In general,
plain bearings are the most simplistic type which come in the form of a bearing surface devoid of any rolling elements. In their most simplistic form, plain bearings are a shaft rotating in a hole, using the journal to slide over the bearing surface. With their design and construction, plain bearings are quite inexpensive, compact, lightweight, and boast a high load-carrying capacity. To construct such components, the most common materials used include babbit, bronze, cast iron, graphite, jewels, plastic, and bi-material combinations. Plain bearings may also go by various names when searching for such components, often referred to as either a
journal bearing or a bushing.
Plain bearings may come in a few forms, the most common being sleeve, flanged, and lined types.
Sleeve bearings in particular are a type in which a metal, fiber-reinforced composite, or plastic sleeve is implemented for the means of reducing vibration and noise. Often placed between parts that slide against one another, the sleeve bearing is well capable of absorbing friction while greatly mitigating noise at low speeds. Furthermore, they are also known for being cheap, requiring less maintenance, and providing an ease of installation. While capable of undertaking a high load capacity, the major benefit of such types is their shock load resistance due in part to their greater contact zone. While capable of benefiting a number of assembly types, sleeve bearings are most commonly found within the auto industry, off-road industry, marine industry, and food industry.
Flange bearings have an appearance similar to the sleeve bearing, albeit having a flange at one end. The flange is used for the means of providing a locating surface during the assembly process. A flanged bearing is capable of supporting loads through sliding motions, able to excel at low speeds with lighter loads. In some cases, the flange will be designed to a size that accommodates mounting holes for securing the flanged bearing in place.
Lined bearings are the final common type, simply being a bearing that utilizes a different material for its surface as a lining.
When choosing various plain bearings and sleeve bearings for a particular application, one should consider a few dimensional and operational specifications. The bushing clearance is the distance that the shaft moves when riding within the bushing, and it has an effect on thermal expansion. Generally, internal clearance should be chosen based on the mounting and operating conditions needed for operational clearance. Beyond such factors, a bearing’s length, diameter, loading, rotating speed, and PV value are all also important as each will determine how a particular bearing may fit into an assembly and how capable it will be for certain loads.
