Ball and Roller Bearings

Ball and Roller Bearings

When removing and installing bearings, ensure that the following practices are observed to ensure component serviceability.

• Remove all traces of lubricant from bearing under inspection by cleaning with a suitable degreasant; maintain absolute cleanliness throughout operations.
• Conduct a visual inspection for markings on rolling elements, raceways, outer surface of outer rings or inner surface of inner rings. Reject any bearings found to be marked, since marking in these areas indicates onset of wear.
• Hold inner race of bearing between finger and thumb of one hand and spin outer race to check that it rotates absolutely smoothly. Repeat, holding outer race and spinning inner race.
• Rotate outer ring gently with a reciprocating motion, while holding inner ring; feel for any check or obstruction to rotation. Reject bearing if action is not perfectly smooth.
• Lubricate bearing with generous amounts of lubricant appropriate to installation.
• Inspect shaft and bearing housing for discoloration or other markings which indicate movement between bearing and seatings.
• Ensure that shaft and housing are clean and free from burrs before fitting bearing.
• If one bearing of a pair shows an imperfection, it is advisable to replace both with new bearings; an exception could be if the faulty bearing had covered a low mileage, and it can be established that damage is confined to only one bearing.
• Never refit a ball or roller bearing without first ensuring that that it is in a fully serviceable condition.
• When hub bearings are removed or displaced, new bearings must be fitted; do not attempt to refit the old hub bearings.
• When fitting a bearing to a shaft, only apply force to the inner ring of the bearing. When fitting a bearing into a housing, only apply force to the outer ring of the bearing.
• In the case of grease lubricated bearings (e.g. hub bearings) fill the space between bearing and outer seal with the recommended grade of grease before fitting seal.
• Always mark components of separable bearings (e.g. taper roller bearings) when dismantling, to ensure correct reassembly. Never fit new rollers in a used outer ring; always fit a complete new bearing assembly.

Oil seals

Always renew oil seals which have been removed from their working location (whether as an individual component or as part of an assembly). NEVER use a seal which has been improperly stored or handled, such as hung on a hook or nail.

• Carefully examine seal before fitting to ensure that it is clean and undamaged.
• Ensure the surface on which the new seal is to run is free of burrs or scratches. Renew the component if the original sealing surface cannot be completely restored.
• Protect the seal from any surface which it has to pass when being fitted. Use a protective sleeve or tape to cover the relevant surface.
• Lubricate the sealing lips with a recommended lubricant before use to prevent damage during initial use. On dual lipped seals, smear the area between the lips with grease. Note: some oil seals are coated with a protective wax and must be fitted dry, unless instructed otherwise.
• If a seal spring is provided, ensure that it is fitted correctly. Place lip of seal towards fluid to be sealed and slide into position on shaft. Use fitting sleeve where possible to protect sealing lip from damage by sharp corners, threads or splines. If a fitting sleeve is not available, use plastic tube or tape to prevent damage to the sealing lip.
• Grease outside diameter of seal, place square to housing recess and press into position using great care, and if possible a ’bell piece’ to ensure the seal is not tilted. In some cases it may be preferable to fit seal to housing before fitting to shaft. Never let weight of unsupported shaft rest in seal.
• Use the recommended service tool to fit an oil seal. If the correct service tool is not available, use a suitable tube approximately 0.4 mm (0.015 in) smaller than the outside diameter of the seal. Use a hammer VERY GENTLY on drift if a suitable press is not available.
• Press or drift the seal in to the depth of its housing, with the sealing lip facing the lubricant to be retained if the housing is shouldered, or flush with the face of the housing where no shoulder is provided. Ensure that the seal does not enter the housing in a tilted position.