What is a Caster?

Purchasing Shepherd Casters in Bulk: The Quick-Step Buying GuideWe all know what a caster is, right? It’s that wheel on the bottom of the office chair you might just be sitting on. End of article!

Then again, there are as many types of casters as there are fish in the sea—or, perhaps, species of fish in the sea. So, prepare to be educated on the wonderful world of casters!

So, Just What Is a Caster?

In short, a caster is a wheeled device that is mounted to a larger object that enables the larger object to be moved about easily. You’ll find casters everywhere, from household furniture to portable pieces of equipment in large production environments. Casters can be very small, and they can be extremely large, with weight-bearing capacities ranging from 100 lbs. all the way up to the thousands.

What Makes up a Caster?

A caster is made up of several parts:

·        The Mount

The mount is the part of the caster that is used to affix it to the item it is designed to transport. There are two main types of mounts – a top plate or a stem. A top plate is a small metal plate that’s usually square and is drilled with holes, typically one hole in each corner. The plate is then screwed to the item. A stem is a bolt or screw that is fitted into a large single hole that is drilled into the item.

One alternative mount is a snap mount. This is a socket that the caster is snapped into. Usually snap mounts are used only for temporary or occasional caster use.

·        The Yoke

The function of the yoke is to provide a frame for the wheel. The yoke (or frame, fork, housing, or rig) is the part of the caster that is attached to the top plate by screws or welding. Some casters are molded so that the yoke and top plate are formed out of the same piece of material.

·        The Swivel Plate

The swivel plate is only used on swivel casters and not on rigid casters. Rigid casters are fixed in place, whereas swivel casters can rotate 360 degrees. The swivel plate is fixed to the mount, and also fixed to the yoke. The swivel mechanism is likely to contain bearings and grease in order for the caster to retain its swiveling capabilities for the entirety of its lifetime.

Some swivel plates have openings where grease can be administered if the caster begins to stick. These are known sometimes as zerks.

·        The Spring

Casters are frequently used on items where comfort is important, like furniture. In many cases, these casters are fitted with shock absorption features and in particular springs. The usual spring mechanism is a single coiled steel spring. A spring will cushion the caster when a load is placed upon it. Other shock absorption features can include hydraulics, and elastomeric springs (polymer with similar properties as rubber).

·        The Wheel

You cannot have motion without a wheel. Therefore, you cannot have a caster without motion! The two main types of wheels are solid and bonded. A solid wheel is made out of one single material, whereas a bonded wheel has a solid core and tread which is made from a different material. The tread is then bonded to the core.

There are many different materials used to make caster wheels – rubber, polyurethane, phenolic, nylon and metals such as iron, aluminum and steel. The type of wheel (and subsequently, the type of caster) that’s best for a specific application is dependent on a number of factors, such as load dimensions, ease of roll required, condition of flooring, and type of environment.

·        The Wheel Bearings

Wheel bearings are typically small metal balls that are positioned around the wheel and are held in place by a metallic ring that’s known as a race. The wheel of some casters does not rotate around a central axle, but instead the ball bearings allow the outer part of the wheel to rotate around the central wheel hub.

The use of ball bearings allows for easier motion, and most ball bearings used in casters are made from steel, but other materials are also used. It’s important that ball bearing assemblies are kept lubricated in order to prolong the caster’s usefulness.

·        The Axle Bolt

The axle bolt simply affixes the wheel to the yoke. Sometimes a nut is used to fix the bolt, or the axle is molded to the yoke.

Are There any Optional Caster Components?

Casters may also come with brakes and guards.

The Brake

If an item of caster-mounted machinery or equipment needs to be secured in one place, then a caster can be fitted with a brake in order to prevent unwanted movement. These are usually simple devices that are fitted into the yoke. Most are operated by foot. Pressure is applied to the top of the brake, and the brake itself is applied to the edge of the wheel’s tread to prevent it from moving. Some other types of caster have brakes that squeeze against the side of the wheel in the same manner that disk brakes work in automobiles.

The Guard

When working in debris-strewn environments, there’s always the chance that debris will find its ways within the important internal components of the caster, including the wheel bearings. This significantly decreases the lifespan of the caster, and prevents smooth operation. A caster can be mounted with guards that protect the wheel from such contamination. There are several types of guards, but all perform a protective role.

Congratulations, You are Now a Caster Expert

Now that you know all about casters, you’re ready to speak to the true experts – the sales support team at Douglas Equipment. We can help you with all your caster needs from advice to after-sales support.

To contact us, all you have to do is call 1-800-451-0030, or use the online form to reach out to us today!