Glossary of Caster Terminology.

Glossary of Caster Terminology


The bearing that is in the wheel center riding on the axle.  Bearings vary from plain bore (no bearing) to precision ball bearings, with many alternatives affecting cost, ease-of-roll, initial roll-force, noise level and overall performance.

Bearing Covers

Round, plastic covers placed on either side of the caster wheel, covering the end of the bearing. Initially used to keep thread from winding on the axle or in the bearing in textile factories.  Also used for appearance and cleanliness.

Bore Size

The inside diameter of the bore of the caster wheel. The axle can be no larger than this. Varies based on the size of wheel and type of bearing.


Pedal Total Lock: This brake is located above and in front of the wheel(s), locking both the swivel and the wheel.

Pedal Style, Wheel Lock: This brake is located above and in front of the wheel(s), locking only the wheel.

Pedal Style, Swivel Lock: This brake is located above and in front of the wheel(s), locking only the swivel.

Top Lock Brake: This brake is located alongside the caster, mounted on the axle, locking only the wheel by means of pushing a metal brake down against the top of the wheel.

Cam Style: This brake is located alongside the caster, mounted on the axle, locking only the wheel by means of squeezing the sides of the rig against the wheel.

Thumb Screw: This brake is set screw which, when tightened, is applied against the side of the wheel.

Spring Pin: Similar to a thumb-screw brake, a sliding device engages a pin into small cavities in the side of the wheel.


By definition, a caster is "...a wheel or set of wheels mounted in a swivel frame." (Merriam Webster).  So asking for a swivel caster is technically redundant and asking for a rigid caster an oxymoron.

From a practical (and customer service) standpoint, casters are an assembly of a rig, connector and one or more wheels designed for attachment to a larger item to allow that item to be more easily handled.

For lightweight applications, installing all swivel casters usually works well and provides the user ultimate mobility and flexibility. For applications with more than a few hundred pounds of weight, having two rigid (non-swivel) caster will significantly help the user control the cart. For the best of both worlds, look for casters that have direction-locks or position locks which, when engaged, disallow the swivel from moving and force the caster to act as a rigid.


That's the other one - the castor with an 'O' which is the common spelling in Europe. Additionally, it can be defined as: 1) The more northern of the two bright stars in the constellation Gemini; 2) a substance consisting of the dried perineal glands of the beaver and their secretion used especially by perfumers; and 3) a beaver hat. Seriously.  

So, be careful with the spelling on your purchase orders or you may end up with a crate of beaver hats. Please excuse the lead time.

Caster Oil

Should help your caster run faster.

Castor Oil

May make you run faster.

Change Plate

A plate which is bolted or welded to the customer's application, which can hold a caster by means of a snap plate or single bolt. They make replacement of the caster quicker and easier.  These are used in environments when the casters are frequently damaged and replaced, saving repair and maintenance labor.


The method of connecting the caster to the application. Most common connectors are top plates (which screw, bolt or weld to the application), grip rings, grip necks, threaded stems, round stems or specialty connectors.


A classification of casters which provide the easiest initial roll in the attempt to reduce the effort or strain on the user. They typically include high-quality bearings and specific wheel materials.


This refers to the finish or color of the rig (in the case of single- or dual-wheel casters) or the wheel or hood (in the case of twin-wheel, spherical or ball casters).

Floor Lock

Floor locks, sometimes referred to as Truck Locks, act as brakes for carts. Often intalled in pairs on opposite side of a cart, the floor lock is intended to make firm contact with the floor when engaged. They are not meant to lift the cart - most of the weight should remain on the casters or wheels. The floor lock, when extended or engaged, should be 1/8" to 1/4" taller than the load height of the caster to operate properly.

Hub Length

The length of the bore of the caster wheel.  The axle must be at least this long to carry the wheel and fasten to the rig.

Institutional Casters

Casters specially designed to provide quiet, easy-rolling performance in hospitals, retirement facilities, motels, hotels, convention centers, museums, libraries and similar venues. The wheels are typically soft, non-marking materials such as TPR, polyu on polyo, or non-marking rubber. These casters can be plain bore (no bearing) or delrin/ nylon spanner but more often have ball bearings or precision bearings for easy and quiet use.

Leveling Caster

These casters have a threaded adjustment pad behind the caster allowing for slight adjustments to the overall height.

Load Capacity

The amount of weight that each unit is rated to bear. This amount fluctuates most based on wheel material and wheel width.

Load Height

See Overall Height


This refers to the wheel material to be used.


A classification of wheel materials that will not leave marks on the floor. Especially important in office, institutional and some factory setttings.


Options for casters are any extra features beyond the rig, wheel and bearing. They include brakes, position locks, thread guards, specific colors or finishes, hoods (on twin-wheel casters) and others.

Overall Height (OAH)

Also referred to as Load Height, this is the distance from the floor to the bottom side of the application after proper installation of the casters. Measured to the top of the top plate, shoulder of the grip ring or grip neck and top of the swivel raceway for a hollow kingpin or threaded stem caster.

Position Lock

A lock which prevents the swivel from rotating, allowing an item to be easily pushed in a straight direction. Very helpful for items which are parked in a small space.


This is the serious of bearings comprising the swivel of the caster. Raceways may be single, double or kingpinless.

Rig (Yoke)

The body of the caster that holds the wheel in place by means of the axle holes. The rig will have the connector built into or attached to it. Rigs may be purchased separately for replacement. This term applies to single- and dual-wheel casters and not to twin-wheel, spherical or ball casters.


The level of ease of rolling the application. This is most impacted by the wheel diameter and the bearing.

Shock Absorbing Caster

A classification of casters that have a integrated spring so that shock are absorbed rather than potentially damaging to the caster components.

Shock Load

The occurrence of a sudden force against the casters. May be brought about, for instance, by rolling quickly over a significant obstacle or dumping weight suddenly on the application. Certain bearings and wheel materials are better than others at absorbing and tolerating shock loads.

Swivel Radius

The distance from the center point of the swiveling connector to the furthest edge of the wheel.

Thread Guards

Round, metal plates placed on either side of the caster wheel, covering the end of the bearing. Initially devised to prevent thread from winding on the axle or in the bearing in textile factories. Also used for appearance and cleanliness.

Wheel Diameter

The height of the wheel as it stands in it's rolling position..  The larger the diameter, the easier the roll.

Wheel Width

The width of the wheel as it stands it's rolling position. Wider wheels generally provide higher weight capacity.


See Rig

Zerk Axle

An axle with a grease zerk on the end and a channel which delivers grease to the inner wheel bearing.

Quick Email!

Have questions about our products? Wondering what caster would best suit your needs? Just saying hi? Drop us a line here!

This value is required.
This value is required.
This value must be a valid Email Address.
This value is required.