LatheCalculator

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Thread calculator

Choose a thread form and size to get the basic dimensions for cutting it on the lathe. The numbers come from each standard’s basic-profile formula, not copied tables, and the working is shown so you can check them.

Safety: screw-cutting needs full attention. Know how you will stop or disengage at the shoulder before you start, never reach over a turning chuck, and keep the leadscrew guard in place.
How it works, guides and notes

Using the results

External threads: turn the blank to the major diameter, or a few thou under for a free fit. Set the top slide to half the thread angle (29.5° for 60° threads is the usual British practice; 27° for Whitworth) and feed in to the stated depth. Finish to a nut or ring gauge, not to the number alone.

Internal threads: bore or drill to the internal minor diameter (for tapping, see the tap drill finder).

Worked example, M10 × 1.5: pitch dia d2 = 10 − 0.6495 × 1.5 = 9.026 mm. External minor d3 = 10 − 1.2269 × 1.5 = 8.160 mm. Depth h3 = 0.6134 × 1.5 = 0.920 mm. Tap drill = 10 − 1.5 = 8.5 mm.

Forms covered

  • ISO metric and UNC/UNF share the same 60° basic profile (ISO 68-1 / ASME B1.1).
  • BSW, BSF, ME and BSP use the 55° Whitworth form with rounded crests and roots. ME is the Model Engineer series at a constant 32 or 40 TPI.
  • BA is a 47.5° form where pitch = 0.9ⁿ mm (BS 93).
  • Acme (29°, see the Acme table) and Trapezoidal (30°) are lead-screw forms with flat crests and roots.

Basic sizes only. Tolerance classes (6g/6H, 2A/2B, etc.) put real parts slightly under (external) or over (internal) these values. Some BSW, BSF and ME size lists here were compiled from memory and are being checked against BS 84. They are marked est. until confirmed.

Acme thread table, 1/4" to 3"

General-purpose Acme (29°) dimensions for each nominal size. The standard TPI for each size is marked std. Other rows are common alternative pitches from leadscrew makers (EST: check your supplier stocks them). Pick a size and TPI above for the working, or scroll the table sideways on a phone. Switch to Detailed mode to see every column.

