A4 Stainless Steel Hexalobular Socket Head Cap Screws combine the dimensional form of ISO 14579 with the material properties of grade ISO 3506 group A4 (316 / 1.4401), commonly supplied A4-80: superior, including marine and chloride environments, largely non-magnetic, service range approx. -200 °C to +400 °C, subject to the property class and the joint. This page summarizes the grade data, its corrosion behavior in service, the comparable grades, and the sizes supplied.
Why Choose A4 Stainless Steel for Hexalobular Socket Head Cap Screws
Specified for marine, coastal and chemical applications. For hexalobular socket head cap screws, 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 |
Galvanic & Galling Considerations
Two important notes for stainless hexalobular socket head cap screws: (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.
Comparable Grades
For Hexalobular Socket Head Cap Screws, the alternative stainless grade is A2 (304). A2 (304) covers general indoor and outdoor service. A4 (316) adds molybdenum, which is what buys the chloride resistance for marine and de-icing-salt exposure. Where strength matters more than corrosion, plated alloy steel in class 8.8 or 10.9 is the swap to make.
Using Stainless Fasteners in Aluminum
Stainless steel is more noble than aluminum, so with an electrolyte present — rain, condensation, salt spray — the aluminum becomes the anode and corrodes at the joint. Area ratio decides how bad it gets: a small stainless fastener in a large aluminum section is normally acceptable, a large stainless fastener in thin aluminum is not. Where the joint gets wet, isolate the metals with a coated or nylon washer and a sealant, or specify an aluminum or coated fastener instead.
Sizes of Hexalobular Socket Head Cap Screws Available in A4 Stainless Steel
| Size | Drive size | A (mm) | t_mean (mm) | Length range l (mm) | Reference standard |
|---|---|---|---|---|---|
| M2 | T6 | 1.75 | 0.8 | 3~20 | ISO 14579 |
| M2.5 | T8 | 2.4 | 1.0 | 4~25 | ISO 14579 |
| M3 | T10 | 2.8 | 1.2 | 5~30 | ISO 14579 |
| M4 | T20 | 3.95 | 1.7 | 6~40 | ISO 14579 |
| M5 | T25 | 4.5 | 1.9 | 8~50 | ISO 14579 |
| M6 | T30 | 5.6 | 2.3 | 10~60 | ISO 14579 |
| M8 | T45 | 7.95 | 3.2 | 12~80 | ISO 14579 |
| M10 | T50 | 8.95 | 3.8 | 16~100 | ISO 14579 |
| M12 | T55 | 11.35 | 5.0 | 20~120 | ISO 14579 |
| (M14) | T60 | 13.45 | 5.8 | 25~140 | ISO 14579 |
| M16 | T70 | 15.7 | 6.8 | 25~160 | ISO 14579 |
| (M18) | T80 | 17.75 | 7.8 | 30~180 | ISO 14579 |
| M20 | T90 | 20.2 | 9.0 | 30~200 | ISO 14579 |
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. 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.
