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1/4-inch lag screw size
7/16 in wrench
across-flats spanner / socket size for 1/4 in lag
1/4-inch lag screw — light timber fixings.
Full specification
| System | Imperial lag |
| Nominal diameter | 1/4 in (6.35 mm) |
| Thread pitch | coarse wood thread |
| Wrench / spanner (across flats) | 7/16 in |
| Tap drill | 5/32 in pilot |
| Clearance hole | 1/4 in |
| Common grade / class | Low-carbon steel |
| Typical torque | 13 Nm (9.6 ft·lb) |
| Closest other-system size | ~M6 coach |
🔧 Torque unit converter
Pre-filled with the typical torque for 1/4 in lag (Low-carbon steel, dry). Edit any field to convert.
⚠️ Torque values here are general references for Low-carbon steel 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 1/4 in lag
1/4 inch lag screws fix light timber framing and brackets to wood.
Always drill a pilot hole — lag screws split timber without one.
Frequently asked questions
- What size wrench or spanner fits 1/4 in lag?
- 1/4-inch lag screw uses a 7/16 in wrench or spanner, measured across the flats of the hex head.
- What is the torque for 1/4 in lag?
- A typical tightening torque for 1/4-inch lag screw in Low-carbon steel on dry threads is about 13 Nm (9.6 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does 1/4 in lag use?
- 1/4-inch lag screw has a thread pitch of coarse wood thread and uses a 5/32 in pilot tap drill, with a 1/4 in clearance hole.