Hexagon socket cap screw

What is a Socket Cap Screw?

A Socket Cap Screw features a cylindrical head with a deep internal hexagonal drive. It is typically used in machine parts, die fixturing, and clamping. The most significant advantage of this design is space efficiency. Because the tightening tool (Allen key) is inserted into the head rather than around it, these screws can be placed very close together or counter-bored so the head is flush with the surface.

Material Selection Guide

We categorize our socket screws into two primary material groups based on your environmental needs: Stainless Steel (A2 & A4): Ideal for outdoor, marine, or food-processing environments. Grade 304 (A2) is the standard for general corrosion resistance, while Grade 316 (A4) offers superior protection against salt and chemicals. Stainless socket screws generally have a lower tensile strength (Class 70) than high-tensile carbon steel. Carbon Steel (8.8, 10.9, 12.9): Chosen for their immense strength. Grade 12.9 is the standard for carbon steel socket caps, offering the highest tensile strength (1200 MPa) for critical load-bearing applications. These are typically supplied in a black oxide or zinc-plated finish.

Head Style: Knurled vs. Plain

You will find two head variations in our catalog:

• Knurled Head: Features a textured pattern on the side of the cylindrical head. This provides grip for fingers, allowing for faster manual insertion before final tightening with a tool.
• Plain (Smooth) Head: Features a smooth cylindrical side. This is often preferred for aesthetic reasons or applications where the head must fit precisely into a counter-bored hole with minimal clearance.

Quality Assurance

Fastener Core delivers reliability. An EN 10204 3.1 Material Certificate is available upon request to verify the chemical composition and mechanical properties of your batch. Please note that third-party inspection services are available for an additional fee.

Common Applications

Socket cap screws are ubiquitous in modern engineering:

• Machine Tooling: Fastening dies, molds, and precision guides where high clamp force is needed.
• Automotive: Engine components and intake manifolds where wrench access is restricted.
• Electronics: Assembly of consumer device casings and robotics.
• Furniture: "Flat-pack" furniture assembly due to the safety and flush-finish of the head.

Frequently Asked Questions

What is the standard grade for black socket cap screws?

The industry standard for plain black (self-color) carbon steel socket cap screws is Grade 12.9. This is the strongest standard fastener grade, offering extreme tensile strength. However, we also supply Grade 8.8 and 10.9 upon request for less critical applications.

Do I need washers with socket cap screws?

It depends on the surface material. Because the bearing area under the head of a socket screw is smaller than a hex bolt, it exerts high pressure. If fastening into soft materials like aluminum or plastic, a washer is highly recommended to prevent the head from sinking into the surface.

Are knurled heads more expensive?

Generally, the price difference is negligible. The choice between knurled and plain heads usually comes down to preference or the specific manufacturing standard of the brand in stock. Knurling is primarily a feature to aid hand-tightening efficiency.