A Primer on Casters

Moving heavy loads around the workspace manually is a not uncommon task, so it pays to familiarize yourself with the equipment you’ll need to purchase. For most purposes, the working components are the same: namely, casters that are mounted onto carts, trucks or specific equipment. Many people overlook these devices and don’t really think of them as assemblies in themselves. However, as with anything else, a basic understanding helps you make an informed decision on what to purchase and use, whether new or as replacements.

What is a Caster?

A caster is a wheeled device that is mounted to the underside of a larger object to enable easy rolling movement of a load too cumbersome to carry manually. They’re ubiquitous among equipment in many work environments and applications, from automotive factories and heavy industry to office furniture and hospital beds. Many refer to casters as simply “wheels”, but the wheel is only one element of the whole. The bracket that makes up the rest consists of:

  • an outer frame, also called a “yoke” or “fork”, that holds the wheel and its axle in place;
  • a spring mechanism for shock absorption, which can be a coiled steel spring or a hydraulic or elastomeric spring;
  • a mounting mechanism at the top, either a plate bolted to the underside of the equipment or a stem that is screwed or otherwise fastened into place;
  • optionally, a swivel head for 360° movement in “swivel” casters—those lacking this are instead “rigid” or “fixed” casters.

Considering Caster Designs

All casters have the same basic functionality, but many aspects of the design vary based on the intended application. This includes the cart or equipment the casters will be mounted on, the expected weight and dimensions of the load being supported, the type of floor the casters are rolling on and the environmental conditions the casters will be exposed to. For instance, in a machine shop or assembly line, high load tolerance is often vital, as is chemical resistance; a hard rubber wheel featuring stainless steel roller bearings is hardy enough for the job. If you’re replacing casters for a hospital bed, ease of movement, shock absorption and minimal noise are important for patient comfort. A low profile and higher swivel resistance allow better handling, especially across multiple floor types. These are just a few examples, but they highlight how the design of a caster is dependent on how and where it’s going to be used.

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