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M12 bolt size
19 mm wrench
across-flats spanner / socket size for M12
M12 bolt — structural, automotive and machinery.
Full specification
| System | Metric coarse |
| Nominal diameter | 12 mm |
| Thread pitch | 1.75 mm |
| Wrench / spanner (across flats) | 19 mm |
| Tap drill | 10.2 mm |
| Clearance hole | 13.5 mm |
| Common grade / class | 8.8 |
| Typical torque | 85 Nm (63 ft·lb) |
| Closest other-system size | ~1/2 inch |
🔧 Torque unit converter
Pre-filled with the typical torque for M12 (8.8, dry). Edit any field to convert.
⚠️ Torque values here are general references for 8.8 on clean, dry threads. Lubrication, coatings, and the joint material change the figure significantly. For structural, automotive, or safety-critical work, always use the torque specified by the manufacturer or engineer.
About M12
M12 is a structural size used in machinery frames, towbars and heavy mounts.
M12 commonly uses an 18 mm or 19 mm head depending on standard — verify the flats.
Frequently asked questions
- What size wrench or spanner fits M12?
- M12 bolt uses a 19 mm wrench or spanner, measured across the flats of the hex head.
- What is the torque for M12?
- A typical tightening torque for M12 bolt in 8.8 on dry threads is about 85 Nm (63 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does M12 use?
- M12 bolt has a thread pitch of 1.75 mm and uses a 10.2 mm tap drill, with a 13.5 mm clearance hole.