Socket Head Cap Screws

Socket Head Cap Screw Grade & Material — Quick Reference

Socket head cap screws (SHCS) are the workshop standard for precision fastening — internal hex (Allen) drive, high tensile strength, available across grades + materials. Selection turns on load (Grade 8.8 / 10.9 / 12.9 / Bumax for high-strength), corrosion environment (zinc/black oxide/SS304/SS316/Bumax), and size (M3 – M30+ metric).

Critical: Match the bolt grade to the application — overuse of 12.9 in soft material = no benefit, just cost. Use the right Allen key size (M5 = 4mm hex, M6 = 5mm, M8 = 6mm, M10 = 8mm, M12 = 10mm). Brands: Bremick, Hobson, Champion, GJ Works, Inox World, SOKO, Bumax. Companion: fasteners, torque chart, SHCS guide, bolt grade chart.

Socket Head Cap Screws in Steel, Stainless and Bumax from Bremick, Hobson, Inox World and SOKO

AIMS Industrial sells an extensive range of socket head cap screws from Bremick, Hobson, Champion, GJ Works, Inox World, SOKO and Bumax — metric Allen key cap screws in black oxide steel, zinc-plated steel, 304 stainless steel, Grade 316 marine stainless steel and high-strength Bumax for precision engineering, machine building, industrial equipment assembly and corrosion-resistant fastening applications.

Brands in This Range

• Bremick: Bremick is an Australian fastener distributor supplying a comprehensive range of metric socket head cap screws in black and zinc-plated finishes for general engineering and industrial applications.
• Hobson: Hobson is a leading Australian fastener supplier distributing socket head cap screws in multiple grades and materials for industrial and engineering use.
• Inox World: Inox World specialises in Grade 316 marine-grade stainless steel fasteners. Inox World socket head cap screws are specified for marine, coastal, food processing and chemical plant applications.
• SOKO: SOKO supplies metric socket head fasteners for industrial and engineering fastening applications, providing cost-effective standard-grade socket head cap screws in commonly specified sizes.
• Bumax: Bumax is a Swedish manufacturer of ultra-high-strength stainless steel fasteners. Bumax socket head cap screws achieve tensile strengths comparable to or exceeding standard high-tensile steel fasteners while providing the corrosion resistance of austenitic stainless steel — specified for demanding applications in oil and gas, defence, subsea and critical engineering.

Materials and Grades

• Black Oxide Steel (Property Class 12.9): The standard specification for socket head cap screws in engineering applications. Class 12.9 provides high clamping force and is used in machine building, tooling and precision engineering where high joint preload is required.
• Zinc-Plated Steel: Moderate corrosion resistance for indoor and protected environments. Suitable for general industrial and workshop assembly where black oxide appearance is not required.
• 304 and 316 Stainless Steel: 304 stainless provides general corrosion resistance. Grade 316 is specified for marine, coastal, chemical and food processing environments. Stainless socket head cap screws are lower strength than Class 12.9 steel — not a like-for-like substitution in high-stress applications.

Expert Support: Need help buying the right product for your application? Contact our team for application-specific advice or request a quote.

Australian Business, Local Supply: As a proudly Australian business since 1988, we supply precision fasteners and engineering hardware from trusted brands to trade and industrial customers across Australia.

Also see our hex bolts, nuts, spring washers, self drilling screws and fasteners & fixings ranges for more complementary products.

People Also Ask — Socket Head Cap Screws

Q: What's the standard grade of socket head cap screws?

Grade 12.9 (ISO 898-1) is the standard for socket head cap screws — high-tensile, suitable for engineering and machinery applications. Stainless socket head cap screws are typically A2-70 (304 stainless) or A4-70 (316 stainless) per ISO 3506. The grade is stamped on the head. Lower grades (8.8, A2-50) are used in lighter applications. Always match the grade to the application's load requirements.

Q: What hex key size matches my socket head cap screw?

Standard metric: M3 = 2.5mm, M4 = 3mm, M5 = 4mm, M6 = 5mm, M8 = 6mm, M10 = 8mm, M12 = 10mm, M16 = 14mm, M20 = 17mm. Imperial Allen key sizes match imperial screws (1/8 inch hex = 1/4 inch screw etc). The hex socket should fit snugly — wear or rounding in the socket usually means the wrong hex key has been used or the screw has been over-torqued.

Q: Why use a socket head cap screw over a hex head bolt?

Socket head cap screws have a cylindrical head that sits in a counterbore — flush or recessed with the surface for aesthetic or clearance reasons. Hex head bolts have heads protruding above the surface for wrench access. Socket heads work better in tight spaces (no wrench clearance needed), in counterbored applications (engineered for the bore), and where appearance matters. They also typically have higher tensile strength than equivalent hex bolts in the same size.

Q: What's the difference between cap screw and button head?

Standard cap screws have tall cylindrical heads with a hex socket (high-strength, full grip area). Button head screws have a rounded dome head with hex socket (lower profile, less strength than cap screws because of the shorter head height). Low-head cap screws sit between the two — shorter than full cap, taller than button. Use full cap screws for strength-critical applications; button heads for aesthetic or low-profile applications.

Q: What torque should I tighten a socket head cap screw to?

Torque depends on grade, size, material, and joint design — published torque charts cross-reference these inputs. For workshop guidance: M6 grade 12.9 typically 13 Nm, M8 = 33 Nm, M10 = 65 Nm, M12 = 115 Nm. These are baseline values assuming clean dry threads — lubricated threads reduce target torque by about 15-20% to achieve the same clamp force. For critical applications, use a calibrated torque wrench.