Swivel casters allow caster wheels to move in multiple directions, giving furniture on swivel casters greater ease of movement than furniture attached to rigid casters. It is important to consider aspects such as load carrying capacity, swivel caster and wheel dimensions, flooring materials and environmental conditions before selecting a swivel caster for any application.
Casters are tools that, when attached to an object, allow for the mobility of that object. While all casters allow for the linear motion of an object, only swivel casters allow an extra dimension of rotational motion to the objects on which they are installed. Swivel casters consist of a caster frame and a wheel; they are constructed so that the caster frame houses the wheel. When the wheel is installed into the caster frame, two legs are attached to either side of the wheel and the wheel is held in place between these two legs by an axle or bolt. Positioned above the legs is a swivel bearing, a component that provides the swivel caster with a full 360º range of movement. The swivel caster is commonly attached to equipment through a mounting plate, or top plate, that is connected to both the swivel bearing and to the two legs. Mounting plates generally contain four holes used to bolt the swivel caster to the equipment. Typical materials used for swivel casters include metal and plastic coated metal, which has the greatest load capacity; rubber, which allows for silent movement; hybrid rubber, which provides both silent movement and a high load capacity; and thermoformed plastic, which offers a high load capacity. In the past, all swivel casters used kingpins, both to attach the caster housing to the caster bracket and to provide pivot motion. Kingpins absorb a significant amount of stress, particularly in high-impact industrial applications, and they are consequently the number one cause of swivel caster failure. "Kingpinless" casters have become quite common among medical casters, office casters and even industrial casters. In kingpinless casters, a raceway of ball bearings connects the upper bracket to the caster housing in place of a kingpin. These are not only far more wear-resistant, but provide smoother swivel motion as well. As it true with the process of selecting any caster, careful considerations should be made in advance of selecting a caster in order to ensure its longevity and safety. Providing such considerations are made, a caster can be a valuable asset in its application for many years.