Caster Glossary: 50+ Terms Every Buyer Should Know

The bolt or pin that the wheel rotates around. The axle passes through the wheel hub and is supported by the wheel bearings. Most industrial casters use a precision-ground axle bolt secured with a locking nut.

The fastener that serves as the axle, passing through the wheel hub bearings. Should be specified as a matching grade to the caster's load rating, using an undersized axle bolt with a heavy-duty rig compromises load capacity.

A rolling element bearing using spherical steel balls to reduce friction between the axle and hub (wheel bearing) or between the swivel plate and rig (swivel bearing). Precision ball bearings are the lowest-friction, longest-life option for most industrial and commercial caster applications.

A full circular ring of ball bearings used in kingpinless swivel designs. See Kingpinless Caster / Raceway Swivel for full details.

The diameter of the hole in the wheel hub through which the axle passes. Common bore sizes: 1/2", 5/8", 3/4", 1". Must be matched to the axle diameter.

A mechanism that restricts the movement of the caster wheel, swivel, or both. See also Total Lock, Swivel Lock, and Wheel Brake for specific brake types.

The force required to initiate movement from rest. For swivel casters, swivel breakaway force is the torque required to start the swivel rotating from a stopped position. Relevant in ergonomic assessments.

The maximum weight a caster is rated to support. Always expressed as weight per caster, not per set. Load ratings assume static conditions; dynamic, impact, and asymmetric loads require a safety factor. See Safety Factor.

A wheeled device that attaches to a cart, equipment, or furniture to enable mobility. Consists of a wheel, bearings, axle, and a mounting mechanism (plate or stem). A swivel caster adds a rotating swivel rig.

The total vertical distance from the bottom of the wheel to the top of the mounting plate. Important for matching replacement casters and for AGV/automated applications requiring precise deck height.

A surface treatment applying a thin layer of chromium to steel components. Provides moderate corrosion resistance and a bright appearance. Not appropriate for washdown environments, see Stainless Steel Casters.

A caster designed to provide a low-resistance path to electrical ground, dissipating static electricity. Resistance: less than 1,000 ohms. Required in some electronics manufacturing and explosive environments.

A wheel with a hollow center section between the tread and the hub. Reduces weight while maintaining load capacity. Common in phenolic and nylon wheels.

A permanent flat area on the wheel's rolling surface caused by prolonged static loading. Most common in rubber and soft polyurethane wheels. Prevents smooth rolling and causes jarring. Prevented by parking loaded carts on rubber mats or specifying harder wheel compounds.

See Swivel Lock. A brake that locks the swivel head from rotating while allowing the wheel to continue rolling.

A caster with two wheels mounted on a shared axle, running side by side. Increases stability and reduces floor pressure by distributing load over a wider tread surface. Common in office chair casters.

A measure of material hardness. Casters use Shore A (for softer materials like polyurethane and rubber) or Shore D (for harder materials like nylon). Lower numbers = softer; higher numbers = harder. Common polyurethane casters are 70A-95A. Common nylon: 65D-75D.

A caster specification providing controlled static discharge. Resistance between 1M ohm and 1G ohm, controlled dissipation rather than direct grounding. Used in electronics assembly, semiconductor manufacturing, and explosive atmosphere environments. Distinct from Conductive Caster.

A stem-type adapter that expands inside a round tube leg when tightened, allowing a grip ring caster to be installed in a tube with a non-standard inside diameter.

See Rigid Caster. A caster with no swivel mechanism, the wheel is fixed in one direction of travel only.

A pneumatic-style caster wheel with foam filling instead of air. Provides cushioning similar to pneumatic without the risk of going flat. No maintenance required. See Pneumatic Caster.

The U-shaped bracket that holds the wheel axle. The fork's width (the space between the two fork arms) determines wheel width compatibility. Also called the leg of the caster.

The most common office chair caster stem type. A spring-steel ring near the base of the stem compresses to insert into the socket and expands to lock in place. Removal by pulling straight out with firm force. Standard sizes: 7/16" x 7/8" or 5/16" x 7/8" diameter x length.

A stem retention design common in European chair casters, similar in function to grip ring but with a different retention mechanism shape.

The center section of the wheel that contains the bearing bore. The hub connects to the axle and transmits load from the wheel to the axle and rig.

The central vertical bolt that connects the swivel yoke to the top plate in a standard swivel caster design. The kingpin is the primary load-bearing and swivel element in conventional swivel rigs. Subject to loosening under heavy use, see Kingpinless Caster for alternative.

A swivel caster design that replaces the single kingpin with a full circular ball-bearing raceway. Load is distributed evenly around the raceway rather than concentrated on a single bolt. Significantly longer service life under heavy loads and high-cycle conditions. Standard for industrial applications above 800 lbs per caster.

See Fork (Yoke). The U-shaped bracket that holds the wheel axle.

See Capacity (Load Rating). The maximum weight a caster is rated to support, always expressed per caster.

A caster with a brake mechanism. Types: Wheel Brake, Swivel Lock, Total Lock. See individual entries for specific locking mechanisms.

