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1-inch bolt size
1-1/2 in wrench
across-flats spanner / socket size for 1 in
1-inch bolt — very heavy structural anchoring.
Full specification
| System | Imperial UNC |
| Nominal diameter | 1 in (25.4 mm) |
| Thread pitch | 8 TPI |
| Wrench / spanner (across flats) | 1-1/2 in |
| Tap drill | 7/8 in (22.2 mm) |
| Clearance hole | 1-1/32 in |
| Common grade / class | Grade 5 |
| Typical torque | 868 Nm (640 ft·lb) |
| Closest other-system size | ~M24 |
🔧 Torque unit converter
Pre-filled with the typical torque for 1 in (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 1 in
The 1 inch-8 bolt is a very heavy anchor and structural fastener.
Joints this large are normally torqued with calibrated hydraulic equipment.
Frequently asked questions
- What size wrench or spanner fits 1 in?
- 1-inch bolt uses a 1-1/2 in wrench or spanner, measured across the flats of the hex head.
- What is the torque for 1 in?
- A typical tightening torque for 1-inch bolt in Grade 5 on dry threads is about 868 Nm (640 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does 1 in use?
- 1-inch bolt has a thread pitch of 8 TPI and uses a 7/8 in (22.2 mm) tap drill, with a 1-1/32 in clearance hole.