M14 thread sizes
12 mm tapping drill · 15.5 mm clearance
2 mm coarse pitch · 1.5 mm fine · 12 mm hex key · 22/21 mm spanner
What M14 is used for
Uncommon in general work; found in vehicle and machine assemblies.
Every number for M14
| Major diameter | 14 mm |
| Coarse pitch | 2 mm |
| Fine pitch | 1.5 mm (M14×1.5) |
| Tapping drill, coarse | 12 mm (14 − 2 = 12) |
| Tapping drill, fine | 12.5 mm |
| Clearance hole, normal | 15.5 mm |
| Hex key (socket head) | 12 mm |
| Spanner (hex head) | 22 mm — or 21 mm under ISO 4017 |
| Tapped depth, steel | 21.0 mm (1.5 × diameter) |
| Tapped depth, aluminium | 28.0 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 M14 coarse that is 14 − 2 = 12 mm. The rule holds for the fine series too — M14×1.5 is drilled 12.5 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 |
|---|---|---|---|---|
| M6 | 1 mm | 5 mm | 6.6 mm | 5 mm |
| M8 | 1.25 mm | 6.8 mm | 9 mm | 6 mm |
| M10 | 1.5 mm | 8.5 mm | 11 mm | 8 mm |
| M12 | 1.75 mm | 10.2 mm | 13.5 mm | 10 mm |
| M16 | 2 mm | 14 mm | 17.5 mm | 14 mm |
| M20 | 2.5 mm | 17.5 mm | 22 mm | 17 mm |
Frequently asked questions
What drill size for M14?
12 mm for a coarse thread. The rule is major diameter minus pitch: 14 − 2 = 12.
What is the clearance hole for M14?
15.5 mm for a normal fit under ISO 273. A close fit is about 15.1 mm and a loose fit around 16.5 mm — the clearance hole is the one in the part the bolt passes through, not the one being tapped.
What size spanner for an M14 bolt?
22 mm or 21 mm — the standards disagree at this size. DIN 933 specifies 22 mm across the flats and ISO 4017 specifies 21. Both bolts are M14; only the head differs, which is why a socket set can seem to be missing a size.
What is the pitch of M14?
2 mm coarse, or 1.5 mm in the fine series (M14×1.5). Pitch is the distance between adjacent thread crests, so one full turn advances the bolt 2 mm.