A2 Stainless Steel Square Head Bolts with Collar are supplied to DIN 478. The grade provides good general corrosion resistance and is largely non-magnetic; the practical service range is approx. -200 °C to +400 °C, subject to the property class and the joint. Property data, grade comparison and the full size table follow.
Why Choose A2 Stainless Steel for Square Head Bolts with Collar
The most common stainless group for indoor and general outdoor fasteners. For square head bolts with collar, 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 with Collar in indoor and general outdoor service. In chloride-bearing environments (marine air, road salt, swimming pools) consider stepping up to A4 (316).
Galvanic & Galling Considerations
Two important notes for stainless square head bolts with collar: (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 Square Head Bolts with Collar Available in A2 Stainless Steel
| Size | Pitch P (mm) | b1 (mm) | b2 (mm) | c (mm) | da (mm) | dc (mm) | Width across corners e (mm) | Head height k (mm) | r (mm) | Width across flats s (mm) | Length range l (mm) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 16 | 16 | 2 | 5.7 | 9.5 | 6.5 | 7 | 0.25 | 5 | 10~30 | DIN 478 |
| M6 | 1 | 18 | 18 | 2 | 6.8 | 10.5 | 8 | 8 | 0.25 | 6 | 10~40 | DIN 478 |
| M8 | 1.25 | 22 | 22 | 2 | 9.2 | 13.5 | 10 | 10 | 0.4 | 8 | 16~45 | DIN 478 |
| M10 | 1.5 | 26 | 32 | 3 | 11.2 | 16.5 | 13 | 13 | 0.4 | 10 | 20~60 | DIN 478 |
| M12 | 1.75 | 30 | 36 | 3 | 13.7 | 19.5 | 17 | 15 | 0.6 | 13 | 25~90 | DIN 478 |
| M16 | 2 | 38 | 44 | 4 | 17.7 | 25 | 22 | 20 | 0.6 | 17 | 30~140 | DIN 478 |
| M20 | 2.5 | 45 | 52 | 5 | 22.4 | 31 | 28 | 25 | 0.8 | 22 | 35~180 | DIN 478 |
| M24 | 3 | 54 | 60 | 6 | 26.4 | 36 | 32 | 28 | 0.9 | 24 | 35~180 | DIN 478 |
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. Thread size and pitch, length, property class, drive form, head geometry and head marking are all specifiable — the standard part is where it starts, not where it stops. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
