A574 Socket Head Cap Screws
The socket head cap screw specification: alloy steel quenched and tempered to 180 ksi in ½ in. and smaller and 170 ksi above, 37 to 44 HRC, black oxide — the standard for tooling, machinery and die work.
The workhorse of machine parts, die fixturing, and clamping. Standard socket head cap screws in alloy and stainless, imperial and metric, to ASME B18.3.
ASTM A574 covers alloy steel socket head cap screws in inch sizes: 180 ksi minimum tensile at ½ in. and smaller and 170 ksi above, with a 140 or 135 ksi proof load and a hardness of 37 to 44 HRC. The steel must be alloy, with 0.33 percent carbon minimum, and the screws are supplied bright or with a thermal or chemical black oxide finish unless a coating is ordered. Dimensions follow ASME B18.3.
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What A574 must meet.
| Grade / condition and size | Tensile strength, min (ksi) | Yield or proof, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| ½ in. and smaller (full size) | 180 | 140 proof | — | — | 39–44 HRC |
| Over ½ to 1 in. (full size) | 170 | 135 proof | — | — | 37–44 HRC |
| 1 in. and larger (machined specimen) | 170 | 153 yield | 10 | 35 | 37–44 HRC |
Values per ASTM A574-21 Table 1 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Quenched in oil from above the transformation temperature and tempered at 700 °F minimum (A574 clause 5.4). Screws through 0.625 in. diameter and 4 in. long are roll threaded unless otherwise specified; larger sizes are rolled, cut or ground at the manufacturer's option.
Full A574 data sheet: chemistry, physical properties and standards →
Made to standard or to your drawing.
- Tooling, dies and fixtures
- Machinery and machine-tool assembly
- Hydraulic manifolds and valve bodies
- High-strength fasteners in confined spaces