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5/16-24 UNF bolt size
1/2 in wrench
across-flats spanner / socket size for 5/16-24
5/16-24 UNF bolt — automotive fittings.
Full specification
| System | Imperial UNF |
| Nominal diameter | 5/16 in (7.94 mm) |
| Thread pitch | 24 TPI (fine) |
| Wrench / spanner (across flats) | 1/2 in |
| Tap drill | I (6.9 mm) |
| Clearance hole | 21/64 in |
| Common grade / class | Grade 5 |
| Typical torque | 34 Nm (25 ft·lb) |
| Closest other-system size | ~5/16-18 coarse |
🔧 Torque unit converter
Pre-filled with the typical torque for 5/16-24 (Grade 5, dry). Edit any field to convert.
⚠️ Torque values here are general references for Grade 5 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 5/16-24
5/16-24 fine thread appears on automotive fittings and adjusters.
Fine threads hold better in thin material but cross-thread more easily.
Frequently asked questions
- What size wrench or spanner fits 5/16-24?
- 5/16-24 UNF bolt uses a 1/2 in wrench or spanner, measured across the flats of the hex head.
- What is the torque for 5/16-24?
- A typical tightening torque for 5/16-24 UNF bolt in Grade 5 on dry threads is about 34 Nm (25 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does 5/16-24 use?
- 5/16-24 UNF bolt has a thread pitch of 24 TPI (fine) and uses a I (6.9 mm) tap drill, with a 21/64 in clearance hole.