How to Know When you Need a Shim or Washer

Washers and Shims, what are they, and why do we need them? A shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects.

A washer is a thin plate (typically disk-shaped) with a hole (typically in the middle) that is normally used to distribute the load of a threaded fastener, such as a screw or nut.

Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear.

Many materials make suitable shim stock, or base material, depending on the context: wood, stone, plastic, metal, or even paper (e.g., when used under a table leg to level the table surface).

High quality shim stock can be bought commercially, for example as laminated shims, but shims are often created ad hoc from whatever material is immediately available.

Washers are usually metal or plastic. High quality bolted joints require hardened steel washers to prevent the loss of pre-load due to Brinelling after the torque is applied.

Rubber or fiber gaskets used in taps (or faucets, or valves) to stop the flow of water are sometimes referred to colloquially as washers; but, while they may look similar, washers and gaskets are usually designed for different functions and made differently.

Other uses are as a spacer, spring (belleville washer, wave washer), wear pad, preload indicating device, locking device, and to reduce vibration (rubber washer). Washers usually have an outer diameter (OD) about twice the width of their inner diameter

Laminated shim stock is stacked foil that can be peeled off one layer at a time to adjust the thickness of the shim.

In manufacturing, shims are commonly used to adjust the clearance or space between two parts. For example, shims are inserted into or under bucket tappets to control valve clearances. Clearance is adjusted by changing the thickness of the shim.

Washers can be categorised into three types;

‘plain washers’, which spread a load, and prevent damage to the surface being fixed, or provide some sort of insulation such as electrical; ‘spring washers’, which have axial flexibility and are used to prevent fastening loosening due to vibrations; and ‘locking washers’ which prevent fastening loosening by preventing unscrewing rotation of the fastening device; locking washers are usually also spring washers.

The term washer is also often used for disc shaped devices used as grommets.

Phoenix Specialty manufactures precision Washers and Shims.  Washers and Shims are manufactured to your specifications.

For over 100 years, we have been the leading supplier of custom specialty Washers and Shims to Original Equipment Manufacturers (OEMs).
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