Fasteners · ASME B18.2.1 · DIN 931 / 933 (legacy DIN)
Hex Bolt — ASME B18.2.1
Hex bolt — a bolt with a hexagonal head. Hex bolts join flanges, structures and equipment where one side is accessible for the head. Dimensions to ASME B18.2.1, or DIN 931 / 933 (legacy DIN) where an older specification calls for them.
- ASME B18.2.1
- 18 grades
- EN 10204 3.1 / 3.2
Reviewed by the Kanak Steel & Engineering Co. technical team · Updated October 2026
What is a hex bolt?
Short answer
A hex bolt is a bolt with a hexagonal head. Hex bolts join flanges, structures and equipment where one side is accessible for the head. Dimensions to ASME B18.2.1, or DIN 931 / 933 (legacy DIN) where an older specification calls for them.
Hex Bolt: What to Know Before Ordering
- Partially or fully threaded
- ASME B18.2.1 / DIN 931 / DIN 933
- Supplied with nuts and washers
Hex Bolt Materials & Grades
| Grade | Material standard | Best for |
|---|---|---|
| Inconel 825 hex bolt | Finished fastener specification not asserted; may be machined from ASTM B425 bar (UNS N08825), where applicable; finished fastener requirements are to the purchase specification or project drawing | Sulphuric and phosphoric acid service, chloride stress-corrosion cracking and sour gas |
| SS 904L hex bolt | Finished fastener specification not asserted; may be machined from ASTM A479 bar (UNS N08904), where applicable; finished fastener requirements are to the purchase specification or project drawing | Dilute sulphuric acid, phosphoric acid and chloride-bearing cooling water |
| SS 304 hex bolt | ASTM A193 B8 where specified; confirm grade and class in the purchase specification | General corrosion resistance, food, water and architectural work |
| SS 304L hex bolt | ASTM A193 B8 where specified; confirm grade and class in the purchase specification | Welded tanks, piping and vessels in general corrosive service |
| SS 310 / 310S hex bolt | Finished fastener specification not asserted; may be machined from ASTM A276 / A479 bar (UNS S31008), where applicable; finished fastener requirements are to the purchase specification or project drawing | Furnaces, burners and heat treatment at high temperature |
| SS 316 / 316L hex bolt | ASTM A193 B8M where specified; confirm grade and class in the purchase specification | Chloride-bearing process fluids, marine air and pharmaceutical service |
| SS 321 hex bolt | ASTM A193 B8T where specified; confirm grade and class in the purchase specification | High-temperature service between 425 and 815 °C |
| SS 347 hex bolt | ASTM A193 B8C where specified; confirm grade and class in the purchase specification | Welded high-temperature piping in refineries and power plants |
| Duplex 2205 hex bolt | ASTM A1082 (S32205) where specified; otherwise may be machined from ASTM A276 / A479 bar (UNS S32205), where applicable — finished requirements to the purchase specification or project drawing | Strength with chloride resistance at a stainless-steel budget |
| Super Duplex 2507 hex bolt | ASTM A1082 (S32750) where specified; otherwise may be machined from ASTM A276 / A479 bar (UNS S32750), where applicable — finished requirements to the purchase specification or project drawing | Seawater and high-chloride service where strength also matters |
| Inconel 600 hex bolt | Finished fastener specification not asserted; may be machined from ASTM B166 bar (UNS N06600), where applicable; finished fastener requirements are to the purchase specification or project drawing | High-temperature oxidation, caustic and nuclear service |
| Inconel 625 hex bolt | ASTM F468 (N06625) where specified, 0.250–1.500 in.; otherwise may be machined from ASTM B446 bar (UNS N06625), where applicable — finished requirements to the purchase specification or project drawing | Seawater, high strength and high temperature in one alloy |
| Inconel 718 hex bolt | ASTM A1014 (UNS N07718) where specified — product-type scope pending current standard text; otherwise may be machined from ASTM B637 bar (UNS N07718), where applicable — finished requirements to the purchase specification or project drawing | Very high strength at temperatures up to about 650 °C |
| Incoloy 800 / 800H / 800HT hex bolt | Finished fastener specification not asserted; may be machined from ASTM B408 bar (UNS N08800), where applicable; finished fastener requirements are to the purchase specification or project drawing | Furnaces, petrochemical heaters and high-temperature piping |
| Hastelloy C276 hex bolt | ASTM F468 (N10276) where specified, 0.250–1.500 in.; otherwise may be machined from ASTM B574 bar (UNS N10276), where applicable — finished requirements to the purchase specification or project drawing | The most aggressive mixed acids, wet chlorine and hypochlorite |
| Hastelloy C22 hex bolt | Finished fastener specification not asserted; may be machined from ASTM B574 bar (UNS N06022), where applicable; finished fastener requirements are to the purchase specification or project drawing | Mixed oxidising and reducing acids, and weld overlays |
| Monel 400 hex bolt | ASTM F468 (N04400) where specified, 0.250–1.500 in.; otherwise may be machined from ASTM B164 bar (UNS N04400), where applicable — finished requirements to the purchase specification or project drawing | Seawater, hydrofluoric acid and marine service |
| Monel K500 hex bolt | ASTM F468 (N05500) where specified, 0.250–1.500 in.; otherwise may be machined from ASTM B865 bar (UNS N05500), where applicable — finished requirements to the purchase specification or project drawing | High-strength pump shafts, bolting and springs in seawater |
Other fasteners
Stud boltA fully threaded rod supplied with two heavy hex nuts.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.Socket head cap screwA screw with a cylindrical head and hexagon socket.Machine screwA small-diameter screw for equipment assembly.
Hex bolt — questions buyers ask
What is a hex bolt?
A hex bolt is a bolt with a hexagonal head. Hex bolts join flanges, structures and equipment where one side is accessible for the head. Dimensions to ASME B18.2.1, or DIN 931 / 933 (legacy DIN) where an older specification calls for them.
DIN 931 or DIN 933?
DIN 931 bolts are partly threaded; DIN 933 are fully threaded.
Which grades are hex bolts 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 hex bolt dimensions?
ASME B18.2.1 · DIN 931 / 933 (legacy DIN). The material standard depends on the grade.
Reviewed by the technical team, Kanak Steel & Engineering Co.
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026
Sources: the ASTM / ASME specifications named on this page and producer datasheets · Last updated October 2026
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