Metal assembly, Rig, Harness or Fork, that "yokes", encases or holds the wheel. The wheel is held in place by an axle between two fork legs. There are two basic yoke types; Swivel and Rigid.

Swivel Yoke: Swivel Yokes let the offset fork legs and attached wheel, rotate or swivel 360 degrees, providing freedom of movement in any direction. There are two types of swivel yokes: Stamped, and cut and welded. The Stamped Yoke base is normally used for light to medium duty capacity casters and is made from one piece of light gauge steel, that is cut out then formed into the leg base and includes a portion of the raceway. The cut and welded yoke type is normally for used for medium to heavy-duty casters and are made of a heavier gauge steel. The legs and the lower raceway pieces are cut out, formed, then welded together. Both Swivel yoke types are made up of four basic parts; The Raceway, Fork Leg assembly, kingpin and fastener.
Rigid Yoke: Rigid yokes do not swivel and provide bi-directional movement and stability in movement when used in conjunction with swivel casters. Rigid yokes are typically stronger than a swivel yoke because there are no moving parts, and the legs are straight instead of offset. There are two types of rigid yokes, a stamped yoke and a cut and welded type. The stamped type is literally one piece of steel, that has been cut and formed. The Cut and welded type takes three cut pieces; Two legs and the top plate that are welded together.

Raceway

One or two sets of bearings that roll or "race" between formed pieces of steel or in a heavily embossed track, that enable a caster to swivel. The raceways of most casters are held in place between the fastener and the fork legs by a kingpin. However there is a type of raceway that is designed differently, it is called a "Kingpinless style raceway." The three styles of raceways will be listed hereafter.

Single-ball raceway: Durable has one series of single-ball raceway casters otherwise known as "General-duty" casters (New 11 series, Old 10 series). This raceway design is the least expensive to Manufacture, and is not designed to last for a long term application. It has one set of bearings that rolls in a single track embossed in the bottom of the top plate fastener and a track embossed in the upper portion of the fork leg assembly. Because the top plate is actually the upper raceway, this series is only offered with a top plate type fastener. It is held together by a rivet style Kingpin. These casters don't do well swiveling in applications that may tend to overload the capacity because this can causes the raceway to bind up or cause part of the raceway to bend and dump the bearings out causing a failure. It is also not recommended in applications that have excessive debris, because the raceway bearings are open and debris can bind prevent the raceways from turning. When customer need an inexpensive top plate caster, this is a good Series.
Double-ball raceway: Most casters ranging from the light-duty to medium heavy-duty capacities have this type of raceway design. There are three main pieces that have 4 embossed tracks on them, the two sets of bearings roll in the embossed tracks. There is a upper and lower cap to the raceways. The upper cap is under the fastener and on top of the caster and has a set of bearings between it and the upper embossment of the top of the leg base. The second set of bearings roll between the top of the lower cap and the bottom of the leg base. The upper raceway handles the load of the weight put on the caster. The lower raceway handles the swiveling action and thrust of the caster. Most medium to heavy duty raceways are hardened to increase the capacity, wear and life of the caster. It is an important selling feature to know if a particular series raceways are hardened or not v/s the competition.
Kingpinless style raceway: This style of raceway is the strongest and least likely to fail in use. It has one set of bearings that roll in a machined and hardened raceway between two pieces of steel. The inner raceway and the top plate are one forged piece. The outer raceway has the legs welded to it and has a hole a little bigger than the bearings in the outer raceway. The two pieces of the raceway are put together and the ball bearings are loaded into the raceway through the hole on the outer raceway. A cap is then welded in the loading hole to seal it up. The bearings hold the raceways together. The strength of this design prevents many of the problems or failures that are possible with the other two raceway designs.

Kingpin

The kingpin is the Nut and bolt or rivet that holds the fastener, fork leg assembly and raceways together. Most lighter duty applications have a rivet type kingpin, and heavier applications usually use the stronger, nut and bolt type. On stem type casters, the bottom part of the stem may actually be the kingpin. The kingpin takes more stress than other parts of the caster, because all the weight is centered on it, (due to the offset of the swivel caster leg). If a caster is used in an application were there is extreme shock loading the kingpin could elongate (stretch), weakening the integrity of the raceway, possibly causing bearing loss or brake the kingpin all together. It is recommended that the kingpinless raceway design be used in heavy and extreme-duty applications as that it does not have the same problems associated with kingpin failure.

Fastener

The fastener is the part of the caster that is used to attach the caster to the piece of equipment it is being used on. The strongest and most common fastener is the top plate. Top plates spread the load over a bigger area, proving strength. Top plates are attached by being bolted or welded to a piece of equipment. A top plate can also be inserted into a quick change plate that is already attached to equipment. Other styles of fasteners are generally not as strong, but are used when there is not space for a top plate. Other types of fasteners: Threaded stems, Grip ring stems, Square stems, Octagon stems, Round stems, Any style of stems with cross drilled holes, Expandable Adapter stems, and Adjustable stems. Some stems are made to work in conjunction with sockets that fit into the hole of a pipe or tubing. They could be plastic or metal.

