Caster & Wheel Terminology
Definitions and Terms

Caster and Wheel Terminology

Autoclave / “Autoclavable”:
Sterilizing equipment uses either pressure & steam at 250Åã F to 280Åã F for 10 to 20 minutes, or dry heat up to 375Åã F up to 3 hours. Autoclavable wheels can withstand heat and steam environment.

Axle: Bolt that attaches wheel into caster yoke (frame, bracket).

Bearing Cap: Part used with single precision bearing wheels; integrates a spanner thrust bushing with bearing guard, only covers the bearing and not the full wheel hub. 2 per wheel.

Bearings: Wheel bearings provide either mechanical rolling assistance or a slick surface that reduces friction and increases roll-ability. Raceway bearings are a device on a swivel caster, enabling it to turn while bearing the load.

Blank Wheel: Wheel without bearing installed (plain bore). Bolt Hole Pattern: Measurement between mounting holes on top plate, including length and width dimensions.

Bore: Refers to inner dimension of blank wheel or bearing.

Brake: Component part of caster, when activated, assists in stopping wheel from rolling.

Caster: Complete assembly of caster yoke (frame), wheel(s), & axle; enabling equipment to roll.

Caster Pad: Assembly that is either welded or bolted to the bottom of a piece of equipment that enables a caster with a top plate to be quickly installed or removed. May also refer to a weld plate that has an identical overall size and bolt pattern to casters to reinforce mounting area.

Centered Hub: Wheel hub that has the same dimensions on either side; typically used in casters. Hub usually protrudes from wheel core.

Chemical Bond:
Method of bonding wheel tread to wheel core using glue or a chemical reaction that fuses the materials together.

Cold Forged: A chemical procedure softening steel for forming. Heat treat is usually followed after cold forge to re-enhance the steel strength.

Complete Wheel: A wheel that has bearings installed.

Crown Tread: Wheel face that is slightly rounded; reduces surface area & friction. Crown tread helps wheel roll & turn easier.

Cut & Welded Design: Describes casters made using a raceway & legs that are formed separately & welded together instead of stamping one piece.

Double Ball Raceway:
2 sets of bearings rolling in tracks held together with a kingpin; one set supports the load, while the other assists in swivel thrust.

Drop Forged / Hot Forged: A procedure that billet is heated to burning red before being stamped to certain shapes that otherwise could have been done by welding. The process increases the density of metal & further enhances its strength by eliminating any inconsistency of welding. Most of our heavy duty casters are made with top plate, raceway and king bolts forged to one piece.

Durometer: System of establishing the hardness of rubber, plastic or polyurethane using an “A” scale or "D" scale when it is beyond "A" scale's range.

Dust Cap: Metal cap that helps keep foreign materials out of raceways.

Dynamic Load: Maximum load of a caster/wheel while rolling.

Fastening Type: Refers to the way a caster is attached to a piece of equipment. (i.e.: top plate, stem, hollow kingpin, and etc).

Floor Lock: Accessory used in conjunction with casters; a devise to secure carts from moving on level floors.

High-Temp: Casters or wheels (including all parts), that are capable of operating at higher temperatures without failure or deformation.

Hollow Kingpin Caster:
Tubular rivet used to hold swivel raceways together; the hole in the rivet kingpin can accept a bolt or customized modular stems for any particular mounting requirement.

Hub Length: Distance from one side of wheel hub to the other.

Inner Diameter "I.D.": Measurement of wheel bore, bearing bore or tubing inside diameter.

Integrally Forged: Different components are made into one single component through hot forging process. The process increases the density of metal and further enhances its strength by eliminating the problem of one or more components failure at severe application.

Keyway: Machined notch inside the wheel bore allowing wheel to be locked onto a drive shaft using the “key” that slides into correlating notches between the wheel bore and drive shaft, shaft is then able to turn the wheel. Wheels with thick metal hubs can be machined with keyways.

Kingpin: Bolt or rivet used to hold swivel raceways together; some of our heavier duty drop forged casters have the kingpin integrally forged as one piece with the top plate. Kingpins are typically the weakest point of a caster; Kingpinless casters are stronger.

Kingpinless: Casters without a bolt & nut kingpin. A Kingpinless caster’s top plate and inner raceway are a one piece construction or integrally forged; the outer raceway with legs attached are held together with the inner raceway by hardened steel ball bearings. This design offers unsurpassed durability and use in abusive and demanding shock load applications that may cause kingpin casters to fail.

Load Capacity: Maximum weight carried by a single caster or wheel under ideal operating conditions. Overloading could result in catastrophic failure.

Mechanical Bond:
Method of bonding wheel tread to the wheel core by means of inter-locking materials together.

Modular Stem Casters: Casters created to accept a variety of customized fastening requirements.

Mounting Bolt / Attaching Bolt:
Fastening bolt or screw to attach casters to equipment.

Offset Hub: Wheel hub that protrudes on one side and is recessed on the other; Offset hubs are popular on wheels used on hand trucks and other mobile equipment using wheels instead of casters.

"O.D.": Measurement of the outside diameter of a wheel, bearing, tube, socket, etc.

Plain Bore: Wheel bore that rides directly on axle, no bearing.

Raceway: Section of a swivel caster or wheel bearing; bearings that roll in an embossed or machined track.

Retainer Washer: Washer to keep bearings & grease in & debris out.

Rivet Axle: Permanent axle type used mostly on light duty casters.

Rivet Kingpin: Kingpin that has the both ends enlarged by hydraulic spin or staking, to hold a swivel raceway together.

Seals: Select swivel raceways & wheels may have seals installed to keep debris out and keep grease in. Some wheel bearings are sealed and don’t require maintenance. Check temperature ranges & limitations.

Shock Load: Impact or vibration sustained by caster/wheel from loading or outside forces, such as weight dropped on equipment, equipment running into obstacles.

Side Thrust:
Horizontal force from non-rolling direction of a caster.

Stamped Yoke: Main portion of caster frame assembly made from a single stamped piece of steel instead of multiple parts welded together.

Static Load: Maximum load of a caster/wheel while stationary.

Thread Guards: Metal or plastic disks that cover wheel hub preventing debris from getting into bearings or wrapping around axle.

Thrust Washer: Washers used between wheel hub and caster leg.

Wheel: Wheel only, not in a caster frame.

Yoke: Swivel or rigid frame of a caster. Also referred to as Fork or Rig.

Zerk: Grease fitting on wheels, caster raceways or axles.