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There are several important dimensional specifications for plain bearings and sleeve bearings.

Bushing clearance is the distance in the radial movement of the shaft that rides within the bushing. The operational clearance is different than the initial internal clearance. The initial clearance is always greater than the operational clearance because the bushings are expanded or compressed by interferences fits. This causes differences in thermal expansion of the nsk bearing rings and mating components. When selecting a plain or sleeve bearing, the internal clearance should be selected based on the appropriate mounting and normal operating conditions to get the suitable operational clearance. 

Bearing ID and OD is the inside diameter (ID) and the outside diameter (OD) of the bushing, not including the flange.

Length describes the overall length of the plain or sleeve bearing.

Loading of the bearing is important to calculate when making a selection. The maximum load a of a bearing is given as pounds per square inch with the maximum load capacity for static of load speed applications being 1/3 of the bearing materials compression limit.

Rotating speed rating is related to several factors, such as bearing material, lubrication, alignment, shaft surface finish and shaft hardness.

PV value is the product of the specific load (P) and the sliding speed (V). It has a significant influence on the service life of the bushing and is important to consider when designing around the application. The lower the PV value the longer the bushing's life.

Plain bearings are used for high radial loads (perpendicular to the axis of the shaft) and low to high speeds. Typical applications include turbines, large milling systems, engine cranks, compressors, gearboxes, [sleeve bearings] supports, etc.The components that are separated by the oil film in a plain bearing are the bearing liner and the shaft. The shaft is composed of high-quality, wear-resistant, structurally strong steel. The bearing liner may be made of a single layer or multiple layers, depending on the design features of the equipment 

Under normal operating conditions, the lubrication regime will be a hydrodynamic full-fluid film. A hydrodynamic film occurs when there is sufficient lubricant between the lubricated surfaces at the point of loading to form a fluid wedge that separates the sliding surfaces. In this state, the lubricated components do not touch each another, reducing friction and wear.Another condition that can occur is boundary film lubrication. This is when the film that separates the surfaces undergoes significant loss resulting in a high load of metal-to-metal contact. This happens any time the relative motion of component surfaces are slow and no oil film is formed.

Operating under proper speed, surface area, viscosity and oil volume, a plain bearing can support very heavy loads. The balance between these conditions is important. If the load or the speed changes, the lubricant viscosity must be adjusted to compensate for the change. There is no simple formula that is used to calculate the viscosity requirements for oil lubricated plain iko bearings, but the ZN/P formula demonstrates the results of complex calculations used to arrive at the proper clearance. 

There are several factors that can wipe or damage a plain bearing surface. Abrasive wear is one of the most common. If the wear is caused by a hard particle rubbing between the lubricated surfaces, it is called three-body wear. Wear caused by an asperity on one surface cutting the other surface is called two-body abrasion