Reference
ISO metric coarse thread chart
ISO metric coarse thread dimensions from M6 to M52: pitch, pitch diameter, minor diameter and stress area, with the formulas each value comes from.
Pitch, pitch diameter, minor diameter and tensile stress area for the ISO metric coarse series from M6 to M52. Every figure is computed from the published profile relationships rather than copied from a table, so the formulas are shown and any row can be recalculated.
Where each column comes from
The pitch is a selected value from the coarse column of ISO 261. Everything else follows from the 60-degree basic profile of ISO 68-1 and is the same arithmetic ISO 724 tabulates.
d2 = d − 0,6495 × PD1 = d − 1,0825 × Pd3 = d − 1,2269 × PAs = π/4 × ((d2 + d3) / 2)²
| Size | Pitch P | Pitch diameter d2 | Minor diameter D1 | Stress area As | Source check |
|---|---|---|---|---|---|
| M6 | 1.00 | 5.350 | 4.917 | 20.1 | pitch diameter only |
| M8 | 1.25 | 7.188 | 6.647 | 36.6 | matched in ISO 724 |
| M10 | 1.50 | 9.026 | 8.376 | 58.0 | pitch diameter only |
| M12 | 1.75 | 10.863 | 10.106 | 84.3 | matched in ISO 724 |
| M14 | 2.00 | 12.701 | 11.835 | 115.4 | matched in ISO 724 |
| M16 | 2.00 | 14.701 | 13.835 | 156.7 | matched in ISO 724 |
| M18 | 2.50 | 16.376 | 15.294 | 192.5 | matched in ISO 724 |
| M20 | 2.50 | 18.376 | 17.294 | 244.8 | matched in ISO 724 |
| M22 | 2.50 | 20.376 | 19.294 | 303.4 | matched in ISO 724 |
| M24 | 3.00 | 22.051 | 20.752 | 352.5 | matched in ISO 724 |
| M27 | 3.00 | 25.051 | 23.752 | 459.4 | matched in ISO 724 |
| M30 | 3.50 | 27.727 | 26.211 | 560.6 | matched in ISO 724 |
| M33 | 3.50 | 30.727 | 29.211 | 693.6 | matched in ISO 724 |
| M36 | 4.00 | 33.402 | 31.670 | 816.7 | matched in ISO 724 |
| M39 | 4.00 | 36.402 | 34.670 | 975.8 | matched in ISO 724 |
| M42 | 4.50 | 39.077 | 37.129 | 1,120.9 | matched in ISO 724 |
| M45 | 4.50 | 42.077 | 40.129 | 1,306.0 | matched in ISO 724 |
| M48 | 5.00 | 44.752 | 42.587 | 1,473.1 | matched in ISO 724 |
| M52 | 5.00 | 48.752 | 46.587 | 1,757.8 | matched in ISO 724 |
How these numbers were checked
Seventeen of the nineteen rows have both their pitch diameter and their minor diameter matched, digit for digit, against the ISO 724 table itself. For M6 and M10 only the pitch diameter matched, because the scan of the source is illegible at those two cells. Separately, all six sizes for which ISO 898-1 Table 7 gives a tensile stress area agree with it: 84.3, 157, 245, 353, 561 and 817 mm2. Two independent checks, not a transcription.
What this chart is not
These are basic dimensions. They are not limits of size: a thread callout also needs a tolerance class from ISO 965, and the applicable standard is the one named on the drawing. Fine pitches are excluded, and so are sizes below M6 and above M52, because the source scan could not be read reliably at those rows.
Sources
- ISO 261:1998 — ISO general purpose metric screw threads, general plan; the coarse pitch column.
- ISO 724:1993 — basic dimensions for the same series.
- IS 4218-2:2001 and IS 4218-3:1999 — the Bureau of Indian Standards adoptions of ISO 261 and ISO 724, published in full under India’s right-to-information disclosure. These are the copies the values above were checked against.
- ISO 898-1:2013 — Table 7 stress areas, used as the independent second check.
- ISO 965-1 — the tolerance system a thread callout needs beyond these basic dimensions.
Threads are only half of a thread callout.
Send the drawing with the tolerance class, the gauging method and whether thread depth is functional. A dimension without an acceptance rule is still open when the part arrives.
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