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M8 flange bolt size
12 mm wrench
across-flats spanner / socket size for M8 flange
M8 flange bolt — automotive exhausts and brackets.
Full specification
| System | Metric flange |
| Nominal diameter | 8 mm |
| Thread pitch | 1.25 mm |
| Wrench / spanner (across flats) | 12 mm |
| Tap drill | 6.8 mm |
| Clearance hole | 9 mm |
| Common grade / class | 10.9 |
| Typical torque | 28 Nm (21 ft·lb) |
| Closest other-system size | ~5/16 inch flange |
🔧 Torque unit converter
Pre-filled with the typical torque for M8 flange (10.9, dry). Edit any field to convert.
⚠️ Torque values here are general references for 10.9 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 M8 flange
M8 flange bolts are common on exhaust clamps, brackets and suspension.
Many M8 flange bolts use a 12 mm head, not 13 mm — check before grabbing a socket.
Frequently asked questions
- What size wrench or spanner fits M8 flange?
- M8 flange bolt uses a 12 mm wrench or spanner, measured across the flats of the hex head.
- What is the torque for M8 flange?
- A typical tightening torque for M8 flange bolt in 10.9 on dry threads is about 28 Nm (21 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does M8 flange use?
- M8 flange bolt has a thread pitch of 1.25 mm and uses a 6.8 mm tap drill, with a 9 mm clearance hole.