Material specification page for square-head bolts in A2 Stainless Steel. Covers the grade designation (ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70), corrosion and magnetic behavior, comparable grades and their trade-offs, and the sizes available to ASME B18.2.1 / SAE J429 Grade 5.
Why Choose A2 Stainless Steel for Square-Head Bolts
The most common stainless group for indoor and general outdoor fasteners. For square-head bolts, this matters when good general corrosion resistance is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A2 (304 / 1.4301), commonly supplied A2-70 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Good general corrosion resistance |
Corrosion Behavior in Service
A2 (304) gives excellent atmospheric and most-water corrosion resistance and is the most common stainless for Square-Head Bolts in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Comparable Grades
For Square-Head Bolts, the alternative stainless grade is A4 (316). Choose A2 (304) for general use and A4 (316) wherever chlorides are present; the molybdenum in A4 is the whole difference. Remember that stainless is the corrosion answer, not the strength answer — for load, look at class 8.8 or 10.9 instead.
Using Stainless Fasteners in Aluminum
The galvanic couple here runs the wrong way: aluminum is the less noble metal, so it corrodes and the fastener does not. What governs the rate is the ratio of areas — a large anode and a small cathode is a tolerable combination, the reverse concentrates the attack into thin material around the hole. An isolating washer plus sealant breaks the circuit; where that is impractical, match the fastener to the substrate.
Sizes of Square-Head Bolts Available in A2 Stainless Steel
| Size | Thread form | Head width (in) | Head height (in) | Tensile strength (psi) | Material / grade | Reference standard |
|---|---|---|---|---|---|---|
| 1/4-20 | fully or partially threaded | 3/8 | 11/64 | 120000 | yellow-zinc-chromate steel, Grade 5 | ASME B18.2.1 / SAE J429 |
| M6 / M8 / M10 / M12 / M14 / M16 / M20 / M24 / M30 | fully or partially threaded | yellow-zinc-chromate steel, Grade 5 | ASME B18.2.1 / SAE J429 | |||
| 5/16-18 through 1-1/4-7 | fully or partially threaded | yellow-zinc-chromate steel, Grade 5 | ASME B18.2.1 / SAE J429 |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this bolt in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
