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Internal ACME Thread General Purpose Size Chart

The following table defines recommended industry standard sizes for Internal ACME General Purpose Threads per American National Standard ASME/ANSI B1.5. All dimensional data is given in inches.

Designation
Size Decimal
TPI
Tol. Class
Minor Dia.
Pitch Dia.
Major Dia.
Tap Drill
Min.
Max.
Min.
Max.
Min.
Max.
1/4-16 ACME
0.25
16
2G
0.1875
0.1925
0.2188
0.2293
0.2600
0.2700
0.1875
1/4-16 ACME
0.25
16
3G
0.1875
0.1925
0.2188
0.2237
0.2600
0.2700
0.1875
1/4-16 ACME
0.25
16
4G
0.1875
0.1925
0.2188
0.2223
0.2600
0.2700
0.1875
1/4-16 ACME
0.25
16
5G
0.1875
0.1925
0.2188
0.2216
0.2600
0.2700
0.1875
5/16-14 ACME
0.3125
14
2G
0.2411
0.2461
0.2768
0.2882
0.3225
0.3325
0.2411
5/16-14 ACME
0.3125
14
3G
0.2411
0.2461
0.2768
0.2821
0.3225
0.3325
0.2411
5/16-14 ACME
0.3125
14
4G
0.2411
0.2461
0.2768
0.2806
0.3225
0.3325
0.2411
5/16-14 ACME
0.3125
14
5G
0.2411
0.2461
0.2768
0.2798
0.3225
0.3325
0.2411
3/8-12 ACME
0.375
12
2G
0.2917
0.2967
0.3333
0.3456
0.3850
0.3950
0.2917
3/8-12 ACME
0.375
12
3G
0.2917
0.2967
0.3333
0.3391
0.3850
0.3950
0.2917
3/8-12 ACME
0.375
12
4G
0.2917
0.2967
0.3333
0.3374
0.3850
0.3950
0.2917
3/8-12 ACME
0.375
12
5G
0.2917
0.2967
0.3333
0.3366
0.3850
0.3950
0.2917
7/16-12 ACME
0.4375
12
2G
0.3542
0.3592
0.3958
0.4084
0.4475
0.4575
0.3542
7/16-12 ACME
0.4375
12
3G
0.3542
0.3592
0.3958
0.4017
0.4475
0.4575
0.3542
7/16-12 ACME
0.4375
12
4G
0.3542
0.3592
0.3958
0.4000
0.4475
0.4575
0.3542
7/16-12 ACME
0.4375
12
5G
0.3542
0.3592
0.3958
0.3992
0.4475
0.4575
0.3542
1/2-10 ACME
0.5
10
2G
0.4000
0.4050
0.4500
0.4637
0.52
0.5400
0.4000
1/2-10 ACME
0.5
10
3G
0.4000
0.4050
0.4500
0.4564
0.52
0.5400
0.4000
1/2-10 ACME
0.5
10
4G
0.4000
0.4050
0.4500
0.4546
0.52
0.5400
0.4000
1/2-10 ACME
0.5
10
5G
0.4000
0.4050
0.4500
0.4537
0.52
0.5400
0.4000
5/8-8 ACME
0.625
8
2G
0.5000
0.5062
0.5625
0.5779
0.645
0.6650
0.5000
5/8-8 ACME
0.625
8
3G
0.5000
0.5062
0.5625
0.5697
0.645
0.6650
0.5000
5/8-8 ACME
0.625
8
4G
0.5000
0.5062
0.5625
0.5676
0.645
0.6650
0.5000
5/8-8 ACME
0.625
8
5G
0.5000
0.5062
0.5625
0.5666
0.645
0.6650
0.5000
3/4-6 ACME
0.75
6
2G
0.5833
0.5916
0.6667
0.6841
0.77
0.7900
0.5833
3/4-6 ACME
0.75
6
3G
