A2 Stainless Steel Insulating Shoulder Washers are supplied to our own published dimensions — this is a trade-series article rather than one covered by a dimensional standard, so confirm the figures against the part you are replacing. 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.
Why Choose A2 Stainless Steel for Insulating Shoulder Washers
The most common stainless group for indoor and general outdoor fasteners. For insulating shoulder washers, 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 |
Galvanic & Galling Considerations
For stainless insulating shoulder washers the compatibility question is galvanic rather than galling: joined to aluminum or galvanized steel in wet service, stainless drives corrosion of the less-noble metal. Isolate with a coating, sleeve or non-conductive washer where the joint sees moisture. Note also that stainless is softer than hardened carbon steel, so where the part carries a wear or shear duty, check the load against the grade before substituting.
Comparable Grades
For Insulating Shoulder Washers, the alternative stainless grade is A4 (316). 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
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 Insulating Shoulder Washers Available in A2 Stainless Steel
| Screw size | Bore d1 (mm) | Shoulder outer diameter (mm) | Flange outer diameter d2 (mm) | Shoulder length (mm) | Flange thickness (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M2.5 | 2.7 | 3.6 | 6.0 | 1.5 | 0.8 | Industry standard |
| M3 | 3.2 | 4.2 | 7.0 | 1.5 | 0.8 | Industry standard |
| M3 | 3.2 | 4.2 | 7.0 | 3.0 | 0.8 | Industry standard |
| M4 | 4.3 | 5.4 | 9.0 | 2.0 | 1.0 | Industry standard |
| M4 | 4.3 | 5.4 | 9.0 | 3.5 | 1.0 | Industry standard |
| M5 | 5.3 | 6.6 | 11.0 | 2.5 | 1.0 | Industry standard |
| M6 | 6.4 | 7.8 | 13.0 | 3.0 | 1.2 | Industry standard |
Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in A2 Stainless Steel. The catalogue's default material column has been omitted here so it cannot be read as contradicting that.
Custom manufacturing · Made to drawing
Need this washer in a grade that is not listed?
A2 Stainless Steel is one of the grades the catalog describes. Bearing area is usually the reason for a special washer: a larger outside diameter to spread load into a softer material, or a thicker section to resist dishing. Made by stamping or punching.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
