TAP THREAD LIMIT STANDARDS AND DIMENSIONS

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Table 338 - Taper Pipe Taps

Nominal Size Inches Threads Per Inch
*Gage Measurement — Inches
Taper Per Foot — Inches

Tolerance Plus or Minus Cut Thread Ground Thread

Projection Cut Thread Ground Thread Min. Max. Min. Max.

1/16
1/8
1/4
3/8
1/2 27
27
18
18
14 .312
.312
.459
.454
.579 1/16
1/16
1/16
1/16
1/16 1/16
1/16
1/16
1/16
1/16 23/32
23/32
23/32
23/32
23/32 27/32
27/32
27/32
27/32
13/16 23/32
23/32
23/32
23/32
23/32 25/32
25/32
25/32
25/32
25/32

3/4
1
1 1/4
1 1/2
2 14
11 1/2
11 1/2
11 1/2
11 1/2 .565
.678
.686
.699
.667 1/16
3/32
3/32
3/32
3/32 1/16
3/32
3/32
3/32
3/32 23/32
23/32
23/32
23/32
23/32 13/16
13/16
13/16
13/16
13/16 23/32
23/32
23/32
23/32
23/32 25/32
25/32
25/32
25/32
25/32

2 1/2
3
3 1/2
4
8
8
8
8
.925
.925
.938
.950
3/32
3/32
1/8
1/8
3/32
3/32
1/8
1/8
47/64
47/64
47/64
47/64
51/64
51/64
51/64
51/64
47/64
47/64
47/64
47/64
25/32
25/32
25/32
25/32

*Distance small end of tap projects through (L.) Taper Ring Gage

Table 335 - Straight Pipe Taps

Nominal Size Inches Threads Per Inch NPS
Major Diameter
Pitch Diameter

Plug at Gaging Notch Minimum G Maximum H Plug at Gaging Notch E Minimum K Maximum L

1/8
1/4
3/8
1/2
3/4 27
18
18
14
14 .3983
.5286
.6640
.8260
1.0364 .4022
.5340
.6694
.8335
1.0440 .4032
.5350
.6704
.8345
1.0450 .3736
.4916
.6270
.7784
.9889 .3746
.4926
.6280
.7794
.9899 .3751
.4931
.6285
.7799
.9904

1
1 1/4
1 1/2
2
2 1/2 11 1/2
11 1/2
11 1/2
11 1/2
8 1.2966
1.6413
1.8803
2.3542
2.8454 1.3057
1.6505
1.8894
2.3634
2.8597 1.3072
1.6520
1.8909
2.3649
2.8612 1.2386
1.5834
1.8223
2.2963
2.7622 1.2397
1.5845
1.8234
2.2974
2.7633 1.2407
1.5855
1.8244
2.2984
2.7646

3
3 1/2
4
8
8
8
3.4718
3.9721
4.4704
3.4860
3.9863
4.4846
3.4875
3.9878
4.4861
3.3885
3.8888
4.3871
3.3896
3.8899
4.3882
3.3909
3.8912
4.3895

Table 335A - Straight Pipe Taps — Dryseal

Nominal Size Inches Threads Per Inch NPS
Major Diameter
Pitch Diameter
Minor* Diameter Flat Maximum

Minimum G Maximum H Plug at Gaging Notch E Minimum K Maximum L

1/16
1/8
1/4
3/8
1/2 27
27
18
18
14 .3008
.3932
.5239
.6593
.8230 .3018
.3942
.5249
.6603
.8240 .2812
.3736
.4916
.6270
.7784 .2772
.3696
.4859
.6213
.7712 .2777
.3701
.4864
.6218
.7717 .004
.004
.005
.005
.005

3/4
1 14
11 1/2 1.0335
1.2933 1.0345
1.2943 .9889
1.2386 .9817
1.2295 .9822
1.2305 .005
.006

*As specified or sharper.

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