0.5833
0.5916
0.6667
0.6748
0.77
0.7900
0.5833
3/4-6 ACME
0.75
6
4G
0.5833
0.5916
0.6667
0.6725
0.77
0.7900
0.5833
3/4-6 ACME
0.75
6
5G
0.5833
0.5916
0.6667
0.6714
0.77
0.7900
0.5833
7/8-6 ACME
0.875
6
2G
0.7083
0.7166
0.7917
0.8096
0.895
0.9150
0.7083
7/8-6 ACME
0.875
6
3G
0.7083
0.7166
0.7917
0.8000
0.895
0.9150
0.7083
7/8-6 ACME
0.875
6
4G
0.7083
0.7166
0.7917
0.7977
0.895
0.9150
0.7083
7/8-6 ACME
0.875
6
5G
0.7083
0.7166
0.7917
0.7965
0.895
0.9150
0.7083
1-5 ACME
1
5
2G
0.8000
0.8100
0.9000
0.9194
1.02
1.0400
0.8000
1-5 ACME
1
5
3G
0.8000
0.8100
0.9000
0.9091
1.02
1.0400
0.8000
1-5 ACME
1
5
4G
0.8000
0.8100
0.9000
0.9065
1.02
1.0400
0.8000
1-5 ACME
1
5
5G
0.8000
0.8100
0.9000
0.9052
1.02
1.0400
0.8000
1 1/8-5 ACME
1.125
5
2G
0.9250
0.9350
1.0250
1.0448
1.145
1.165
0.9250
1 1/8-5 ACME
1.125
5
3G
0.9250
0.9350
1.0250
1.0342
1.145
1.165
0.9250
1 1/8-5 ACME
1.125
5
4G
0.9250
0.9350
1.0250
1.0316
1.145
1.165
0.9250
1 1/8-5 ACME
1.125
5
5G
0.9250
0.9350
1.0250
1.0303
1.145
1.165
0.9250
1 1/4-5 ACME
1.25
5
2G
1.0500
1.0600
1.1500
1.1701
1.27
1.29
1.0500
1 1/4-5 ACME
1.25
5
3G
1.0500
1.0600
1.1500
1.1594
1.27
1.29
1.0500
1 1/4-5 ACME
1.25
5
4G
1.0500
1.0600
1.1500
1.1567
1.27
1.29
1.0500
1 1/4-5 ACME
1.25
4
5G
1.0500
1.0600
1.1500
1.1554
1.27
1.29
1.0500
1 3/8-4 ACME
1.375
4
2G
1.1250
1.1375
1.2500
1.2720
1.395
1.415
1.1250
1 3/8-4 ACME
1.375
4
3G
1.1250
1.1375
1.2500
1.2603
1.395
1.415
1.1250
1 3/8-4 ACME
1.375
4
4G
1.1250
1.1375
1.2500
1.2573
1.395
1.415
1.1250
1 3/8-4 ACME
1.375
4
5G
1.1250
1.1375
1.2500
1.2559
1.395
1.415
1.1250
1 1/2-4 ACME
1.5
4
2G
1.2500
1.2625
1.3750
1.3973
1.52
1.54
1.2500
1 1/2-4 ACME
1.5
4
3G
1.2500
1.2625
1.3750
1.3854
1.52
1.54
1.2500
1 1/2-4 ACME
1.5
4
4G
1.2500
1.2625
1.3750
1.3824
1.52
1.54
1.2500
1 1/2-4 ACME
1.5
4
5G
1.2500
1.2625
1.3750
1.3810
1.52
1.54
1.2500
1 3/4-4 ACME
1.75
4
2G
1.5000
1.5125
1.6250
1.6479
1.77
1.79
1.5000
1 3/4-4 ACME
1.75
4
3G
1.5000
1.5125
1.6250
1.6357
1.77
1.79
1.5000
1 3/4-4 ACME
1.75
4
4G
1.5000
1.5125
1.6250
1.6326
1.77
1.79
1.5000
1 3/4-4 ACME
1.75
4
5G
1.5000
1.5125
1.6250
1.6311
1.77
1.79
1.5000
2-4 ACME
2
4
2G
1.7500
1.7625
1.8750
1.8985
2.02
2.04
1.7500
2-4 ACME
2
4
3G
1.7500
1.7625
1.8750
1.8860
2.02
2.04
1.7500
2-4 ACME
2
4
4G
1.7500
