Caster terminology

1. Measuring terminology

  • Size of caster is often based on mm or inch (1 inch = 1" = 25.4mm = 2.54 cm)
  • 1. Wheel diameter: The distance of the wheel measured vertically from one side of the tread to the other. The larger the diameter the more load capacity and much easier the caster can roll on floor and over obstacles. Popular sizes are: 1" = 25mm, 2" = 50mm, 3" = 75mm, 4" = 100mm, 5" = 125mm, 6" = 150mm, 8" = 200mm, 10" = 250mm, 12" = 300mm
  • 2. Load height: The total vertical distance from the floor to the top of the mounting plate or the base of the stem of the caster
  • 3. Bolt hole spacing
  • 4. Swivel radius: The horizontal distance from the center of the kingpin to the edge of the tread of the wheel
  • 5. Wheel width: Width of the wheel tread
  • 6. Shaft diameter/ Ball bearing's inner diameter: For bushing/ bearing wheels accordingly
  • Others: wheel hardness durometer scale, wheel hardness, thickness of steel bracket, diameter of bearing ball in the raceway, etc.

2. Describing terminology

Bushing wheelBearing wheelSwivelRigid
Swivel with side brakeSwivel with dual brakeScrewScrew with side brake
Screw with dual brakeStemStem with side brakeStem with dual brake

Installing types:

    • a. Top plate type: A square or rectangle steel plate is on top of the caster. It often has 4 - 6 holes to secure bolts and nuts with the cart's plate.
    • b. Screw type: On top is a M8, M10, M12, M16, etc. threaded stem. It is used to connect with the cart's tube legs. Preferable for light and medium duty only.
    • c. Stem type: A solid stem or a long tube. Usual seen in scaffold.
    • d. Others: Modular type, Splinting stem type, etc.

Caster type: Swivel, Rigid, Swivel with brake. Brake can be single (lock only the rolling of the wheel) or dual brake (lock both wheel's rolling and caster's rotation).

Note: Please be noted that currently the Rigid type has no brake and no Screw type in Vietnam's caster market.

Bearing types: Bushing (Sleeve) and Bearing

      • a. Bushing: Metal sleeve is inserted in wheel and rests directly on axle. Only recommended when rolling ease is less critical.
      • b. Bearing Recommended for maximum rolling ease with no maintenance lubrication required. Quiet operation for medium duty to heavy duty loads. Includes ball bearing and roller bearing.

3. Wheel's parts terminology

3.1. Wheel with ball bearing

3.2. Wheel with roller bearing

Roller bearing wheel

1: Ball bearing

2: Wheel

3: Bushing

Ball bearing wheel

1: Washer

2: Wheel

3: Roller bearing

4: Roller

5: Bushing

4. Caster's part terminology

4.1. MEDIUM DUTY CASTER ANATOMY

  • 1. King Bolt & 2. Rivet (Kingpin): Holds the mounting plate and yoke assembly for a swivel caster together
  • 3. Mounting Bolt Holes: Where the bolts attach the caster to the cart
  • 4. Top Plate: The plate which attaches the caster to the application
  • 5. Load Race: Row of steel balls or rollers that allow the yoke base to swivel
  • 6. Load Ball Bearings: One or two row of steel balls or rollers
  • 7. Yoke Base: Flat part of the yoke which the legs attach to
  • 8. Zerk Fitting: Fitting that is provided for injecting grease into the caster
  • 9. Thrust Race: Holds the thrust bearings in the yoke base
  • 10. Legs: Supports the axels
  • 11. Axle Hole: Holes that hold the axles
  • 12. Thrust Ball Bearings
  • 13. Button: Forms the lower raceway of the Thrust Race
  • 14. Kingpin Nut: Holds the swivel section together

4.2. HEAVY DUTY CASTER ANATOMY

  • 1. Mounting Plate and Kingpin: A flat plate with an Integral Kingpin
  • 2. Load Bearing (Commercial): Row of steel balls or rollers that allow the yoke base to swivel
  • 3. Yoke Assembly: The yoke base with legs welded on and machined for the Main Load Bearings
  • 4. Axle Bolt: The bolt on which the wheel revolves
  • 5. Axle Bolt Nut: Secures the axle bolt to the yoke assembly to form the axle
  • 6. Thrust Bearing: The row of bearings that operate between the yoke base and the retaining washer
  • 7. Retaining Washer: Keeps the bearings retained
  • 8. Kingpin Nut: Holds the swivel section together
  • 9. Spanner Bushing: A tube that spans between the legs, over the axle, on which the roller bearing rides