A2 Stainless Penny Washers DIN 9021

A2 stainless steel penny washers (also known as mudguard washers, fender washers or repair washers), manufactured to DIN 9021 (Form G, now superseded by ISO 7093 with the same dimensions) - large-diameter flat washers with an outer diameter roughly three times the nominal bolt size, built to spread clamping load over a far wider area than a standard flat washer can manage.

The defining feature is that oversized bearing surface: where a standard washer's smaller outer diameter risks letting a bolt head or nut pull straight through - or simply crush - a soft or thin surface, the penny washer's wide face distributes the same clamping force across a much larger footprint. That makes it the natural choice for fixing into timber, plastic, sheet metal, rubber and composite materials, and for bridging fixing holes that have become oversized, elongated or slightly irregular through wear, rust or a previous repair. It's also useful wherever the fixing hole is oversized or slightly irregular, since the wide washer bridges the gap reliably.

Manufactured in A2 stainless steel (equivalent to 18-8), these washers offer long-lasting corrosion resistance, even in harsh weather conditions, making them suitable for outdoor exposure and general engineering use.

Key Features

• Manufactured to DIN 9021 (Form G), dimensionally equivalent to the current ISO 7093 standard
• A2 stainless steel (18-8 equivalent) for strong, long-lasting general corrosion resistance
• Outer diameter roughly three times the nominal thread size, for maximum load-spreading compared with a standard flat washer
• Nine thread sizes covering the full M2 to M16 range, from small precision fixings up to heavy-duty bolts
• Wide, flat bearing face suited to soft, thin or easily-damaged materials - timber, plastic, sheet metal, rubber and composites
• Bridges oversized, elongated or slightly irregular fixing holes that a standard washer would not fully cover
• Consistent proportions across the size range, so the same wide-bearing benefit applies whether you're working with M2, M16 or M8 penny washers
• Also known as a mudguard washer, widely used for automotive and vehicle bodywork repair
• Easy to fit, speeding up construction and repair work

Specification

• Material: A2 stainless steel (equivalent to 18-8)
• Standard: DIN 9021 (Form G), dimensionally equivalent to ISO 7093
• Design: Large outer diameter (~3× nominal bolt size) for wide load distribution

Sizes

The table below lists the inner diameter (d1), outer diameter (d2) and thickness (h) for each thread size, with the outer diameter also given in inches for quick reference against imperial fixings.

Typical Applications

Penny washers earn their "mudguard washer" nickname from vehicle bodywork repair, where they're used to repair rusted, enlarged or elongated fixing holes on mudguards, wings and other bodywork panels on cars, trailers and agricultural machinery - the wide face bridges the damaged area cleanly instead of trying to fix a fresh, smaller washer over a hole it can't fully cover. The same load-spreading principle carries over into general fixing work:

• Fixing into timber, plastic, sheet metal, rubber or composite panels, where a standard washer would risk pulling through or crushing the surface under load
• Covering oversized, worn or slightly irregular fixing holes left by a previous repair, corrosion, or an incorrectly sized pilot hole
• General engineering, construction, industry, woodworking and maintenance assembly work requiring a wide-bearing, corrosion-resistant washer
• Outdoor and exposed fixings on gates, fencing and garden structures, where the A2 stainless steel's corrosion resistance keeps the fixing sound long term
• Trailer and agricultural equipment repair, from bodywork panels to guard and panel fixings

Installation Guidance

Match the washer's inner diameter to the bolt or screw shank for a snug, non-loose fit rather than sizing up unnecessarily. When covering an enlarged, elongated or irregular hole, centre the washer so its full bearing face sits over sound material on both sides of the hole before tightening down - this spreads the clamping load evenly across the wide diameter rather than concentrating it at one edge, which is the whole point of fitting a penny washer in place of a standard one. On a bodywork repair, check the washer fully bridges the damaged area on the outer face before you tighten the fixing down, since it's this outer coverage that stops the joint working loose again through the enlarged hole.

Common Questions

Which size do I need?
Match the inner diameter (d1) to your bolt or screw: for example, an M5 washer has a 5.3mm (0.21in) hole for an M5 fixing. All nine sizes, with outer diameter and thickness, are in the table above.

Can I use them outdoors?
Yes. A2 stainless steel gives long-lasting corrosion resistance, even in harsh weather conditions, for gates, fencing, garden structures, trailers and vehicle bodywork.

Will one cover an enlarged or elongated hole?
Yes, when its outer diameter reaches past the damage: centre the washer so its full bearing face sits over sound material on both sides of the hole, then tighten.

Do they match ISO 7093?
Sizes M3 to M16 have the same inner and outer diameters (d1 and d2) as ISO 7093.