SizeTPIPitchMajor diaPitch diaMinor dia (screw)Thread depthTool tip widthCrest flat (basic)Root flat (screw)Nut major diaNut bore-to (minor)
1/4"16 std0.0625"
1.587 mm		0.2500"
6.350 mm		0.2188"
5.556 mm		0.1775"
4.508 mm		0.0362"
0.921 mm		0.0219"
0.556 mm		0.0232"
0.588 mm		0.0219"
0.556 mm		0.2600"
6.604 mm		0.1875"
4.762 mm
1/4"10 EST0.1000"
2.540 mm		0.2500"
6.350 mm		0.2000"
5.080 mm		0.1300"
3.302 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.2700"
6.858 mm		0.1500"
3.810 mm
1/4"12 EST0.0833"
2.117 mm		0.2500"
6.350 mm		0.2083"
5.292 mm		0.1567"
3.979 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.2600"
6.604 mm		0.1667"
4.233 mm
1/4"20 EST0.0500"
1.270 mm		0.2500"
6.350 mm		0.2250"
5.715 mm		0.1900"
4.826 mm		0.0300"
0.762 mm		0.0172"
0.438 mm		0.0185"
0.471 mm		0.0172"
0.438 mm		0.2600"
6.604 mm		0.2000"
5.080 mm
5/16"14 std0.0714"
1.814 mm		0.3125"
7.938 mm		0.2768"
7.030 mm		0.2311"
5.869 mm		0.0407"
1.034 mm		0.0252"
0.640 mm		0.0265"
0.673 mm		0.0252"
0.640 mm		0.3225"
8.191 mm		0.2411"
6.123 mm
5/16"10 EST0.1000"
2.540 mm		0.3125"
7.938 mm		0.2625"
6.667 mm		0.1925"
4.889 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.3325"
8.445 mm		0.2125"
5.397 mm
5/16"12 EST0.0833"
2.117 mm		0.3125"
7.938 mm		0.2708"
6.879 mm		0.2192"
5.567 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.3225"
8.191 mm		0.2292"
5.821 mm
3/8"12 std0.0833"
2.117 mm		0.3750"
9.525 mm		0.3333"
8.467 mm		0.2817"
7.154 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.3850"
9.779 mm		0.2917"
7.408 mm
3/8"8 EST0.1250"
3.175 mm		0.3750"
9.525 mm		0.3125"
7.938 mm		0.2300"
5.842 mm		0.0725"
1.841 mm		0.0437"
1.111 mm		0.0463"
1.177 mm		0.0437"
1.111 mm		0.3950"
10.033 mm		0.2500"
6.350 mm
3/8"10 EST0.1000"
2.540 mm		0.3750"
9.525 mm		0.3250"
8.255 mm		0.2550"
6.477 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.3950"
10.033 mm		0.2750"
6.985 mm
7/16"12 std0.0833"
2.117 mm		0.4375"
11.112 mm		0.3958"
10.054 mm		0.3442"
8.742 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.4475"
11.367 mm		0.3542"
8.996 mm
7/16"10 EST0.1000"
2.540 mm		0.4375"
11.112 mm		0.3875"
9.842 mm		0.3175"
8.064 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.4575"
11.620 mm		0.3375"
8.572 mm
1/2"10 std0.1000"
2.540 mm		0.5000"
12.700 mm		0.4500"
11.430 mm		0.3800"
9.652 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.5200"
13.208 mm		0.4000"
10.160 mm
1/2"8 EST0.1250"
3.175 mm		0.5000"
12.700 mm		0.4375"
11.112 mm		0.3550"
9.017 mm		0.0725"
1.841 mm		0.0437"
1.111 mm		0.0463"
1.177 mm		0.0437"
1.111 mm		0.5200"
13.208 mm		0.3750"
9.525 mm
1/2"12 EST0.0833"
2.117 mm		0.5000"
12.700 mm		0.4583"
11.642 mm		0.4067"
10.329 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.5100"
12.954 mm		0.4167"
10.583 mm
5/8"8 std0.1250"
3.175 mm		0.6250"
15.875 mm		0.5625"
14.287 mm		0.4800"
12.192 mm		0.0725"
1.841 mm		0.0437"
1.111 mm		0.0463"
1.177 mm		0.0437"
1.111 mm		0.6450"
16.383 mm		0.5000"
12.700 mm
5/8"5 EST0.2000"
5.080 mm		0.6250"
15.875 mm		0.5250"
13.335 mm		0.4050"
10.287 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		0.6450"
16.383 mm		0.4250"
10.795 mm
5/8"6 EST0.1667"
4.233 mm		0.6250"
15.875 mm		0.5417"
13.758 mm		0.4383"
11.134 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		0.6450"
16.383 mm		0.4583"
11.642 mm
5/8"10 EST0.1000"
2.540 mm		0.6250"
15.875 mm		0.5750"
14.605 mm		0.5050"
12.827 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.6450"
16.383 mm		0.5250"
13.335 mm
5/8"12 EST0.0833"
2.117 mm		0.6250"
15.875 mm		0.5833"
14.817 mm		0.5317"
13.504 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.6350"
16.129 mm		0.5417"
13.758 mm
3/4"6 std0.1667"
4.233 mm		0.7500"