1.7625
1.8750
1.8828
2.02
2.04
1.7500
2-4 ACME
2
4
5G
1.7500
1.7625
1.8750
1.8813
2.02
2.04
1.7500
2 1/4-3 ACME
2.25
3
2G
1.9167
1.9334
2.0833
2.1096
2.27
2.29
1.9167
2 1/4-3 ACME
2.25
3
3G
1.9167
1.9334
2.0833
2.0956
2.27
2.29
1.9167
2 1/4-3 ACME
2.25
3
4G
1.9167
1.9334
2.0833
2.0921
2.27
2.29
1.9167
2 1/4-3 ACME
2.25
3
5G
1.9167
1.9334
2.0833
2.0903
2.27
2.29
1.9167
2 1/2-3 ACME
2.5
3
2G
2.1667
2.1834
2.3333
2.3601
2.52
2.54
2.1667
2 1/2-3 ACME
2.5
3
3G
2.1667
2.1834
2.3333
2.3458
2.52
2.54
2.1667
2 1/2-3 ACME
2.5
3
4G
2.1667
2.1834
2.3333
2.3422
2.52
2.54
2.1667
2 1/2-3 ACME
2.5
3
5G
2.1667
2.1834
2.3333
2.3404
2.52
2.54
2.1667
2 3/4-3 ACME
2.75
3
2G
2.4169
2.4334
2.5833
2.6106
2.77
2.79
2.4169
2 3/4-3 ACME
2.75
3
3G
2.4169
2.4334
2.5833
2.5960
2.77
2.79
2.4169
2 3/4-3 ACME
2.75
3
4G
2.4169
2.4334
2.5833
2.5924
2.77
2.79
2.4169
2 3/4-3 ACME
2.75
3
5G
2.4169
2.4334
2.5833
2.5906
2.77
2.79
2.4169
3-2 ACME
3
2
2G
2.5000
2.5250
2.7500
2.7816
3.02
3.04
2.5000
3-2 ACME
3
2
3G
2.5000
2.5250
2.7500
2.7647
3.02
3.04
2.5000
3-2 ACME
3
2
4G
2.5000
2.5250
2.7500
2.7605
3.02
3.04
2.5000
3-2 ACME
3
2
5G
2.5000
2.5250
2.7500
2.7584
3.02
3.04
2.5000
3 1/2-2 ACME
3.5
2
2G
3.0000
3.0250
3.2500
3.2824
3.52
3.54
3.0000
3 1/2-2 ACME
3.5
2
3G
3.0000
3.0250
3.2500
3.2651
3.52
3.54
3.0000
3 1/2-2 ACME
3.5
2
4G
3.0000
3.0250
3.2500
3.2608
3.52
3.54
3.0000
3 1/2-2 ACME
3.5
2
5G
3.0000
3.0250
3.2500
3.2587
3.52
3.54
3.0000
4-2 ACME
4
2
2G
3.5000
3.5250
3.7500
3.7832
4.02
4.04
3.5000
4-2 ACME
4
2
3G
3.5000
3.5250
3.7500
3.7655
4.02
4.04
3.5000
4-2 ACME
4
2
4G
3.5000
3.5250
3.7500
3.7611
4.02
4.04
3.5000
4-2 ACME
4
2
5G
3.5000
3.5250
3.7500
3.7589
4.02
4.04
3.5000
4 1/2-2 ACME
4.5
2
2G
4.0000
4.0250
4.2500
4.2839
4.52
4.54
4.0000
4 1/2-2 ACME
4.5
2
3G
4.0000
4.0250
4.2500
4.2658
4.52
4.54
4.0000
4 1/2-2 ACME
4.5
2
4G
4.0000
4.0250
4.2500
4.2613
4.52
4.54
4.0000
4 1/2-2 ACME
4.5
2
5G
4.0000
4.0250
4.2500
4.2591
4.52
4.54
4.0000
5-2 ACME
5
2
2G
4.5000
4.5250
4.7500
4.7846
5.02
5.04
4.5000
5-2 ACME
5
2
3G
4.5000
4.5250
4.7500
4.7662
5.02
5.04
4.5000
5-2 ACME
5
2
4G
4.5000
4.5250
4.7500
4.7615
5.02
5.04
4.5000
5-2 ACME
5
2
5G
4.5000
4.5250
4.7500
4.7592
5.02
5.04
4.5000

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