Socket Head Cap (SHCS)
Direct Answer
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.
Source: DIN 912 / ISO 4762 / ASME B18.3 / ISO 898-1
Specs
| Standard Specifications | ISO 4762 / DIN 912 / ASME B18.3 |
| Head Geometry | Tall cylindrical head with knurled or smooth outer diameter |
| Head Height Ratio | Head Height $\approx$ Screw Major Diameter ($H \approx D$) |
| Head Outer Diameter Ratio | Head Diameter $\approx 1.5 \times$ Screw Diameter ($D_k \approx 1.5D$) |
| 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 |
High-Strength Counterbored Machine Design
Because the driving wrench inserts internally into the top of the head rather than clamping around the outside, machines do not need external side clearance for box wrenches. Designers drill cylindrical 'counterbores' into machine blocks, allowing high-strength Class 12.9 socket cap screws to sit completely flush with the surface of machine castings.
Standard Material Strengths
Unlike standard hardware-store machine screws (often mild Class 4.8 steel), socket head cap screws are manufactured by default from high-tensile chrome-molybdenum alloy steel heat-treated to Property Class 12.9, providing extreme yield strength up to 1,100 MPa (160,000+ psi).