Home › Socket Cap Screws › 1/4 socket cap
1/4 inch socket cap screw size
3/16 in hex key
Allen / internal hex key size for 1/4 socket cap
1/4 inch socket cap screw — machine tooling and fixtures.
Full specification
| System | Imperial (Alloy) |
| Nominal diameter | 1/4 in (6.35 mm) |
| Thread pitch | 20 TPI |
| Hex key (Allen) | 3/16 in |
| Tap drill | #7 (5.1 mm) |
| Clearance hole | 17/64 in |
| Common grade / class | Alloy (180 ksi) |
| Typical torque | 17 Nm (12.5 ft·lb) |
| Closest other-system size | ~M6 |
🔧 Torque unit converter
Pre-filled with the typical torque for 1/4 socket cap (Alloy (180 ksi), dry). Edit any field to convert.
⚠️ Torque values here are general references for Alloy (180 ksi) 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 socket cap
The 1/4-20 socket cap screw is a common imperial tooling fastener.
A 3/16 in hex key drives 1/4-20 socket caps.
Frequently asked questions
- What size Allen / hex key fits 1/4 socket cap?
- 1/4 inch socket cap screw uses a 3/16 in hex (Allen) key with an internal hex drive.
- What is the torque for 1/4 socket cap?
- A typical tightening torque for 1/4 inch socket cap screw in Alloy (180 ksi) on dry threads is about 17 Nm (12.5 ft·lb). Always confirm against the manufacturer spec for important joints.
- What thread pitch and tap drill does 1/4 socket cap use?
- 1/4 inch socket cap screw has a thread pitch of 20 TPI and uses a #7 (5.1 mm) tap drill, with a 17/64 in clearance hole.