Fasteners · ASME B18.3 · DIN 912 / ISO 4762
Socket Head Cap Screw — ASME B18.3
Socket head cap screw — a screw with a cylindrical head and hexagon socket. Allen-type cap screws are used where the head must sit flush or space is tight.
- ASME B18.3
- 18 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
Socket Head Cap Screw: What to Know Before Ordering
- Hex socket drive
- ASME B18.3 · DIN 912
- Metric and inch
Socket Head Cap Screw Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 socket head cap screw | ASTM B425 | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L socket head cap screw | ASTM B649 | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 socket head cap screw | ASTM A193 B8 · A194 8 | General corrosion resistance, food, water and architectural work |
| SS 304L socket head cap screw | ASTM A193 B8 · A194 8 | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S socket head cap screw | ASTM A276 / A479 | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L socket head cap screw | ASTM A193 B8M · A194 8M | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 socket head cap screw | ASTM A193 B8T | High-temperature service between 425 and 815 °C |
| SS 347 socket head cap screw | ASTM A193 B8C | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 socket head cap screw | ASTM A276 / A479 | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 socket head cap screw | ASTM A276 / A479 | Seawater and high-chloride service where strength also matters |
| Inconel 600 socket head cap screw | ASTM B166 | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 socket head cap screw | ASTM B446 | Seawater, high strength and high temperature in one alloy |
| Inconel 718 socket head cap screw | ASTM B637 | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT socket head cap screw | ASTM B408 | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 socket head cap screw | ASTM B574 | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 socket head cap screw | ASTM B574 | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 socket head cap screw | ASTM B164 | Seawater, hydrofluoric acid and marine service |
| Monel K500 socket head cap screw | ASTM B865 | High-strength pump shafts, bolting and springs in seawater |
Other fasteners
Stud boltA fully threaded rod supplied with two heavy hex nuts.Hex boltA bolt with a hexagonal head.Heavy hex nutA thicker and wider hexagon nut for pressure bolting.Hex nutA standard hexagon nut.WasherA flat or spring ring that spreads bolt load.Threaded rodA continuously threaded bar cut to length.U-boltA U-shaped bolt for clamping pipes to supports.Eye boltA bolt with a loop head for lifting or anchoring.Anchor boltA bolt that fixes structures or equipment to concrete.Foundation boltA heavy bolt set in concrete for machinery bases.Machine screwA small-diameter screw for equipment assembly.
Socket head cap screw — questions buyers ask
DIN 912 and ISO 4762 — are they the same?
Yes, ISO 4762 replaced DIN 912 with the same main dimensions.
Which grades are socket head cap screws available in?
Inconel 825, SS 904L, SS 304, SS 304L, SS 310 / 310S, SS 316 / 316L, SS 321, SS 347, Duplex 2205, Super Duplex 2507, Inconel 600, Inconel 625, Inconel 718, Incoloy 800 / 800H / 800HT, Hastelloy C276, Hastelloy C22, Monel 400, Monel K500.
Which standard covers socket head cap screw dimensions?
ASME B18.3 · DIN 912 / ISO 4762. The material standard depends on the grade.
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