A4 Stainless Steel Insulating Fibre 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 superior, including marine and chloride environments 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 A4 Stainless Steel for Insulating Fibre Washers
Specified for marine, coastal and chemical applications. For insulating fibre washers, 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
For stainless insulating fibre 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 Fibre Washers, the alternative stainless grade is A2 (304). The practical dividing line is chlorides: A2 (304) is fine until salt is involved, and A4 (316) exists for the cases where it is — coastal, marine and road-salt service. Neither reaches the strength of a plated class 8.8 or 10.9 fastener.
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 Insulating Fibre Washers Available in A4 Stainless Steel
| For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Dielectric strength (kV/mm) | Max temperature (°C) | Moisture |
|---|---|---|---|---|---|---|
| M3 | 3.2 | 7.0 | 0.5 | 10 | 105 | Hygroscopic — indoor use |
| M4 | 4.3 | 9.0 | 0.5 | 10 | 105 | Hygroscopic — indoor use |
| M5 | 5.3 | 10.0 | 0.8 | 10 | 105 | Hygroscopic — indoor use |
| M6 | 6.4 | 12.0 | 0.8 | 10 | 105 | Hygroscopic — indoor use |
| M8 | 8.4 | 16.0 | 1.0 | 10 | 105 | Hygroscopic — indoor use |
| M10 | 10.5 | 20.0 | 1.0 | 10 | 105 | Hygroscopic — indoor use |
Dimensions are independent of the material: the table above lists the sizes supplied, and on this page every one of them is quoted in A4 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?
A4 Stainless Steel is one of the grades the catalog describes. Bore, outside diameter, thickness, temper and finish are the variables here — there is no thread to specify, so the fit and the bearing area are what the drawing has to pin down. Made by stamping or punching.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
