Description
Plain Washer 4×9 A4 ISO 7089 — BOLTON SKU 56548.
About the Plain Washer 4×9 A4 ISO 7089
This is the M4 size of the ISO 7089 normal-series flat washer, supplied in A4 austenitic stainless steel. Per the standard, the M4 washer has a 4.3 mm clearance hole, a 9 mm outside diameter and a nominal thickness of 0.8 mm — the 4×9 figures in the designation. A4 is an acid-resistant stainless class used where hardware must survive chloride-bearing or persistently damp environments without plating. In service the washer spreads the clamp load of an M4 screw or nut, prevents the small head from digging into soft or thin material, and gives the joint a consistent bearing surface for repeatable torque. Product grade A indicates the tighter-tolerance grade of the standard, appropriate for controlled small-hardware assembly, and the same part doubles as a thin spacer or shim in M4 hardware stacks.
Key specifications
| Standard | ISO 7089 (plain washer, normal series, without chamfer) |
|---|---|
| Nominal size | M4 |
| Inside diameter (d1) | 4.3 mm |
| Outside diameter (d2) | 9 mm |
| Thickness (h) | 0.8 mm nominal (0.7–0.9 mm) |
| Material | A4 austenitic stainless steel |
| Cross-reference | DIN 125-1 Form A |
Typical applications
M4 A4 washers back small machine screws in electronics enclosures, panel hardware and light brackets, particularly where thin sheet or plastic would deform under a bare screw head. They are matched with A4 M4 screws and nuts so every element of the joint shares the same corrosion class.
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).
Browse more in MIL-Spec & Coded Fasteners.
Reviews
There are no reviews yet.