Countersunk vs. Socket Head Cap
Comparing 2 standards across 12 specifications. 12 key differences identified.
Flat Head (Countersunk / CSK, standardized under ISO 7046 and DIN 965) screws feature a flat top face and a conical tapered underside (90° in ISO Metric, 82° in US Imperial, 100° in Aerospace). Designed to seat inside a matching chamfered hole, the head sits 100% flush with or slightly below the surface of the joined material.
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 7046 / DIN 965 / ASME B18.6.3 | ISO 4762 / DIN 912 / ASME B18.3 |
|
Primary Applications
|
Woodworking, door hinges, machine slides, aircraft aerodynamic skin | Industrial tooling, machine tools, 3D printer extruders, automotive cylinder heads |
|
Head Top Profile
|
100% Flat top face | — |
|
Countersink Angle (ISO Metric / DIN)
|
90 degrees | — |
|
Countersink Angle (US Imperial / ASME)
|
82 degrees | — |
|
Countersink Angle (Aerospace / NAS)
|
100 degrees (for thin structural aircraft skins) | — |
|
Length Measurement Rule
|
Overall Length (Measured from top of head to screw tip) | — |
|
Head Geometry
|
— | Tall cylindrical head with knurled or smooth outer diameter |
|
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 |