The flat metal plate at the top of a plate mount caster. Contains bolt holes for attachment to the equipment frame. Standard hole patterns allow interchangeability between manufacturers.

The arrangement of bolt holes on the top plate. Described by adjacent hole spacing (e.g., 2-3/8" x 3-5/8") or diagonal hole spacing. Must match the equipment's existing hole pattern for direct replacement.

A wheel compound designation indicating the wheel will not leave visible marks, scuffs, or stains on the floor surface. Polyurethane and most rubber compounds are non-marking. Nylon, phenolic, and steel may mark finished floors.

Certification indicating a caster meets the National Sanitation Foundation's standard for food equipment. Required for casters on food contact equipment in commercial and industrial food environments.

See Caster Height. The total vertical distance from the bottom of the wheel to the top of the mounting plate.

A caster wheel made from layers of canvas or cotton impregnated with phenolic resin and compressed under heat and pressure. Very hard, high load capacity (up to 1,400 lbs), temperature resistant to 250°F. Can mark floors. Common in heavy industrial applications.

A caster that attaches to equipment via a flat top plate with bolt holes. The most common mounting type for industrial and commercial carts and equipment. Higher load capacity than stem mount.

A caster with an air-filled (inflated) tire, similar in principle to a bicycle tire. Excellent shock absorption and performance on rough or outdoor surfaces. Requires periodic inflation. See also Flat-Free.

The most common industrial caster wheel material. Elastomeric compound available in a range of hardnesses (70A-95A). Non-marking, floor-friendly, quiet, good load capacity. Preferred for most general commercial and industrial applications.

See Kingpinless Caster. A swivel caster using a full circular ball-bearing raceway instead of a single kingpin.

A caster with no swivel mechanism, the wheel is fixed in one direction of travel only. Provides excellent straight-line tracking and directional stability. Always paired with swivel casters for practical cart use.

The force required to maintain a caster in rolling motion. Expressed in lbs or N. Affected by wheel material, diameter, bearing quality, floor condition, and load. Lower rolling resistance = less operator push force required.

A multiplier applied to the calculated load per caster to account for dynamic, impact, and asymmetric loading conditions. Recommended minimum: 1.25x for smooth-floor applications. Use 1.5x for moderate impact or floor variation; 2.0x for heavy impact loading.

A ball bearing with a rubber or metal shield that prevents contamination entry and retains lubricant. Preferred over open bearings for longevity in industrial and commercial environments.

Hardness measurement scales used for caster wheel materials. Shore A measures softer materials (rubber, polyurethane); Shore D measures harder materials (nylon, rigid plastics). Higher number = harder. See Durometer.

A caster that attaches to equipment via a post (stem) that inserts into a socket in the equipment leg or base. Types: Grip Ring, Threaded, Expanding Adapter. Common on furniture, light equipment, and office chairs.

A caster with the swivel rig, top plate, and hardware manufactured from stainless steel (304 or 316) for corrosion resistance in wet, chemical, or food-grade environments.

A caster with a rotating swivel head that allows the wheel to turn 360°, enabling the cart to move in any direction without lifting.

The horizontal distance from the center of the swivel axis (kingpin or raceway) to the center of the wheel contact point on the floor. Swivel lead causes the wheel to trail and self-align in the direction of travel. Critical specification for towline and AGV cart applications.

A brake that locks the swivel head from rotating while allowing the wheel to continue rolling. Converts a swivel caster to a rigid caster on demand. Used to improve straight-line tracking without permanently installing rigid casters.

The rotating assembly at the top of a swivel caster, including the top plate, swivel bearing (or raceway), and yoke. The swivel rig allows the 360° rotation of the wheel.

A caster stem with external threads that screw into a threaded insert in the equipment leg. Common on European and heavy-duty furniture applications. Must match thread size (M10, M12, 5/16"-18, 3/8"-16, etc.).

See Mounting Plate. The flat metal plate at the top of a plate mount caster containing bolt holes for attachment.

A brake mechanism that simultaneously locks both the wheel (from rolling) and the swivel head (from rotating) with a single action. The strongest locking configuration, the cart cannot move in any direction. Standard for medical equipment, workstations, and any application requiring complete immobility.

The width of the wheel's contact surface with the floor. Wider tread = more floor contact area = more load distribution = less floor pressure.

See Bore. The diameter of the hole in the wheel hub through which the axle passes.

A brake mechanism that locks the wheel from rolling without affecting the swivel head's rotation. The cart can still pivot (swivel) while the wheel is locked. Less complete than Total Lock.

The measurement across the full wheel from tread surface to tread surface. Larger diameter = lower rolling resistance, better obstacle clearance. Common industrial sizes: 3", 4", 5", 6", 8".

The measurement of the wheel tread from side to side. Wider wheels distribute load over more surface area.

See Fork. The U-shaped bracket that holds the wheel axle.

A surface treatment on steel caster components providing moderate corrosion resistance in dry and lightly exposed environments. Not appropriate for washdown, food service, or high-humidity applications. See Stainless Steel Casters for wet environments.