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Plain Bearings

Plain bearings are bearings that sit between the shaft and housing and support rotating or reciprocating shaft motion through sliding surface contact. Compared with rolling bearings that use balls or rollers, they have a simpler structure, can be installed in a thin and compact space, and are relatively resistant to shock loads. Materials include copper alloys, sintered oil-impregnated alloys, and resin-based types using PTFE (fluororesin) and other polymers. Many resin-based types can be used without lubrication, and conductive grades for underwater and chemical-liquid use, as well as antistatic applications, are available. Shapes include straight, flanged, and slit liners that are easy to install. They are used in rotating and sliding parts of automotive components, food machinery, and conveyor equipment. This category also includes radial ball bearings for vacuum and high-temperature use.

How to choose Plain Bearings

  1. 1. Select dimensions that fit the shaft diameter and housing bore

    Match the inside diameter d to the shaft diameter and the outside diameter D to the housing bore diameter. Listed products have inside diameters of 3 to 70 mm and outside diameters of 5 to 80 mm. When press-fitting, allow for the bearing shrinking during installation, which reduces the inside diameter. Also check the shaft and housing tolerances recommended by the manufacturer.

  2. 2. Verify bearing pressure and speed using the PV value

    Confirm that the PV value, which is the product of bearing pressure (load divided by projected area) and sliding speed, does not exceed the limiting PV value. The limiting PV value of listed products is 400 MPa·m/min. The individual limits for bearing pressure alone (3 to 10 MPa) and for sliding speed alone (150 m/min) must also be satisfied.

  3. 3. Determine the length according to the load

    Increasing the length L increases the projected area and lowers the bearing pressure. However, if the length is too great, shaft deflection tends to concentrate the load at the ends, causing edge loading. Listed products have lengths of 3 to 60 mm, so select a length that keeps the bearing pressure within the limit.

  4. 4. Select a material suited to the operating environment

    For underwater or chemical-liquid use, choose a material with chemical resistance and wear resistance in liquid. Where static electricity is a concern, choose a conductive material. Wear of the mating material also varies with the material and hardness of the mating shaft. If antistatic performance is required, also check the volume resistivity.

  5. 5. Check temperature and operating clearance

    Resin bearings expand as temperature rises, which reduces clearance. In addition to the maximum operating temperature (300 to 350 °C) and continuous operating temperature (260 °C), maintain the recommended minimum operating clearance (0.095 to 0.195 mm).

  6. 6. Match the lubrication method to the maintenance conditions

    Whether a bearing can run without lubrication, or requires oil-impregnated or external lubrication, affects maintenance effort and the risk of contamination in the surroundings. Greaseless types are suitable for food machinery and clean environments. For use in vacuum, also check the usable vacuum level and low outgassing performance.

This guide was written by AI based on the listed products' documents and specification items. Check each manufacturer's documents before adopting.