Material specification page for flanged button head socket 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 B18.3.
Why Choose A2 Stainless Steel for Flanged Button Head Socket Cap Screws, UNC
The most common stainless group for indoor and general outdoor fasteners. For flanged button head socket 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 Flanged Button Head Socket 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 Flanged Button Head Socket 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
Expect the aluminum to corrode, not the fastener — stainless sits higher in the galvanic series, so the aluminum is the one that gives up material. A small fastener in a thick section spreads the loss over a large area and is usually fine; a large fastener in thin sheet concentrates it and is not. Keep water out of the joint, or isolate the two metals with a nylon or coated washer and a sealant.
Sizes of Flanged Button Head Socket Cap Screws, UNC Available in A2 Stainless Steel
| Size | Pitch P (mm) | b (mm) | c (mm) | Head diameter dk (mm) | dk_c (mm) | Hex socket s (mm) | t (mm) | r (mm) | Head height k (mm) | Length range l (in) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|---|
| #2 | 0.454 | 8.738 | 0.437 | 3.604 | 4.775 | 1.27 | 1.529 | 0.109 | 1.201 | 1/16"~1" | ASME B18.3 |
| #4 | 0.635 | 11.379 | 0.569 | 4.694 | 5.944 | 1.587 | 1.991 | 0.142 | 1.565 | 1/8"~2" | ASME B18.3 |
| #6 | 0.794 | 14.021 | 0.701 | 5.784 | 7.544 | 1.984 | 2.454 | 0.175 | 1.928 | 1/8"~3" | ASME B18.3 |
| #8 | 0.794 | 16.662 | 0.833 | 6.873 | 9.119 | 2.381 | 2.916 | 0.208 | 2.291 | 1/8"~3" | ASME B18.3 |
| #10 | 1.058 | 19.304 | 0.965 | 7.963 | 10.312 | 3.175 | 3.378 | 0.241 | 2.654 | 3/16"~3" | ASME B18.3 |
| 1/4" | 1.27 | 25.4 | 1.27 | 10.477 | 14.3 | 3.969 | 4.445 | 0.318 | 3.493 | 3/16"~4" | ASME B18.3 |
| 5/16" | 1.411 | 31.75 | 1.587 | 13.097 | 17.475 | 4.763 | 5.556 | 0.397 | 4.366 | 1/4"~4" | ASME B18.3 |
| 3/8" | 1.587 | 38.1 | 1.905 | 15.716 | 20.65 | 5.556 | 6.668 | 0.476 | 5.239 | 1/4"~5" | ASME B18.3 |
| 1/2" | 1.954 | 50.8 | 2.54 | 20.955 | 29.362 | 7.938 | 8.89 | 0.635 | 6.985 | 1/2"~5" | ASME B18.3 |
Dimensions are independent of the material: every size above is available in A2 Stainless Steel.
Custom manufacturing · Made to drawing
Need this screw 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 warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
