Bearing: A mechanical device that allows the moving parts in a caster to move more easily. Usually either a roller bearing, a ball bearing, or a delrin bearing.
Bore: The hole through either the middle of a wheel or the bearing in the middle of the wheel.
Brake: A device on a caster that keeps the wheel from rolling.
Durometer: A measure of the hardness of resilient tread wheels.
Dynamic Load: The load or weight on a caster when it is moving.
Fork Assembly: The caster assembly less the wheel and axle. It is the metal part of a caster immediately attached to a piece of equipment. Also called ‘rig’ or ‘horn’.
King Pin: The nut & bolt or rivet that holds the swivel bearing assembly together.
Load Capacity: The maximum load per caster or wheel recommended for intermittent operation over smooth floors at speeds of 3 mph or less.
Load Height: The vertical distance between the floor and the bottom surface of the apparatus to which the caster is attached.
Raceway: The surface on which bearing rollers or balls move.
Rigid Caster: A rigid caster has a fork that remains stationary relative to the bottom of the equipment on which it is attached. Rigid casters are also called ‘stationary’ or ‘fixed’.
Spanner Bushing: The fixed sleeve or bushing through which the axle runs and on which the wheel bearing turns.
Swivel Caster: A caster with a swivel fork that permits it to rotate 360 degrees relative to the bottom of the equipment upon which it is attached.
Swivel Lock: A device on a caster that prevents the swivel assembly from turning.
Swivel Raceway: One or two rows of ball bearings in the raceway that allows the caster to swivel more easily than it would otherwise.
Thread Guard: A small disk of plastic or metal that fits over the axle between the wheel and the inside of the fork, used to prevent dirt or other materials from getting into the wheel bearing.
Total Lock: A device that simultaneously prevents a caster from both swiveling and rolling.