Any drive which includes a rotating shaft uses bearings to support and
locate the shaft while still allowing rotation with minimum friction.
In table below only radial bearings are described. For most of the options listed, axial thrust bearing equivalents are available.
Additional information on bearings is to be found in the links below the table
|Plain Lubricated||Low cost bearing. Bearing made from alloy softer than shaft material. Lubrication required or progressive wear will result. Low radial space required. Smooth running. Bearing will always wear at start up and stopping when oil film lubrication (hydrodynamic lubrication) is not working. Length to Dia. ratio greater than 2 desirable.||Plain Bearing Mat'l Notes|
|Plain Porous||Plain bearing made from porous metal impregnated with lubricant. Will run for long period (+4000 hours) before re-lubrication of bearing required. Methods of continuous re-lubrication available.|
|Plain Dry||Same as plain bearing but bearing is able to operate with no lubrication. Based on either self lubricating material (PTFE) or on the transfer of solid lubricating film to shaft. This type of bearing more suitable for intermittent use. There is no way to prevent progressive wear|
|Plain Hydrostatic||This is a plain bearing with oil lubrication introduced under pressure. This bearing could operate for extremely long periods of time with no wear. Some bearings operating under a dual hydrodynamic/hydrostatic regime by machining the bearings to be self pressurising. Very low friction.|
|Deep Groove Ball||Low cost standard geometry bearings with balls retained in annulus between outer and inner race/rings. Very low starting friction. Can be supplied with seals/shields and filled with grease. The bearing eliminates the need for sleeves to protect the shaft form wear or damage. Relatively large radial space needed. Very small axial space required. Can provide both axial and radial location of shaft in housings|
|Cylinderical (Rolling)||Same principle as ball bearings but with cylindrical rolling elements. These are able to take much higher loads but can only resist support loading in a direction radial to the rollers. Requires lubrication. Generally used for large loads. No tolerance to angular deflection of shaft|
|Outer Race has spherical contoured bore. Bearings able to accept large angular displacement of shaft. High Capacity. Requires lubrication|
|Taper (Rolling)||Similar properties to cylindrical bearings but can accept a wider range of loads. Lubrication required.|
|Needle (Rolling)||Rolling bearing based on small dia. needle bearings. Very low radial space required. High radial capacity. Lower speed limits relative to ball bearings. Lubrication required.|
|Magnetic Levitation Bearings||Hi-Tech option requiring methods of monitoring the shaft position and controlling the magnetic forces|