Cup Washers

Cup Washers

Cup washers (penny washers or repair washers) provide an oversized bearing surface under bolt heads and screw heads — distributing clamping load over a larger area and preventing pull-through in soft materials and oversized or damaged holes. AIMS Industrial stocks cup washers in zinc-plated steel and stainless steel across a range of bolt and screw sizes for construction, maintenance and repair applications.

When Cup Washers Are Used

Cup washers are specified in timber and lightweight panel construction where standard flat washers would pull through under load — roofing and cladding fixings where oversize holes are common, repairs to fixing points where the original hole has wallowed out, saddle and strap connections in timber framing, and garden structures, fencing and playground equipment where weather exposure demands a large bearing surface at every fixing point to prevent localised crushing and water pooling around bolt heads.

Difference Between Cup, Flat and Structural Washers

A standard flat washer provides moderate bearing area increase — suited to general bolt and nut use in metal and dense materials. A cup washer provides a substantially larger bearing area — suited to softer materials and over-size holes. A structural (F436 or similar) washer is a precision-hardened flat washer for structural bolt connections with defined load-bearing properties. For most timber and sheet material repair and fixing applications, a cup washer is the appropriate choice.

Sizes and Materials

Cup washers are sized by the bolt/screw diameter they suit — M4, M5, M6, M8, M10 and M12 being the most common. Outer diameters typically range from 20mm to 50mm depending on the nominal bolt size and the amount of bearing area increase required. For help selecting the right washer type and size for your fixing application, contact our team. AIMS Industrial has been supporting Australian tradespeople since 1988.