Hexagon Head Bolts

Part threaded hexagon head bolts to ISO 4014 and DIN 931 in A2 (304) and A4 (316) stainless steel. A2 runs from M5 to M45 and A4 from M5 to M48, in lengths up to 500mm, and many A4 sizes come in both property class A4-70 and the stronger A4-80.

The plain, unthreaded shank under the head gives cleaner shear behaviour where it passes through the joint, which makes these the usual choice for steelwork, heavy timber and timber-to-metal joints. Use a fully threaded hex set screw for blind holes or thin material.

Frequently asked questions

What is a DIN 931 hex head bolt?

A DIN 931 hex head bolt has a hexagonal head and a shank that is only partly threaded, leaving a plain section directly under the head. ISO 4014 is the corresponding ISO standard; check the specified dimensions when replacing a DIN bolt. It is the standard hex bolt for joints where a smooth shank should sit in the shear plane. Simfix stocks them in A2 (304) and A4 (316) from M5 to M48.

DIN 931 vs DIN 933: what's the difference?

DIN 931 (ISO 4014) bolts have a plain, unthreaded shank under the head and threads only on the lower section. DIN 933 (ISO 4017) bolts, also called hex set screws, are threaded along the full shank. Use DIN 931 where the plain shank needs to sit in the shear plane, typically steelwork and timber-to-metal joints; use DIN 933 for blind holes or thin material.

What does A2-70 mean on a bolt?

A2 is the stainless steel grade (equivalent to 304); 70 is the property class, showing a minimum tensile strength of 700 MPa. So A2-70 means a 304 grade stainless bolt rated to at least 700 MPa before failure. Class 80, as in A4-80, means at least 800 MPa. Many Simfix A4 hex head bolts come in both A4-70 and A4-80.

What sizes of hex head bolt does Simfix stock?

A2 (304) from M5 to M45 and A4 (316) from M5 to M48, in lengths up to 500mm. Not every length is listed at every size and grade; check each product for current availability.

Sizes, grades and pack quantities vary by product type. Check the individual product listing for the exact specification and current availability.