INTERNAL ACME THREAD DIMENSIONS CHART


Internal ACME thread dimensions are given in the following chart per ASME/ANSI B1.5 standard for general purpose single-start ACME threads. Tolerance classes for ACME threads are 2G, 3G, and 4G and 2G is the preferred tolerance class. ACME thread angle is 29°.

Tolerances Of Acme Screw Thread
Allowances, Tolerances, and Clearances for General Purpose Single-start Acme Threads (All Classes)



ACME Thread
Designation
Nominal
Size
Threads
/in.
Tol.
Class
Minor
Diameter
Pitch
Diameter
Major
Diameter
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
3G 0.2237
4G 0.2223
5/16-14 ACME 0.3125 14 2G 0.2411 0.2461 0.2768 0.2882 0.3225 0.3325
3G 0.2821
4G 0.2806
3/8-12 ACME 0.375 12 2G 0.2917 0.2967 0.3333 0.3456 0.3850 0.3950
3G 0.3391
4G 0.3374
7/16-12 ACME 0.4375 12 2G 0.3542 0.3592 0.3958 0.4084 0.4475 0.4575
3G 0.4017
4G 0.4000
1/2-10 ACME 0.5 10 2G 0.4000 0.4050 0.4500 0.4637 0.5200 0.5400
3G 0.4564
4G 0.4546
5/8-8 ACME 0.625 8 2G 0.5000 0.5062 0.5625 0.5779 0.6450 0.6650
3G 0.5697
4G 0.5676
3/4-6 ACME 0.75 6 2G 0.5833 0.5916 0.6667 0.6841 0.7700 0.7900
3G 0.6748
4G 0.6725
7/8-6 ACME 0.875 6 2G 0.7083 0.7166 0.7917 0.8096 0.8950 0.9150
3G 0.8000
4G 0.7977
1-5 ACME 1 5 2G 0.8000 0.8100 0.9000 0.9194 1.0200 1.0400
3G 0.9091
4G 0.9065
1 1/8-5 ACME 1.125 5 2G 0.9250 0.9350 1.0250 1.0448 1.1450 1.1650
3G 1.0342
4G 1.0316
1 1/4-5 ACME 1.25 5 2G 1.0500 1.0600 1.1500 1.1701 1.2700 1.2900
3G 1.1594
4G 1.1567
1 3/8-4 ACME 1.375 4 2G 1.1250 1.1375 1.2500 1.2720 1.3950 1.4150
3G 1.2603
4G 1.2573
1 1/2-4 ACME 1.5 4 2G 1.2500 1.2625 1.3750 1.3973 1.5200 1.5400
3G 1.3854
4G 1.3824
1 3/4 ACME 1.75 4 2G 1.5000 1.5125 1.6250 1.6479 1.7700 1.7900
3G 1.6357
4G 1.6326
2-4 ACME 2 4 2G 1.7500 1.7625 1.8750 1.8985 2.0200 2.0400
3G 1.8860
4G 1.8828
2 1/4-3 ACME 2.25 3 2G 1.9167 1.9334 2.0833 2.1096 2.2700 2.2900
3G 2.0956
4G 2.0921
2 1/2-3 ACME 2.5 3 2G 2.1667 2.1834 2.3333 2.3601 2.5200 2.5400
3G 2.3458
4G 2.3422
2 3/4-3 ACME 2.75 3 2G 2.4167 2.4334 2.5833 2.6106 2.7700 2.7900
3G 2.5960
4G 2.5924
3-2 ACME 3 2 2G 2.5000 2.5250 2.7500 2.7816 3.0200 3.0400
3G 2.7647
4G 2.7605
3 1/2-2 ACME 3.5 2 2G 3.0000 3.0250 3.2500 3.2824 3.5200 3.5400
3G 3.2651
4G 3.2608
4-2 ACME 4 2 2G 3.5000 3.5250 3.7500 3.7832 4.0200 4.0400
3G 3.7655
4G 3.7611
4 1/2-2 ACME 4.5 2 2G 4.0000 4.0250 4.2500 4.2839 4.5200 4.5400
3G 4.2658
4G 4.2613
5-2 ACME 5 2 2G 4.5000 4.5200 4.7500 4.7846 5.0200 5.0400
3G 4.7662
4G 4.7615

Tap drill hole for ACME thread , drill selection shall be done to obtain a finished hole somewhere between maximum and minimum minor diameters. It shall be considered to be close to the maximum minor diameter to reduce the amount of material to be removed when tapping the thread.


Definitions:


Design Profile: The shapes of the external and internal threads in which the limits of dimensions are applied. The thread form of General Purpose Acme Thread is given in the following figure.

General Purpose Acme Thread Form
General Purpose Acme Thread Form

Major Diameter: The maximum diameter of a thread which is diameter of the crest of a male thread or root of a female thread.

Minor Diameter: The minimum diameter of a thread which is diameter of the root of a male thread or crest of a female thread.

Thread class: A classification system to classify the threads for interchangeability and manufacturability.

Threads per inch: Number of full thread per an inch length.


Supplements:


Link Usage
Acme Thread Dimensions Calculator Calculator form of the ACME thread dimensions chart.
External ACME Thread Dimensions Chart Tabulated form of the ACME thread dimensions calculator.

Reference:

  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2016) . Machinery's Handbook . 30th edition.  Industrial Press Inc.
  • Oberg, E. , Jones ,F.D. , Horton H.L. , Ryffel H.H., (2012) . Machinery's Handbook . 29th edition.  Industrial Press Inc.
  • ASME B1.5-1997, Acme Screw Threads