19.050 mm		0.6667"
16.933 mm		0.5633"
14.309 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		0.7700"
19.558 mm		0.5833"
14.817 mm
3/4"5 EST0.2000"
5.080 mm		0.7500"
19.050 mm		0.6500"
16.510 mm		0.5300"
13.462 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		0.7700"
19.558 mm		0.5500"
13.970 mm
3/4"8 EST0.1250"
3.175 mm		0.7500"
19.050 mm		0.6875"
17.462 mm		0.6050"
15.367 mm		0.0725"
1.841 mm		0.0437"
1.111 mm		0.0463"
1.177 mm		0.0437"
1.111 mm		0.7700"
19.558 mm		0.6250"
15.875 mm
3/4"10 EST0.1000"
2.540 mm		0.7500"
19.050 mm		0.7000"
17.780 mm		0.6300"
16.002 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.7700"
19.558 mm		0.6500"
16.510 mm
3/4"12 EST0.0833"
2.117 mm		0.7500"
19.050 mm		0.7083"
17.992 mm		0.6567"
16.679 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.7600"
19.304 mm		0.6667"
16.933 mm
7/8"6 std0.1667"
4.233 mm		0.8750"
22.225 mm		0.7917"
20.108 mm		0.6883"
17.484 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		0.8950"
22.733 mm		0.7083"
17.992 mm
7/8"5 EST0.2000"
5.080 mm		0.8750"
22.225 mm		0.7750"
19.685 mm		0.6550"
16.637 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		0.8950"
22.733 mm		0.6750"
17.145 mm
7/8"8 EST0.1250"
3.175 mm		0.8750"
22.225 mm		0.8125"
20.637 mm		0.7300"
18.542 mm		0.0725"
1.841 mm		0.0437"
1.111 mm		0.0463"
1.177 mm		0.0437"
1.111 mm		0.8950"
22.733 mm		0.7500"
19.050 mm
7/8"10 EST0.1000"
2.540 mm		0.8750"
22.225 mm		0.8250"
20.955 mm		0.7550"
19.177 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		0.8950"
22.733 mm		0.7750"
19.685 mm
7/8"12 EST0.0833"
2.117 mm		0.8750"
22.225 mm		0.8333"
21.167 mm		0.7817"
19.854 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		0.8850"
22.479 mm		0.7917"
20.108 mm
1"5 std0.2000"
5.080 mm		1.0000"
25.400 mm		0.9000"
22.860 mm		0.7800"
19.812 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		1.0200"
25.908 mm		0.8000"
20.320 mm
1"4 EST0.2500"
6.350 mm		1.0000"
25.400 mm		0.8750"
22.225 mm		0.7300"
18.542 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		1.0200"
25.908 mm		0.7500"
19.050 mm
1"6 EST0.1667"
4.233 mm		1.0000"
25.400 mm		0.9167"
23.283 mm		0.8133"
20.659 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		1.0200"
25.908 mm		0.8333"
21.167 mm
1"8 EST0.1250"
3.175 mm		1.0000"
25.400 mm		0.9375"
23.813 mm		0.8550"
21.717 mm		0.0725"
1.841 mm		0.0437"
1.111 mm		0.0463"
1.177 mm		0.0437"
1.111 mm		1.0200"
25.908 mm		0.8750"
22.225 mm
1"10 EST0.1000"
2.540 mm		1.0000"
25.400 mm		0.9500"
24.130 mm		0.8800"
22.352 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		1.0200"
25.908 mm		0.9000"
22.860 mm
1"12 EST0.0833"
2.117 mm		1.0000"
25.400 mm		0.9583"
24.342 mm		0.9067"
23.029 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		1.0100"
25.654 mm		0.9167"
23.283 mm
1-1/8"5 std0.2000"
5.080 mm		1.1250"
28.575 mm		1.0250"
26.035 mm		0.9050"
22.987 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		1.1450"
29.083 mm		0.9250"
23.495 mm
1-1/8"4 EST0.2500"
6.350 mm		1.1250"
28.575 mm		1.0000"
25.400 mm		0.8550"
21.717 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		1.1450"
29.083 mm		0.8750"
22.225 mm
1-1/8"6 EST0.1667"
4.233 mm		1.1250"
28.575 mm		1.0417"
26.458 mm		0.9383"
23.834 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		1.1450"
29.083 mm		0.9583"
24.342 mm
1-1/8"10 EST0.1000"
2.540 mm		1.1250"
28.575 mm		1.0750"
27.305 mm		1.0050"
25.527 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		1.1450"
29.083 mm		1.0250"
26.035 mm
1-1/8"12 EST0.0833"
2.117 mm		1.1250"
28.575 mm		1.0833"
27.517 mm		1.0317"
26.204 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		1.1350"
28.829 mm		1.0417"
26.458 mm
1-1/4"5 std0.2000"
