Description
ISO 7089 Plain Washer M4, A4 — BOLTON SKU 60111.
About the ISO 7089 Plain Washer M4 A4
This is a normal-series plain washer to ISO 7089 in the M4 size, produced in A4 austenitic stainless steel. The dimensions set by the standard are a 4.3 mm inside diameter, a 9 mm outside diameter and a nominal thickness of 0.8 mm, in product grade A, the closer-tolerance of the two grades the standard offers. Under an M4 screw head the washer provides a flat, parallel bearing face, stops the head from scoring or galling the assembled surface as it is tightened, and gives a modest increase in the diameter over which clamp load is distributed. Its thin 0.8 mm section is worth allowing for when calculating grip length on short screws, where a single washer can change thread engagement noticeably. The A4 material is the molybdenum-bearing grade within ISO 3506, giving better chloride resistance than A2 and keeping a stainless joint in a single material family.
Key specifications
| Standard | ISO 7089 (normal series, product grade A) |
|---|---|
| Nominal size | M4 |
| Inside diameter (d1) | 4.3 mm |
| Outside diameter (d2) | 9 mm |
| Thickness (h) | 0.8 mm nominal |
| Material | A4 austenitic stainless steel |
Typical applications
M4 plain washers are used throughout light mechanical and electro-mechanical assembly: enclosure and lid fixing, bracket and clamp mounting, cable-gland and connector hardware, and small equipment feet. At only 0.8 mm thick the washer adds little to the stack height, which matters where an M4 screw has limited length to work with. Choosing A4 suits outdoor, coastal and washdown enclosures, and any assembly in which A4 screws are already specified.
Supplied by BOLTON Technical Equipment Supplies against request for quotation. Add this item to your RFQ basket to request pricing, lead time and documentation requirements (e.g. CoC, datasheets or test reports where applicable).
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