For flanged button head socket cap screws, unc in A4 Stainless Steel, the controlling selection factors are corrosion exposure, strength requirement and service temperature. The grade data for A4 Stainless Steel (ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80) is summarized below together with every size supplied.
Why Choose A4 Stainless Steel for Flanged Button Head Socket Cap Screws, UNC
Specified for marine, coastal and chemical applications. For flanged button head socket cap screws, unc, this matters when superior, including marine and chloride environments is the primary requirement.
Mechanical & Physical Properties
| Grade designation | ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80 |
|---|---|
| Magnetic response | Largely non-magnetic |
| Service temperature | approx. -200 °C to +400 °C, subject to the property class and the joint |
| Corrosion characteristic | Superior, including marine and chloride environments |
Corrosion Behavior in Service
A4 (316) adds 2–3% molybdenum to the A2 (304) composition, which dramatically improves resistance to chloride-pitting corrosion. For Flanged Button Head Socket Cap Screws, UNC in marine, coastal, swimming-pool or food-processing environments, A4 is the default selection.
Galvanic & Galling Considerations
Two important notes for stainless flanged button head socket cap screws, unc: (1) stainless can gall on stainless threads under load — use a thread lubricant or anti-galling compound, especially for M6 and below; (2) when joined to aluminum or galvanized steel, stainless can drive galvanic corrosion of the less-noble metal in wet service — isolate with a coating or sleeve where appropriate.
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 A4 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 A4 Stainless Steel.
Custom manufacturing · Made to drawing
Need this screw in a grade that is not listed?
A4 Stainless Steel is one of the grades the catalog describes. Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
