Supplied B1 Module 07A textbook: PDF pages 247–254.
Bearing types and loads
Plain bearings support relative motion across sliding surfaces, while rolling-element bearings use balls or rollers between races. Radial loads act across the shaft axis; axial or thrust loads act along it. Different designs combine these capabilities in different proportions. A deep-groove ball bearing, tapered roller bearing and thrust bearing are not interchangeable merely because an outside diameter matches. Confirm the specified designation, internal clearance, seals and application. The bearing arrangement also determines how thermal expansion and location are controlled.
What is an axial bearing load? A load acting along the shaft axis.
Cleaning and preservation
Use the prescribed cleaning agent and process, keeping bearings and tools free of abrasive contamination. Sealed or prelubricated bearings may not be intended for shop washing or relubrication. Protect cleaned parts from corrosion and dirt immediately. Do not spin a bearing with a compressed-air jet: uncontrolled speed and lack of lubricant can damage it and create a safety hazard. Keep matching components together where required. Cleanliness is especially important because a very small particle can damage a loaded rolling contact.
Why should bearings not be spun with compressed air? Uncontrolled dry rotation can damage them and create hazards.
Inspection and defect recognition
Inspect races, rolling elements, cages, seals and mounting surfaces for corrosion, cracks, scoring, pitting and overheating. Roughness, excessive play or a damaged cage requires assessment. Brinelling is indentation associated with concentrated loading; false brinelling arises from small oscillatory movement and fretting. Spalling is material flaking from the raceway or element surface. A bearing may feel smooth without load yet fail under operating conditions, so use the specified inspection and test rather than a hand-spin check alone.
What is bearing spalling? Flaking or breaking away of surface material.
Lubrication requirements
A lubricant separates surfaces, reduces friction and carries away heat or protects against corrosion according to the bearing design. Use the exact grade and quantity required. Too little lubricant can allow contact and overheating; too much grease can cause churning and heat. Do not mix greases unless approved. Contaminated lubricant can become an abrasive rather than protection. Some bearings use oil supply systems, others use grease or sealed lubrication; servicing one type as though it were another can cause failure.
Why can overgreasing be harmful? Churning can generate heat and damage seals.
Installation and removal
Use suitable pullers, presses or thermal methods as specified. Apply installation force to the ring that has the interference fit and support the mating part. Loading through rolling elements can mark the raceways. Inspect shaft and housing fits, cleanliness and retaining components before assembly. Do not use direct uncontrolled hammering. Heating limits depend on bearing materials, seals and the approved process. After temperatures equalise, verify the required seating, end float or preload.
Where should fitting force be applied for a bearing pressed onto a shaft? To the inner ring with the interference fit.
Interpreting failures
Bearing damage can reveal incorrect lubrication, contamination, poor fit, misalignment, overload or electrical erosion. Replacing the bearing without addressing its cause may repeat the failure. Record the location and appearance of defects, inspect associated surfaces and review the operating conditions. A bearing installed with the wrong clearance or excessive preload may overheat even with clean oil. Use the maintenance data to determine acceptable clearance and post-installation checks. Evidence should connect the failed component with the system that supports it.
Why investigate the cause of bearing damage? A replacement may fail again if the underlying cause remains.
Apply the knowledge
Work through these examples before starting the quiz. Explain why the other choices would not meet the requirement.
A bearing was pressed onto a shaft using force on its outer ring. What is the concern?
Load transmitted through rolling elements may mark raceways — Fitting loads should act on the interference-fitted ring.
A greased bearing runs hot after excessive servicing. Which cause is plausible?
Grease churning — Excess grease can generate heat and affect seals.
Small repeated movements leave wear marks resembling indentations. Which defect is associated?
False brinelling — Oscillatory fretting can produce false-brinelling damage.
A sealed bearing has no authorised cleaning procedure. What should be done?
Follow its specified maintenance or replacement instructions — Sealed bearing construction and servicing restrictions must be respected.