A caster is usually measured by the size of its wheel. For example, a 4" caster would have a 4" wheel -- even though the total overall height of the unit is more than 4" tall. Don't ask us why they do this. We didn't invent the things, we just make them.
Casters come in two basic types: Swivel and rigid. (Some people also call the rigid "fixed" or "stationary" -- which is not a good term for something that is supposed to move. And to add confusion to clarity, a rigid caster is technically an oxymoron since the very definition of a caster is something that swivels!)
Casters
are mounted using fastenings -- usually a plate that
is bolted or welded in place, or a stem that is inserted into
tubing. Fastenings are important because the caster
must be securely fastened to operate correctly.
| Axle. |
| The bolt that runs through the wheel and through the swivel (a.k.a. "kingpin."). |
| Bearing. |
| A bearing is the moving part that allows the caster to move. It refers to both the swivel bearing (a.k.a. raceway), and wheel bearing. |
| Bolt
Holes. |
| The holes in the top plate allowing the caster to be mounted on the cart. |
| Bore. |
| The hole through the middle of a wheel. Also a very tedious person. |
| Brake. |
| Just like the emergency brake on a car -- when applied, it helps prevent the wheel from rolling. |
| Capacity. |
| Also known as load capacity -- the weight the caster will safely hold. |
| Caster. |
| A wheel on a swivel, attached under a piece of furniture or other heavy object to make it easier to move. (The dictionary came up with this definition, not us.) |
| Diameter. |
| The wheel diameter of a caster. |
| Fastening. |
| The method of mounting a caster to the furniture or cart (i.e., top plate, threaded stem, etc.). |
| Hub. |
| The center core of a wheel. |
| Hub
Length. |
| The length of the bore of a wheel. The hub length is usually wider than the tread. |
| Kingpin. |
| The axle that holds the fastening to the caster body and allows the unit to swivel. |
| Load
Capacity. |
| Also known as capacity -- the weight the caster will safely hold. |
| Overall
Height. |
| The total vertical height of the caster, from the floor to the top of the mounting plate, or the base of the stem. |
| Rigid. |
| A caster that doesn't swivel, but still rolls forward and back. Also known as a "fixed" or "stationary" caster. |
| Stem. |
| A fastening that
usually fits into tubing for the caster to be mounted.
Could be threaded, grip ring, round, square, octagon,
or something similar. |
| Swivel
Lock. |
| Just like it sounds: It locks the swivel, making the caster act as a rigid. |
| Swivel
Raceway. |
| One or two rows of ball bearings which bear the weight of the caster and allow the unit to swivel. |
| Swivel
Radius. |
| The horizontal distance from the center of the kingpin to the trailing edge of the wheel. This determines the "sweep" of a caster as it pivots -- a good thing to know to make sure the wheel doesn't strike something as it turns. |
| Thread
Guard. |
| A small piece of
metal or plastic that fits over the wheel bearing to help
prevent threads, dirt, and other materials from getting
into the wheel bearing. Note the spelling -- thread
guard, not tread.
Big difference. |
| Tread.
|
| The part of the wheel that rolls on the ground. Not to be confused with "thread". |
| Tread
Width. |
| The width of the wheel tread. |
| Wheel. |
| You're kidding, right? |
|
