A penny washer is a flat washer with an unusually large outside diameter compared to its hole size — and that extra metal is the whole point. The name comes from the old pre-decimal penny coin, which the washer's face roughly resembled, and the oversized face is what makes penny washers the go-to fixings for spreading load, covering oversized or damaged holes, and bolting through soft materials.
What does a penny washer actually do?
Three jobs, all down to that big flat face:
- Spread the load. A bolt tightened onto a small washer can pull through soft timber, plastic or thin sheet. A penny washer's wide face distributes the clamping force over a much bigger area — think coach screws into softwood, or fixing brackets to plywood.
- Cover oversized or damaged holes. If a hole has been drilled too big, worn into a slot, or torn out by a previous fixing, a penny washer bridges it and lets the bolt still do its job. This is the classic "repair washer" use, and it's why the two names get used interchangeably.
- Give a clean seating surface. On uneven or rough faces, the large flat bearing area stops the bolt head or nut from rocking and loosening.
Penny washer sizes: what we stock
Our range runs M5 to M12 in hole size, with outside diameters from around 20mm up to 50mm, in two finishes:
- Zinc plated — the everyday choice for general trade and indoor work.
- A2 stainless steel — for outdoor and damp environments, or anywhere appearance matters alongside corrosion resistance.
Common picks by hole size:
| Hole size | Typical ODs stocked | Typical use |
|---|---|---|
| M5 | 20–25mm | Small brackets, electrical and light fittings |
| M6 | 20–50mm | General trade work, repair duty on small fixings |
| M8 | 25–50mm | Gate hardware, timber structures |
| M10 | 25–50mm | Heavy brackets, structural timber |
| M12 | 38–50mm | Heavy-duty load spreading |
The rule for repair work: the outside diameter should comfortably cover the damaged hole with margin to spare — if it only just overlaps, the load can still pull through the weakened edge.
Penny washer vs standard flat washer — when does the big one matter?
A standard flat washer is sized to suit the bolt in normal duty. Step up to a penny washer when any of these apply:
- Soft base material — timber, ply, plastic or GRP where a normal washer might pull through.
- Slotted or oversized holes — the extra face bridges what a standard washer can't.
- Big bolt heads or nuts on thin material — more bearing area means less embedding and less loosening.
- Weather sealing over a wider footprint — pairing with a sealing washer where water is in play.
For the full family — form A washers, shakeproof, and the rest — see our guide to the washers we stock.
Which material: zinc plated or stainless?
- Zinc plated penny washers for general indoor and sheltered outdoor use — the cost-effective default.
- A2 stainless penny washers for outdoor exposure, coastal jobs, treated timber and anywhere the washer will be visible on finished work. Stainless is the usual call alongside stainless bolts to avoid mixed-metal corrosion.
Ordering penny washers from Fastco
The full M5–M12 range in zinc plated and A2 stainless is on our penny washers category page — fast UK delivery, no account needed to order. If you're matching a washer to a specific bolt or repairing an oversized hole and want a second opinion, speak to an expert on 01270 252 326 (Monday–Friday, 8:00am–4:30pm) or email [email protected] — we've been supplying trades for over 25 years.
FAQ
What is a penny washer?
A flat washer with a large outside diameter relative to its hole size, used to spread load over soft materials or cover oversized holes. Also called a repair washer or fender washer.
What sizes do penny washers come in?
Our range covers M5 to M12 hole sizes with outside diameters from 20mm to 50mm, in zinc plated and A2 stainless steel.
Are penny washers and repair washers the same thing?
Functionally, yes — "repair washer" describes the job of covering a damaged or oversized hole, which is a penny washer's signature use.
When should I use a penny washer instead of a normal washer?
On soft base materials, over damaged or oversized holes, or anywhere you need more bearing area under a bolt head or nut.
