Socket Cap Screws

About Socket Cap Screws

Socket cap screws are high-strength fasteners featuring a cylindrical head with a hexagonal socket drive, designed for applications requiring superior holding power and a flush or low-profile finish. MyToolShed.co.uk stocks an extensive range of socket cap screws in various grades, materials and head styles, including socket head cap screws, button head screws, and countersunk variants. Available in premium grades such as 10.9 and 12.9 high-tensile steel, as well as A2 304 and A4 316 stainless steel options, these fasteners deliver exceptional performance in demanding environments.

Our collection features trusted brands including Sirius, Holo Krome, Sealey and Timco, with finishes ranging from black oxide and bright zinc plated (BZP) to self-colour and stainless steel. Whether you require metric, BSW or UNC thread specifications, MyToolShed stocks socket cap screws suitable for precision engineering, heavy machinery assembly, automotive applications and general fabrication work.

Applications

Socket cap screws are essential fasteners across numerous trades and industries:

• Engineering and Manufacturing: Machine assembly, precision equipment, robotics and CNC machinery
• Automotive and Motorsport: Engine components, chassis assembly, custom fabrication and performance modifications
• Construction and Fabrication: Structural steelwork, framework assembly and heavy-duty connections
• Maintenance Engineers: Equipment repair, replacement fasteners for industrial machinery
• Furniture Manufacturing: High-quality joinery requiring concealed or low-profile fixings
• Bicycle and Motorcycle Mechanics: Frame assembly, component mounting and precision adjustments
• DIY Enthusiasts: Home workshop projects, custom builds and restoration work

Choosing The Right Socket Cap Screws

Selecting appropriate socket cap screws requires consideration of several key factors:

• Grade and Strength: 10.9 grade offers excellent tensile strength for general applications, whilst 12.9 grade provides maximum strength for high-stress environments
• Head Style: Standard socket head cap screws for maximum strength, button head for lower profiles with larger bearing surfaces, or countersunk for completely flush finishes
• Material and Finish: Black oxide or self-colour for general engineering, BZP for corrosion resistance, A2 stainless for moderate environments, or A4 marine-grade stainless for harsh conditions
• Thread Type: Metric threads for standard UK applications, BSW (British Standard Whitworth) for older British machinery, or UNC (Unified National Coarse) for American equipment
• Size and Length: Ensure adequate thread engagement—typically 1.5 times the bolt diameter for steel, or 2 times for softer materials

Frequently Asked Questions

What size Allen key do I need for socket cap screws?

Socket cap screws use hexagonal Allen keys (hex keys), with the size depending on the screw diameter. Common sizes include 3mm for M4 screws, 4mm for M5, 5mm for M6, and 6mm for M8. Always verify the correct size before applying torque to avoid damaging the socket.

What's the difference between 10.9 and 12.9 grade socket cap screws?

The grade indicates tensile strength: 10.9 grade has a tensile strength of 1040 N/mm², whilst 12.9 grade offers 1220 N/mm². Grade 12.9 provides approximately 20% greater strength and is specified for high-stress applications, though 10.9 grade suffices for most general engineering purposes.

Can I use socket cap screws outdoors?

Yes, but material selection is critical. Standard black oxide or self-colour screws will corrode outdoors. Choose BZP for moderate protection, A2 stainless steel for general outdoor use, or A4-316 stainless steel for coastal or chemically aggressive environments.