Shoulder Bolt vs. Hex Bolt
A shoulder bolt is a precision pivot pin that also threads in — a hex bolt just clamps.
| Feature | Shoulder Bolt | Hex Bolt |
|---|---|---|
| Shank | Precision-ground bearing surface | Rolled, for clamping |
| Purpose | Pivot, axle, locating pin | Clamping force |
| Tolerance | Close — machined | Loose |
| Thread | Smaller than the shoulder | Full size |
| Best for | Pulleys, cams, linkages | Structural and general bolting |
Verdict
Use a shoulder bolt when a part must rotate or slide on the bolt. Use a hex bolt for clamping two parts together.