Metric coarse threads: dimensions and tap drill
Full chart with the tap drill for every size. Press “Calculate” on any row to open the calculator with that thread.
The coarse series is the default metric thread: if the drawing just says “M12”, it means M12 x 1.75. It is the most forgiving with assembly and dirt, and the one you will find in any tap and fastener catalogue.
Common metric threads: M6, M8, M10 and M12
In M8 × 1.25, M denotes a metric thread, 8 is the nominal diameter in mm, and 1.25 is the pitch in mm. This table covers coarse pitches; use the fine-pitch table when the drawing specifies a different pitch.
Choose the diameter and pitch from the table, then calculate the tap drill or prepare the threading cycle.
| Thread | Pitch (mm) | Major Ø (mm) | Drill for cutting tap | Drill for forming tap | Nut minor Ø (mm) | Calculate |
|---|---|---|---|---|---|---|
| M1 x 0.25 | 0.25 | 1 | ⌀ 0.75 | ⌀ 0.9 | 0.729 | |
| M1.2 x 0.25 | 0.25 | 1.2 | ⌀ 0.95 | ⌀ 1.05 | 0.929 | |
| M1.4 x 0.3 | 0.3 | 1.4 | ⌀ 1.1 | ⌀ 1.25 | 1.075 | |
| M1.6 x 0.35 | 0.35 | 1.6 | ⌀ 1.25 | ⌀ 1.45 | 1.221 | |
| M1.8 x 0.35 | 0.35 | 1.8 | ⌀ 1.45 | ⌀ 1.65 | 1.421 | |
| M2 x 0.4 | 0.4 | 2 | ⌀ 1.6 | ⌀ 1.8 | 1.567 | |
| M2.5 x 0.45 | 0.45 | 2.5 | ⌀ 2.05 | ⌀ 2.3 | 2.013 | |
| M3 x 0.5 | 0.5 | 3 | ⌀ 2.5 | ⌀ 2.75 | 2.459 | |
| M3.5 x 0.6 | 0.6 | 3.5 | ⌀ 2.9 | ⌀ 3.2 | 2.85 | |
| M4 x 0.7 | 0.7 | 4 | ⌀ 3.3 | ⌀ 3.6 | 3.242 | |
| M5 x 0.8 | 0.8 | 5 | ⌀ 4.2 | ⌀ 4.6 | 4.134 | |
| M6 x 1 | 1 | 6 | ⌀ 5 | ⌀ 5.5 | 4.917 | |
| M7 x 1 | 1 | 7 | ⌀ 6 | ⌀ 6.5 | 5.917 | |
| M8 x 1.25 | 1.25 | 8 | ⌀ 6.8 | ⌀ 7.4 | 6.647 | |
| M10 x 1.5 | 1.5 | 10 | ⌀ 8.5 | ⌀ 9.3 | 8.376 | |
| M12 x 1.75 | 1.75 | 12 | ⌀ 10.2 | ⌀ 11.1 | 10.106 | |
| M14 x 2 | 2 | 14 | ⌀ 12 | ⌀ 13 | 11.835 | |
| M16 x 2 | 2 | 16 | ⌀ 14 | ⌀ 15 | 13.835 | |
| M18 x 2.5 | 2.5 | 18 | ⌀ 15.5 | ⌀ 17 | 15.294 | |
| M20 x 2.5 | 2.5 | 20 | ⌀ 17.5 | ⌀ 19 | 17.294 | |
| M22 x 2.5 | 2.5 | 22 | ⌀ 19.5 | ⌀ 21 | 19.294 | |
| M24 x 3 | 3 | 24 | ⌀ 21 | ⌀ 22.5 | 20.752 | |
| M27 x 3 | 3 | 27 | ⌀ 24 | ⌀ 25.5 | 23.752 | |
| M30 x 3.5 | 3.5 | 30 | ⌀ 26.5 | ⌀ 28.5 | 26.211 | |
| M33 x 3.5 | 3.5 | 33 | ⌀ 29.5 | ⌀ 31.5 | 29.211 | |
| M36 x 4 | 4 | 36 | ⌀ 32 | ⌀ 34 | 31.67 | |
| M39 x 4 | 4 | 39 | ⌀ 35 | ⌀ 37 | 34.67 | |
| M42 x 4.5 | 4.5 | 42 | ⌀ 37.5 | ⌀ 40 | 37.129 | |
| M45 x 4.5 | 4.5 | 45 | ⌀ 40.5 | ⌀ 43 | 40.129 | |
| M48 x 5 | 5 | 48 | ⌀ 43 | ⌀ 45.5 | 42.587 | |
| M52 x 5 | 5 | 52 | ⌀ 47 | ⌀ 49.5 | 46.587 | |
| M56 x 5.5 | 5.5 | 56 | ⌀ 50.5 | ⌀ 53.5 | 50.046 | |
| M60 x 5.5 | 5.5 | 60 | ⌀ 54.5 | ⌀ 57.5 | 54.046 | |
| M64 x 6 | 6 | 64 | ⌀ 58 | ⌀ 61 | 57.505 | |
| M68 x 6 | 6 | 68 | ⌀ 62 | ⌀ 65 | 61.505 | |
| M72 x 6 | 6 | 72 | ⌀ 66 | ⌀ 69 | 65.505 | |
| M76 x 6 | 6 | 76 | ⌀ 70 | ⌀ 73 | 69.505 | |
| M80 x 6 | 6 | 80 | ⌀ 74 | ⌀ 77 | 73.505 | |
| M85 x 6 | 6 | 85 | ⌀ 79 | ⌀ 82 | 78.505 | |
| M90 x 6 | 6 | 90 | ⌀ 84 | ⌀ 87 | 83.505 | |
| M95 x 6 | 6 | 95 | ⌀ 89 | ⌀ 92 | 88.505 | |
| M100 x 6 | 6 | 100 | ⌀ 94 | ⌀ 97 | 93.505 |
How to read the chart
Drill for a cutting tap: nominal diameter minus pitch (D − P), rounded to the nearest standard drill, for 75 % thread engagement.
Drill for a forming tap: the tap does not cut, it displaces material, so the hole is larger (approx. D − 0.5·P). Drilling for a cutting tap and then using a forming tap breaks it.
Nut minor Ø: theoretical internal diameter of the ISO profile. Use it to check the hole with a gauge or as the reference for thread milling.
“Calculate” opens the calculator with that size: G84 cycle, feed, blind hole depth and recommended method for the material. Indicative values for 6H/6g threads; for critical parts, check the tap maker's chart.
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