Taps: Straight Pipe Taps
TABLE 335-STRAIGHT PIPE TAPS
Ground Threads
American National Standard Straight Pipe Thread Form
(NPS) (NPSC) (NPSM)
THREAD LIMITS
Major Diameter
Nominal Threads
Plug
at Min.
Per
Sizes
Max.
Inch Gaging
Inches
H
G
Notch
1/8
1/4
3/8
1/2
3/4
1
1 1/4
1 1/2
2
2 1/2
3
3 1/2
4
27
18
18
14
14
11-1/2
11-1/2
11-1/2
11-1/2
8
8
8
8
0.3983
0.5286
0.6640
0.8260
1.0364
1.2966
1.6413
1.8803
2.3542
2.8454
3.4718
3.9721
4.4704
0.4022
0.5347
0.6701
0.8347
1.0447
1.3062
1.6507
1.8897
2.3639
2.8604
3.4868
3.9872
4.4855
0.4032
0.5357
0.6711
0.8357
1.0457
1.3077
1.6522
1.8912
2.3654
2.8619
3.4883
3.9887
4.4870
Pitch Diameter
Plug at
Gaging Min. Max.
K
L
Notch
E
0.3736 0.3746 0.3751
0.4916 0.4933 0.4938
0.6270 0.6287 0.6292
0.7784 0.7806 0.7811
0.9889 0.9906 0.9916
1.2386 1.2402 1.2412
1.5834 1.5847 1.5862
1.8223 1.8237 1.8252
2.2963 2.2979 2.2994
2.7622 2.7640 2.7660
3.3885 3.3904 3.3924
3.8888 3.8908 3.8928
4.3871 4.3891 4.3911
ANGLE TOLERANCE
Threads Per Inch
Deviation In Half Angle
8
11 1/2 to 27 Inclusive
25' plus or minus
30' plus or minus
FORMULA FOR AMERICAN NATIONAL
STANDARD PIPE FORM (NPS)
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, A 107,
Col. D.
Minor Diameter
Major Diameter
Nominal
Sizes
Inches
1/8
1/4 to 3/4 incl.
1 to 4 incl.
Max.
H
K + A -- 0.0010
K + A -- 0.0020
K + A -- 0.0021
Min.
G
H -- 0.0010
H -- 0.0010
H -- 0.0015
Max.
M -- B
M -- B
M -- B
Note: Taps made to these specifications are marked NPS and used
for NPS, NPSC and NPSM.
TABLE 335-A-STRAIGHT PIPE TAPS
Ground Thread
American National Standard Straight Dryseal
Pipe Thread Form (NPSF)
1/16
1/8
1/4
3/8
1/2
3/4
1
27
27
18
18
14
14
11-1/2
Major Diameter
Plug at
Min.
Max. Gaging
Notch
G
H
E
0.3008 0.3018 0.2812
0.3932 0.3942 0.3736
0.5239 0.5249 0.4916
0.6593 0.6603 0.6270
0.8230 0.8240 0.7784
1.0335 1.0345 0.9889
1.2933 1.2943 1.2386
27
18
14
11 1/2
8
0.0296
0.0444
0.0571
0.0696
0.1000
0.0257
0.0401
0.0525
0.0647
0.0946
Actual
measured
pitch
diameter
FORMULA FOR AMERICAN NATIONAL
STANDARD DRYSEAL PIPE FORM (NPSF)
Major Diameter
THREAD LIMITS
Nominal Threads
Per
Sizes
Inch
Inches
NPSF
Threads
Per Inch
Pitch Diameter
Minor*
Min.
Max. Diam.
Flat
K
L
Max.
0.2772 0.2777 0.004
0.3696 0.3701 0.004
0.4859 0.4864 0.005
0.6213 0.6218 0.005
0.7712 0.7717 0.005
0.9817 0.9822 0.005
1.2295 1.2305 0.006
*As specified or sharper.
NOTE: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.
Tap Technical
FORMULA VALUES
LEAD TOLERANCE
A maximum lead deviation of plus or minus .0005" within any two
threads not farther apart than one inch is permitted.
Pitch Diameter
Nominal
Sizes
Inches
Min.
G
Max.
H
Min.
K
Max.
L
Max.
Minor
Diam.
1/6
1/8
1/4
3/8
1/2
3/4
1
H -- 0.0010
H -- 0.0010
H -- 0.0010
H -- 0.0010
H -- 0.0010
H -- 0.0010
H -- 0.0010
K + Q -- 0.0005
K + Q -- 0.0005
K + Q -- 0.0005
K + Q -- 0.0005
K + Q -- 0.0005
K + Q -- 0.0005
K + Q -- 0.0001
L -- 0.0005
L -- 0.0005
L -- 0.0005
L -- 0.0005
L -- 0.0005
L -- 0.0005
L -- 0.0010
E -- F
E -- F
E -- F
E -- F
E -- F
E -- F
E -- F
M -- Q
M -- Q
M -- Q
M -- Q
M -- Q
M -- Q
M -- Q
FORMULA VALUES
Threads
Per Inch
27
18
14
11 1/2
Pitch diameter
of plug
at gaging
notch
0.0035
0.0052
0.0067
0.0081
Actual
measured
pitch
diameter
0.0251
0.0395
0.0533
0.0649
ANGLE TOLERANCE
Threads Per Inch
11 1/2 to 27 inclusive
Deviation in Half Angles
30' plus or minus
WWW.OSGTOOL.COM
LEAD TOLERANCE
A maximum lead deviation of plus or minus .0005" within any
two threads not farther apart than one inch is permitted.
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