Metric thread chart: tap drills, clearance holes and counterbores
Coarse-pitch ISO metric threads with the hole sizes you need to model and draw them.
| Thread | Pitch | Tap drill | Clearance fine | Clearance medium | Clearance coarse | Counterbore Ø |
|---|---|---|---|---|---|---|
| M2 | 0.4 | 1.6 | 2.2 | 2.4 | 2.6 | 4.4 |
| M2.5 | 0.45 | 2.05 | 2.7 | 2.9 | 3.1 | 5.5 |
| M3 | 0.5 | 2.5 | 3.2 | 3.4 | 3.6 | 6.5 |
| M4 | 0.7 | 3.3 | 4.3 | 4.5 | 4.8 | 8 |
| M5 | 0.8 | 4.2 | 5.3 | 5.5 | 5.8 | 10 |
| M6 | 1 | 5 | 6.4 | 6.6 | 7 | 11 |
| M8 | 1.25 | 6.8 | 8.4 | 9 | 10 | 15 |
| M10 | 1.5 | 8.5 | 10.5 | 11 | 12 | 18 |
| M12 | 1.75 | 10.2 | 13 | 13.5 | 14.5 | 20 |
| M14 | 2 | 12 | 15 | 15.5 | 16.5 | 24 |
| M16 | 2 | 14 | 17 | 17.5 | 18.5 | 26 |
| M20 | 2.5 | 17.5 | 21 | 22 | 24 | 33 |
| M24 | 3 | 21 | 25 | 26 | 28 | 40 |
| M30 | 3.5 | 26.5 | 31 | 33 | 35 | 48 |
Sizes in mm. Clearance holes per ISO 273, counterbore diameters for ISO 4762 socket head cap screws per DIN 974-1 (row 1). Tap drill sizes are for cutting taps; forming taps need larger holes.
How to use this table
Model a threaded hole at the tap drill diameter and add a cosmetic thread in CAD. STEP files do not carry thread information, so the drawing must state the thread: for example M6x1-6H, 12 deep. For bolt holes, medium clearance suits most parts; fine clearance gives better location, coarse helps when hole positions vary.
Draw your own part
Drop a STEP file into DrawMyPart. It finds every body, asks you to confirm threads, fits and tolerances, and draws a sheet your manufacturer can build from.
Open the tool