RWM Casters, Wheels and Material Handling

Glossary of Caster Terms

Listed and defined below are common terms used to describe and specify casters and wheels. This information is offered for your convenience.

• Brinelling - A permanent deformation of a ball raceway that resembles dimples, caused by the ball bearings during severe loading or severe impact.
• Cold Forging - A process in which extremely heavy presses are used to form the integral parts of a swivel section the top plate, yoke, and bottom. Cold forging not only provides silk smooth raceways, it also improves the strength of the swivel section work hardening the steel to change and yield greater mass resistance at stress points.
• Durometer - Scale for measuring the hardness of a wheel material.
• Hot Forging - A process in which extremely heavy duty presses/hammers are used to shape heated billets of steel. This process allows steel to be formed to various shapes and thicknesses within the same part to aid in handling stress points.
• Kingpin - A rivet or threaded stud or bolt with nut which integrally holds the mounting plate and horn assembly of a swivel caster together. The size and type of the kingpin is one of the most important components in caster selection and loading.
• Kingpinless - A patented swivel section which is held together without a rivet or nut and bolt kingpin. Kingpinless swivel sections are held together by a single row of ball bearings which are contained by a full contact interlocking swivel raceway design.
• Load Capacity - The load a caster wheel will hold.
• Main Load Bearing - The row of steel balls or rollers that swivels the horn base in relation to the mounting plate of a swivel caster and must be properly sized to counteract the direct or radial thrust load.
• Mounting Plate - The flat base (usually with four bolt holes) that forms the top of the caster and permits attachment by bolting or welding to a flat surface.
• Overall Height - The total vertical distance from the floor to the top of the mounting plate, or the base of the stem of the caster.
• Raceway - A channel that consists of one or two rows of ball bearings or rollers, which allows a caster to swivel.
• Radial Thrust - The downward forces exerted on the caster by the load and loading. This force is counteracted by the main load bearing.
• Retaining Washer - A washer pressed into the hub ends to retain the bearings. A sealed version of this washer keeps grease in and debris out of the bearings.
• Rig - A caster without a wheel and axle.
• Rollability - The ease of starting and maintaining rolling motion. Rollability is determined by many factors like, durometer of the wheel, floor conditions and surfaces, load, and size of wheel bearings.
• Side Thrust - Side forces exerted on a swivel caster and properly counteracted by the secondary load bearing.
• Spanner Bushing - A non-rotating sleeve of hardened seamless steel tubing that fits over the axle in roller bearing caster wheels. It serves a dual purpose of providing a smooth inner raceway for the wheel roller bearing and strengthening the caster by permitting the legs to be tightened against it.
• Swivel Lead - The distance between the centerline of the kingpin and the centerline of the axle of a swivel caster. The larger the offset, the easier swiveling, but the smaller offset offers greater strength.
• Swivel Radius - The horizontal distance from the center of the Kingpin to the edge of the tread of the wheel.
• Thrust Washer - A steel washer between the hub ends of the wheel and the inside of the caster legs.
• Tread Width - Width of the wheel tread.
• Wheel Diameter - The distance of the wheel measured vertically from one side of the tread to the other.
• Yoke - The caster part, which comprises legs, plus a base (horn base for swivel caster or mounting plate for rigid).