Socket Head Cap Screws

Socket head cap screws (SHCS), commonly called Allen bolts or socket cap screws, feature a cylindrical head with an internal hex drive. The recessed hex socket allows high installation torque in tight spaces and a clean, finished appearance. Machined from high-strength alloy steel and corrosion-resistant stainless, they are the standard for machine tools, dies, fixtures, and precision assemblies.

Why Socket Head Cap Screws

The internal hex drive delivers more torque than external-wrench fasteners of the same size and seats in counterbored holes for a flush or recessed finish. The small head diameter fits where hex heads cannot, and the deep socket resists cam-out, making SHCS ideal for high-strength, high-precision joints.

Grades and Materials

Alloy steel, Class 12.9 (or SAE J429 equivalent): the standard—through-hardened to roughly 170 ksi tensile, typically supplied with a black oxide or thermal black finish. 18-8 (A2) stainless: corrosion resistance for general environments. 316 (A4) stainless: superior resistance for marine and chemical exposure. Stainless socket screws are lower in strength than Class 12.9 alloy but far more corrosion resistant.

Dimensional Standards

Inch socket head cap screws conform to ASME B18.3. Metric versions follow DIN 912 / ISO 4762. Low-head variants follow DIN 7984. All use an internal hex (Allen) drive sized to the screw diameter.

Thread and Size Range

Stocked in coarse (UNC) and fine (UNF) inch threads and standard and fine metric pitches, in both partial and full thread. We carry sizes from miniature #0 and M1.6 up through 1-1/2" and M36, in lengths to match any grip requirement.

Selecting the Right Socket Head Cap Screw

Use Class 12.9 alloy for maximum strength in machine and tooling applications; choose stainless where corrosion resistance outweighs the need for peak tensile strength. Confirm the counterbore diameter and depth accommodate the head, verify thread pitch matches the tapped hole, and select the correct hex key size for installation. For vibration-prone joints, pair with thread-locking compound or a locking washer.

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