Form A Washers (DIN 125-A / BS 4320)

Standard flat Form A washers in zinc and stainless steel for load spreading, clamping and spacing applications.

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Form A Washer - Stainless Steel

Form A Washer - Stainless Steel (13)

Form A Washer - Zinc

Form A Washer - Zinc (27)

Form A washers are flat washers used to spread load under a bolt head or nut. They help protect the surface, reduce pull-through and improve clamping performance in timber, steel and general construction work.

These washers follow common metric standards such as DIN 125-A and BS 4320 and are one of the most widely used washer types in fixings and fasteners.

Available sizes by finish

Our Form A washer range is available in the following sizes in zinc and stainless steel:

Washer size Zinc Form A Stainless Steel Form A
M4 ✓ ✓
M5 ✓ ✓
M6 ✓ ✓
M8 ✓ ✓
M10 ✓ ✓
M12 ✓ ✓
M14 ✓ ✕
M16 ✓ ✓
M20 ✓ ✕
M24 ✓ ✕

How do I choose the correct washer size?

Match the washer size to the bolt diameter. For example, use an M10 washer with an M10 bolt. This keeps the washer centred on the shank and allows it to spread the load evenly.

Check that the washer covers enough surface around the hole without overhanging too far. For heavier loads or softer materials, a larger outer diameter washer such as Form B or a mudguard washer may be a better choice.

Zinc vs stainless steel Form A washers

Feature Zinc Form A washers Stainless steel Form A washers
Material Carbon steel with zinc plating A2 stainless steel
Corrosion resistance Low. Best suited to dry internal environments. High. Suitable for external, damp and coastal environments.
Typical use General internal construction and workshop use. Outdoor fixings, treated timber, green oak and marine use.
Standards DIN 125-A BS 4320 and DIN 125-A

Zinc plated washers are a good choice for clean, low humidity internal work. Stainless steel washers are the better option where moisture, weather or corrosive materials are present and where long-term corrosion resistance is important.

Frequently asked questions

How do I know if I need stainless instead of zinc?
Choose stainless steel if the fixing is outdoors, in a damp area or in contact with treated timber, green oak or other corrosive materials. Zinc is usually fine for dry internal environments.

Are Form A washers suitable for structural work?
Form A washers are used in many structural applications, but you should always follow engineer or manufacturer guidance on washer type, size and material for critical fixings.

What is the difference between Form A and Form B washers?
Form A washers have a standard outer diameter. Form B washers have a larger outer diameter for increased load spreading where the surface is softer or the load is higher.

For washers with a larger outer diameter for improved load distribution, see our Form B and Form C washer ranges.

Looking for other washer types? Explore our full washer range, including Form B, Form C, penny repair washers, spring washers and square plate washers.