5.080 mm		1.2500"
31.750 mm		1.1500"
29.210 mm		1.0300"
26.162 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		1.2700"
32.258 mm		1.0500"
26.670 mm
1-1/4"4 EST0.2500"
6.350 mm		1.2500"
31.750 mm		1.1250"
28.575 mm		0.9800"
24.892 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		1.2700"
32.258 mm		1.0000"
25.400 mm
1-1/4"6 EST0.1667"
4.233 mm		1.2500"
31.750 mm		1.1667"
29.633 mm		1.0633"
27.009 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		1.2700"
32.258 mm		1.0833"
27.517 mm
1-1/4"10 EST0.1000"
2.540 mm		1.2500"
31.750 mm		1.2000"
30.480 mm		1.1300"
28.702 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		1.2700"
32.258 mm		1.1500"
29.210 mm
1-1/4"12 EST0.0833"
2.117 mm		1.2500"
31.750 mm		1.2083"
30.692 mm		1.1567"
29.379 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		1.2600"
32.004 mm		1.1667"
29.633 mm
1-3/8"4 std0.2500"
6.350 mm		1.3750"
34.925 mm		1.2500"
31.750 mm		1.1050"
28.067 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		1.3950"
35.433 mm		1.1250"
28.575 mm
1-3/8"5 EST0.2000"
5.080 mm		1.3750"
34.925 mm		1.2750"
32.385 mm		1.1550"
29.337 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		1.3950"
35.433 mm		1.1750"
29.845 mm
1-3/8"6 EST0.1667"
4.233 mm		1.3750"
34.925 mm		1.2917"
32.808 mm		1.1883"
30.184 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		1.3950"
35.433 mm		1.2083"
30.692 mm
1-3/8"10 EST0.1000"
2.540 mm		1.3750"
34.925 mm		1.3250"
33.655 mm		1.2550"
31.877 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		1.3950"
35.433 mm		1.2750"
32.385 mm
1-3/8"12 EST0.0833"
2.117 mm		1.3750"
34.925 mm		1.3333"
33.867 mm		1.2817"
32.554 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		1.3850"
35.179 mm		1.2917"
32.808 mm
1-1/2"4 std0.2500"
6.350 mm		1.5000"
38.100 mm		1.3750"
34.925 mm		1.2300"
31.242 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		1.5200"
38.608 mm		1.2500"
31.750 mm
1-1/2"3 EST0.3333"
8.467 mm		1.5000"
38.100 mm		1.3333"
33.867 mm		1.1467"
29.125 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		1.5200"
38.608 mm		1.1667"
29.633 mm
1-1/2"5 EST0.2000"
5.080 mm		1.5000"
38.100 mm		1.4000"
35.560 mm		1.2800"
32.512 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		1.5200"
38.608 mm		1.3000"
33.020 mm
1-1/2"6 EST0.1667"
4.233 mm		1.5000"
38.100 mm		1.4167"
35.983 mm		1.3133"
33.359 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		1.5200"
38.608 mm		1.3333"
33.867 mm
1-1/2"10 EST0.1000"
2.540 mm		1.5000"
38.100 mm		1.4500"
36.830 mm		1.3800"
35.052 mm		0.0600"
1.524 mm		0.0345"
0.876 mm		0.0371"
0.942 mm		0.0345"
0.876 mm		1.5200"
38.608 mm		1.4000"
35.560 mm
1-1/2"12 EST0.0833"
2.117 mm		1.5000"
38.100 mm		1.4583"
37.042 mm		1.4067"
35.729 mm		0.0467"
1.185 mm		0.0296"
0.752 mm		0.0309"
0.785 mm		0.0296"
0.752 mm		1.5100"
38.354 mm		1.4167"
35.983 mm
1-3/4"4 std0.2500"
6.350 mm		1.7500"
44.450 mm		1.6250"
41.275 mm		1.4800"
37.592 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		1.7700"
44.958 mm		1.5000"
38.100 mm
1-3/4"3 EST0.3333"
8.467 mm		1.7500"
44.450 mm		1.5833"
40.217 mm		1.3967"
35.475 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		1.7700"
44.958 mm		1.4167"
35.983 mm
1-3/4"5 EST0.2000"
5.080 mm		1.7500"
44.450 mm		1.6500"
41.910 mm		1.5300"
38.862 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		1.7700"
44.958 mm		1.5500"
39.370 mm
1-3/4"6 EST0.1667"
4.233 mm		1.7500"
44.450 mm		1.6667"
42.333 mm		1.5633"
39.709 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		1.7700"
44.958 mm		1.5833"
40.217 mm
2"4 std0.2500"
6.350 mm		2.0000"
50.800 mm		1.8750"
47.625 mm		1.7300"
43.942 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		2.0200"