Axle

The axle is a bolt or rivet that holds the wheel in place between the two fork legs. Some Axles have a hole drilled length wise half way through them and have a grease zerk fitting screwed or pressed into the end of the hole that allows lubrication of the wheel bearing without removing the wheel. These type of axles are called "zerk axles". When axles are sold separately, the will come with a matching nut. Most lighter duty caster yokes come with axles provided, medium to heavy duty caster yokes do not come with axles, but must be purchased separately. Most lighter duty axles have a rounded head with a nipple on the underside that fits into a notch in the axle hole of the caster leg. This design is made for ease in assembling casters and does not require the end of the axle to be held while the nut is being tightened. All bigger axles have a hex head on the bolt and must be held with a wrench when the nut is being tightened. Hex head axles are available upon request for some smaller series.

Bearings

Typically encased balls or rollers that fit inside a wheel that increases the ability of the wheel to roll under a load or reduces the effort required to push a cart. Bearings can also be a bushing press fitted into the I.D. of a wheel providing a slick, wear resistant surface that reduces friction for the wheel to turn on the axle. Bearings are made out of different material types; Galvanized steel, Stainless steel, Delrin, Nylon.

Spanner Bushings

A piece of round tubing used to reduce the inner diameter of a wheel bore or bearing to fit a smaller size axle. Bushings are made out of steel, delrin and other hard slick materials. Bushings may also be used as a bearing or to add stability to a caster. Bushings that are not being used as a bearing are usually slightly longer than the hub length of the wheel, therefore when the axle is tightened, it will tighten down on a bushing preventing the hub from being pinched, and impeding the wheel from turning.

Brakes

Brakes are designed to stop the wheel from turning when on a flat surface. Brakes are not designed, nor should it ever be implied that are brakes will completely stop a cart on an incline. There are many different types of brakes. Most brakes engage on the tread of the wheel, like the Top Lock Brake, Pedal Wheel Brake and Face Contact Brake, however some are designed to pinch the forks together against the hub of the wheel to stop it like the Cam-Lock Brake. A Total-Lock brake is designed to stop both the wheel and the swivel action be depressing a single pedal. There is also a Positionlock brake that enables the swivel action of a brake to become rigid every 90 degrees (4 positions). There is also a thumb screw brake that is a bolt screwed through the side of a fork leg that can be tightened by hand against the wheel and stopping it.

Brake Kit

All the parts needed to add brakes to a caster including the special axle.

Floor Lock

A brake type mechanism that attaches the same way a caster does under a cart. It has a pedal and a rubber pad that presses against the floor causing resistance, when activated. Floor locks can be effective brakes, but they are not designed to be a jack or lift equipment. Most floor locks are designed to be used with 2" tread width casters and have the same top plate size and bolt hole pattern.

Thread Guards

A disk that can be put between the hub of the wheel and the inside of the fork legs that helps prevent debris from getting in the bearings or treads form wrapping around the wheel hub, preventing premature failure of the bearings, excessive wear on the wheel tread and possibly complete caster failure. Thread guards must be used only on wheels with bearings or a bushing and will not work on plain bore wheels. Some wheels come with thread guards installed. Thread guards come in steel & plastic and normally take up most of the dished out portion of the wheel hub. They are similar to hub caps accept they don't rotate with the wheel.

Wheel

Blank Wheel: A wheel that normally uses a bearing but does not have one installed.
Complete Wheel: A wheel that has bearings installed and is ready or complete and needs no other parts to be installed in a caster except the axle.

Retainer Washer

Acts as a seal to keep Roller bearings and grease in wheel bores and debris out of bearings. They are available in steel, delrin, plastic and can be flat or flanged. Some even have a neoprene seal on the I.D. for added seal protection.

Thrust Washers

Steel washers that take up the space or "slop" between a wheel hub and the caster fork legs. Excessive room between a wheel hub and fork leg causes a wheel to wobble or flop back and forth. Thrust washers are used to fix the problem.

Caster Pad

Steel assembly that can be welded on bolted on to a piece of equipment like a garbage dumpster, that you can clip a caster into. The caster is held in place by a bolt that secures one side of the top plate. These pads are convenient for applications were excessive caster maintenance is required. Casters can be clipped in and out easily by simply taking out one bolt instead of 4 normally used to bolt on a caster.

Corner Bumpers

A rubber bumper that is in a 90 degree v shape, approximately 3" X 3" is reinforced on the inside by metal and has four holes that are used to screw it on to the corners of carts and equipment. Bumpers come in non-marking gray.

Seals

Plastic seals that keep debris out of raceways. Most seals are not heat resistant, so they should be removed from casters before used in a high-temp application.