Socket Head Cap Screw Spec Table
Also called Allen bolt or cap screw, it has a hexagonal socket in the head driven by an Allen key. Its low-profile head suits tight spaces and flush surface requirements.
Practical Notes
- Allen key size differs per bolt (M5→4mm, M6→5mm, M8→6mm, M10→8mm). Wrong size strips the socket permanently.
- When recessing bolts in counterbores, verify tool clearance (socket wrench OD + finger room). It fits in CAD but often not on the shop floor.
Selection Guide
Use where bolt heads must not protrude or wrench space is limited. Allen keys need only socket-diameter clearance. Standard for precision assemblies like molds, jigs, and robot joints. Default grades 10.9/12.9 provide higher clamping force than equivalent hex bolts. However, hex sockets can clog with debris, so hex bolts may be preferable in dusty or outdoor environments.
Socket Head Cap Screw
ISOJISDINANSISocket Head Cap Screw
11 sizesThe dimensions below are identical across ISO 4762 · JIS B 1176 · DIN 912 · ASME B18.3.1M.
| Nominal | d | P | dk (Head Dia) | k (Head H.) | s (Wrench) |
|---|---|---|---|---|---|
| M3 | 3 | 0.5 | 5.5 | 3 | 2.5 |
| M4 | 4 | 0.7 | 7 | 4 | 3 |
| M5 | 5 | 0.8 | 8.5 | 5 | 4 |
| M6 | 6 | 1 | 10 | 6 | 5 |
| M8 | 8 | 1.25 | 13 | 8 | 6 |
| M10 | 10 | 1.5 | 16 | 10 | 8 |
| M12 | 12 | 1.75 | 18 | 12 | 10 |
| M14 | 14 | 2 | 21 | 14 | 12 |
| M16 | 16 | 2 | 24 | 16 | 14 |
| M20 | 20 | 2.5 | 30 | 20 | 17 |
| M24 | 24 | 3 | 36 | 24 | 19 |
Key Features
- Hex socket (Allen) head allows flush or recessed mounting below surface
- Default grades 10.9/12.9; SCM435 heat-treated for high tensile strength
- KS B 1003 / ISO 4762 / DIN 912 compliant; M2–M36 range supported
Key Applications
Mold assembly, CNC jigs/fixtures, robot joints, precision machine covers, semiconductor equipment
STEP File Downloads
Free 3D CAD models (STEP AP214). Built to real standard dimensions; threads are simplified (plain shank) per free-library convention.
FAQ
What are the counterbore dimensions for socket head cap screws?
For M8: counterbore diameter ø14mm, depth 8.5mm (head height 8mm + 0.5mm clearance). Refer to counterbore spec tables for each size.
Difference between grade 10.9 and 12.9?
10.9: tensile 1040MPa, yield 940MPa. 12.9: tensile 1220MPa, yield 1100MPa. Grade 12.9 is strongest but more susceptible to hydrogen embrittlement.