51.308 mm		1.7500"
44.450 mm
2"3 EST0.3333"
8.467 mm		2.0000"
50.800 mm		1.8333"
46.567 mm		1.6467"
41.825 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		2.0200"
51.308 mm		1.6667"
42.333 mm
2"5 EST0.2000"
5.080 mm		2.0000"
50.800 mm		1.9000"
48.260 mm		1.7800"
45.212 mm		0.1100"
2.794 mm		0.0716"
1.817 mm		0.0741"
1.883 mm		0.0716"
1.817 mm		2.0200"
51.308 mm		1.8000"
45.720 mm
2"6 EST0.1667"
4.233 mm		2.0000"
50.800 mm		1.9167"
48.683 mm		1.8133"
46.059 mm		0.0933"
2.371 mm		0.0592"
1.504 mm		0.0618"
1.569 mm		0.0592"
1.504 mm		2.0200"
51.308 mm		1.8333"
46.567 mm
2-1/4"3 std0.3333"
8.467 mm		2.2500"
57.150 mm		2.0833"
52.917 mm		1.8967"
48.175 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		2.2700"
57.658 mm		1.9167"
48.683 mm
2-1/4"4 EST0.2500"
6.350 mm		2.2500"
57.150 mm		2.1250"
53.975 mm		1.9800"
50.292 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		2.2700"
57.658 mm		2.0000"
50.800 mm
2-1/2"3 std0.3333"
8.467 mm		2.5000"
63.500 mm		2.3333"
59.267 mm		2.1467"
54.525 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		2.5200"
64.008 mm		2.1667"
55.033 mm
2-1/2"2 EST0.5000"
12.700 mm		2.5000"
63.500 mm		2.2500"
57.150 mm		1.9800"
50.292 mm		0.2600"
6.604 mm		0.1828"
4.642 mm		0.1853"
4.708 mm		0.1828"
4.642 mm		2.5200"
64.008 mm		2.0000"
50.800 mm
2-1/2"4 EST0.2500"
6.350 mm		2.5000"
63.500 mm		2.3750"
60.325 mm		2.2300"
56.642 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		2.5200"
64.008 mm		2.2500"
57.150 mm
2-3/4"3 std0.3333"
8.467 mm		2.7500"
69.850 mm		2.5833"
65.617 mm		2.3967"
60.875 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		2.7700"
70.358 mm		2.4167"
61.383 mm
2-3/4"2 EST0.5000"
12.700 mm		2.7500"
69.850 mm		2.5000"
63.500 mm		2.2300"
56.642 mm		0.2600"
6.604 mm		0.1828"
4.642 mm		0.1853"
4.708 mm		0.1828"
4.642 mm		2.7700"
70.358 mm		2.2500"
57.150 mm
2-3/4"4 EST0.2500"
6.350 mm		2.7500"
69.850 mm		2.6250"
66.675 mm		2.4800"
62.992 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		2.7700"
70.358 mm		2.5000"
63.500 mm
3"2 std0.5000"
12.700 mm		3.0000"
76.200 mm		2.7500"
69.850 mm		2.4800"
62.992 mm		0.2600"
6.604 mm		0.1828"
4.642 mm		0.1853"
4.708 mm		0.1828"
4.642 mm		3.0200"
76.708 mm		2.5000"
63.500 mm
3"3 EST0.3333"
8.467 mm		3.0000"
76.200 mm		2.8333"
71.967 mm		2.6467"
67.225 mm		0.1767"
4.487 mm		0.1210"
3.073 mm		0.1236"
3.139 mm		0.1210"
3.073 mm		3.0200"
76.708 mm		2.6667"
67.733 mm
3"4 EST0.2500"
6.350 mm		3.0000"
76.200 mm		2.8750"
73.025 mm		2.7300"
69.342 mm		0.1350"
3.429 mm		0.0901"
2.288 mm		0.0927"
2.354 mm		0.0901"
2.288 mm		3.0200"
76.708 mm		2.7500"
69.850 mm

Twin-start and other multi-start threads: the dimensions above stay the same, because depth and diameters depend on the pitch. The lead is starts × pitch (a 1"-5 twin start has a 0.400" lead). Choose the starts in the calculator above for the lead, helix angle, gear setting and indexing.

Worked out from the ASME B1.5 general-purpose formulas, not copied from the standard’s tables. P = 1/TPI, basic depth = 0.5P, basic pitch dia = D − 0.5P, basic crest and root flat = 0.3707P. The major and minor clearance c is 0.010" for 10 TPI and coarser and 0.005" for finer pitches. Screw minor = D − P − 2c, thread depth = 0.5P + c, tool tip width = 0.3707P − 0.259c, nut major = D + 2c, and the nut is bored to the basic minor, D − P. These are basic/nominal values. Class 2G (or 3G/4G) tolerances and allowances, which make the real screw slightly smaller and the nut slightly larger, must come from ASME B1.5 or your nut maker. Grind the tool tip to the width shown, or very slightly narrower. Check the fit with the mating nut.

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