Material specification page for hex flange head cap screws, unc 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.
Why Choose A2 Stainless Steel for Hex Flange Head Cap Screws, UNC
The most common stainless group for indoor and general outdoor fasteners. For hex flange head cap screws, unc, 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 Hex Flange Head Cap Screws, UNC 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 Hex Flange Head Cap Screws, UNC, 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 Hex Flange Head Cap Screws, UNC Available in A2 Stainless Steel
| Size | b0 (mm) | Pitch P (mm) | c (mm) | dc (mm) | kw (mm) | r1 (mm) | Width across flats s (mm) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|
| 1/4" | 19.05 | 1.27 | 0.953 | 14.287 | 2.857 | 0.318 | 9.525 | 3/8"~4" | ASME B18.2.1 |
| 5/16" | 22.225 | 1.411 | 1.191 | 17.462 | 3.572 | 0.397 | 12.7 | 1/2"~4" | ASME B18.2.1 |
| 3/8" | 25.4 | 1.587 | 1.429 | 20.637 | 4.286 | 0.476 | 14.287 | 1/2"~5" | ASME B18.2.1 |
| 7/16" | 28.575 | 1.814 | 1.667 | 23.812 | 5.001 | 0.556 | 15.875 | 3/4"~5" | ASME B18.2.1 |
| 1/2" | 31.75 | 1.954 | 1.905 | 27.384 | 5.715 | 0.635 | 19.05 | 3/4"~6" | ASME B18.2.1 |
| 5/8" | 38.1 | 2.309 | 2.381 | 33.734 | 7.144 | 0.794 | 23.812 | 1"~6" | ASME B18.2.1 |
| 3/4" | 44.45 | 2.54 | 2.857 | 40.481 | 8.572 | 0.953 | 28.575 | 1"~6" | ASME B18.2.1 |
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.
