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2020-09-29
Linear bearings can vary widely in strength and size, and utilize bushings, grease, rails, balls, and slides. Although it is common for classification terminology to be imprecise concerning different commercial products, this problem tends to be pronounced when linear bearings are under discussion. As a result, this section will concentrate on sketching broad families of bearings as well as more common individual types.
Overall, linear bearings tend to be classified by two main elements: the type of rails they operate with and their method of adherence to such rails. Rails for linear guides generally fall into two basic categories: round rails or square rails (also known as profile rails). With regard to linear guides as whole (i.e. rails plus the moving carriage), three main types of linear bearings can be considered: linear ball bearings, linear roller bearings, and slide bearings.
Slide bearings or linear plain bearings are the most basic type of linear bearing. Their name stems from the fact that they operate by two surfaces sliding against each other. They perform linear movement and weight bearing using low-friction metals such as graphite and Teflon, as opposed to metal backing plates. Sliding contact in this type of linear bearing application should always occur between unlike materials, since this concentrates frictional wear in the softer material. Slide bearings are commonly found on oil production modules and heated pipelines, and in oil and water transportation and steel fabrication applications.
Slide bearings possess three basic designs: boxway, dovetail, and bushing. These designs primarily denote the configuration of the carriage that allows it to physically fit onto the rail. Bushing type bearings are particularly common. The term bushing refers to bearings that travel along rails using a cylindrical opening. Typically, such bearings contain two such openings that travel a pair of round rails. The walls of these openings commonly consist of materials such as injection-molded polymers, bronze infused with oil, or a type of powdered metal.