads per Inch NPT
Threads Per Inch
Element
Tolerance (+/-)
Projection
Min.
Max.
1/16
27 27 18 18 14 14
0.312 0.312 0.459 0.454 0.579 0.565 0.678 0.686 0.699 0.667 0.925 0.925 0.938 0.950
1/16 1/16 1/16 1/16 1/16 1/16 3/32 3/32 3/32 3/32 3/32 3/32
23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 23/32 25/32 47/64 25/32 47/64 25/32 47/64 25/32 47/64 25/32
Major Dia. Minor Dia. Major Dia. Minor Dia. Major Dia. Minor Dia. Major Dia. Minor Dia. Major Dia. Minor Dia.
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 0.0030
27
0.0014
0.0040
1/8 1/4 3/8 1/2 3/4
18
0.0021
0.0050
14
0.0027
0.0050
1
11-1/2 11-1/2 11-1/2 11-1/2
11 1/2
0.0033
0.0060
1 1/4 1 1/2
8
0.0048
0.0080
2
2 1/2
8 8 8 8
Minimum minor diameter flats are not specified. May be as sharp as practicable. Ground Thread Taps marked NPT may be used for NPT and ANPT applications.
3
3 1/2
1/8 1/8
4
*Distance small end of tap projects through an L1 American Standard Taper Pipe Thread Ring Gage (See Table 357 page 780).
LEAD TOLERANCE A maximum lead deviation of ±.0005” within any two threads not farther apart than one inch is permitted. FORMULA FOR AMERICAN NATIONAL STANDARD PIPE FORM
Angle Tolerance
Minimum major diameter = Measured pitch diameter +A. Maximum major diameter = Measured pitch diameter +B. Minimum minor diameter = Measured pitch diameter -B. Maximum minor diameter = Measured pitch diameter -C. FORMULA FOR DRYSEAL AMERICAN NATIONAL STANDARD PIPE FORM Minimum major diameter = Measured pitch diameter +D. Maximum major diameter = Measured pitch diameter +E. Minimum minor diameter = Maximum or smaller. Maximum minor diameter = Measured pitch diameter -E.
Threads Per Inch
Tolerance Half Angle
8
±25’ ±30’
11-1/2 to 27 inclusive
Formula Values
Threads Per Inch
A
B
C
D
E
27 18 14
0.0267 0.0296 0.0257 0.0234 0.0251 0.0408 0.0444 0.0401 0.0377 0.0395 0.0535 0.0571 0.0525 0.0515 0.0533 0.0658 0.0696 0.0647 0.0614 0.0649
11 1/2
8
0.0966 0.1000 0.0946
–
–
For essential dimensions of American National Standard Pipe Threads (See Table 357 page 780). Ground Thread American Standard Pipe Form Taps made to this table are to be marked NPT. Ground Thread Dryseal American National Standard Pipe Taps made to this table are to be marked NPTF. Ground Thread Taps, Aeronautical National Thread Form, made to this table are marked ANPT.
Threading Technical
777
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