What Is A Caster?

A caster is a complete wheel and horn assembly which, when attached to a piece of equipment, provides mobility for that product. Swivel casters have a swivel horn and wheel assembly that will rotate 360°. Rigid casters have a rigid horn and wheel assembly permitting only straight line travel.

Caster Parts & Nomenclature

Top Plate — A horizontal plate for attaching a caster to equipment.

King Pin (staked king pin or nut & bolt assembly) — A threaded nut & bolt or staked assembly which holds the swivel assembly together. The king pin may also be an integral part of the top plate. Threaded king pins can be adjusted to compensate for wear in the swivel assembly.

Swivel Horn Assembly — Consists of a swivel bearing unit, an axle and a nut. It does not include wheel, wheel bearings, washers, or spanner bushing components. The spanner bushing is a non-rotating sleeve of seamless steel that fits over the axle and provides an inner raceway for wheel bearings. It strengthens the caster by allowing the legs to be tightened against it.

Rigid Horn Assembly — Consists of a rigid or stationary horn unit, axle and nut. It does not include the wheel, wheel bearings,
or spanner bushing.

Swivel Bearings — Swivel horn assemblies may be supplied with several styles of swivel bearings. For example:

 

1. Single Level Ball Race — A single row of balls in a large
diameter ball raceway.

2. Bi-level Ball Race — A single row of balls moving through
two levels of ball races.

3. Double Ball Race — Two rows of balls moving independently
through two levels of ball races.

4. Ball Bearing Upper Race and Tapered Roller Thrust — A single
row of balls in the upper race coupled with a precision tapered
roller bearing in the lower race.

5. Precision Upper Race and Lower Race Bearings — A self-contained precision load bearing for the upper race coupled with a precision
tapered roller bearing in the lower race.