Hex Head vs. Socket Head Cap
Comparing 2 standards across 12 specifications. 12 key differences identified.
Hex Head Bolts (standardized under ISO 4014 / DIN 931 for partially threaded bolts and ISO 4017 / DIN 933 for fully threaded tap bolts) feature a 6-sided external polygon head driven by open-end wrenches, box wrenches, or ratcheting sockets. It is the global benchmark for high-torque heavy structural and automotive clamping.
Socket Head Cap Screws (SHCS, standardized under DIN 912 and ISO 4762) feature a compact cylindrical head whose height is approximately equal to the screw shank diameter, housing a deep internal hexagonal (Allen) or Torx socket. Engineered for high-tensile alloy steel applications, it allows high-torque fastening inside tight, counterbored machine recesses.
Specification Comparison Table
12 Parameters| Parameter / Spec | ||
|---|---|---|
|
Standard Specifications
|
ISO 4014 (Partial thread) / ISO 4017 (Full thread) / DIN 931 / ASME B18.2.1 | ISO 4762 / DIN 912 / ASME B18.3 |
|
Head Geometry
|
6-sided external hexagon with flat top face and circular washer face underside | Tall cylindrical head with knurled or smooth outer diameter |
|
Common Metric Wrench Sizes
|
M6 (10mm), M8 (13mm), M10 (16/17mm), M12 (18/19mm), M16 (24mm) | — |
|
Common Imperial Wrench Sizes
|
1/4" (7/16"), 3/8" (9/16"), 1/2" (3/4"), 3/4" (1-1/8") | — |
|
Strength Markings (Metric)
|
Class 8.8, 10.9, 12.9 stamped directly on head top | — |
|
Strength Markings (Imperial)
|
Grade 2 (plain), Grade 5 (3 radial lines), Grade 8 (6 radial lines) | — |
|
Flanged Variant
|
DIN 6921 (Hex head with integrated wide washer flange) | — |
|
Head Height Ratio
|
— | Head Height ≈ Screw Major Diameter (H ≈ D) |
|
Head Outer Diameter Ratio
|
— | Head Diameter ≈ 1.5 × Screw Diameter (D_k ≈ 1.5D) |
|
Recessed Drive Type
|
— | Internal Hexagon (Allen) or Hexalobular (Torx) |
|
Standard Steel Property Class
|
— | High-tensile Class 12.9 (1,220 MPa) / Class 10.9 / Class 8.8 / A2-70 Stainless |
|
Primary Applications
|
— | Industrial tooling, machine tools, 3D printer extruders, automotive cylinder heads |