M10 thread sizes
8.5 mm tapping drill · 11 mm clearance
1.5 mm coarse pitch · 1.25 mm fine · 8 mm hex key · 17/16 mm spanner
What M10 is used for
Structural brackets, suspension components, heavy furniture.
Every number for M10
| Major diameter | 10 mm |
| Coarse pitch | 1.5 mm |
| Fine pitch | 1.25 mm (M10×1.25) |
| Tapping drill, coarse | 8.5 mm (10 − 1.5 = 8.5) |
| Tapping drill, fine | 8.75 mm |
| Clearance hole, normal | 11 mm |
| Hex key (socket head) | 8 mm |
| Spanner (hex head) | 17 mm — or 16 mm under ISO 4017 |
| Tapped depth, steel | 15.0 mm (1.5 × diameter) |
| Tapped depth, aluminium | 20.0 mm (2 × diameter) |
Where the drill size comes from
A tapping drill leaves enough material for the tap to cut a thread, and the amount it has to leave is one pitch: drill = major diameter − pitch. For M10 coarse that is 10 − 1.5 = 8.5 mm. The rule holds for the fine series too — M10×1.25 is drilled 8.75 mm.
Going slightly larger gives a shallower thread that is easier to tap and weaker; going smaller risks breaking the tap. The standard drill aims at about 75% thread engagement, which is where the strength stops improving enough to be worth the extra effort.
Nearby sizes
| Thread | Pitch | Tapping drill | Clearance | Hex key |
|---|---|---|---|---|
| M2 | 0.4 mm | 1.6 mm | 2.4 mm | 1.5 mm |
| M2.5 | 0.45 mm | 2.05 mm | 2.9 mm | 2 mm |
| M3 | 0.5 mm | 2.5 mm | 3.4 mm | 2.5 mm |
| M4 | 0.7 mm | 3.3 mm | 4.5 mm | 3 mm |
| M5 | 0.8 mm | 4.2 mm | 5.5 mm | 4 mm |
| M6 | 1 mm | 5 mm | 6.6 mm | 5 mm |
Frequently asked questions
What drill size for M10?
8.5 mm for a coarse thread. The rule is major diameter minus pitch: 10 − 1.5 = 8.5.
What is the clearance hole for M10?
11 mm for a normal fit under ISO 273. A close fit is about 10.6 mm and a loose fit around 12.0 mm — the clearance hole is the one in the part the bolt passes through, not the one being tapped.
What size spanner for an M10 bolt?
17 mm or 16 mm — the standards disagree at this size. DIN 933 specifies 17 mm across the flats and ISO 4017 specifies 16. Both bolts are M10; only the head differs, which is why a socket set can seem to be missing a size.
What is the pitch of M10?
1.5 mm coarse, or 1.25 mm in the fine series (M10×1.25). Pitch is the distance between adjacent thread crests, so one full turn advances the bolt 1.5 mm.