Tapered Roller BearingsFacts & Failures

Standard Terms for Tapered Roller Bearings

A. Roller Bearings

B. Roller Cage

C. Inner Race

Standard Terms for Tapered Roller Bearings

D. Outer Race

Tapered Bearing Loading Patterns

Normal loading. When the bearings are installed properly, with the correct bearing pre-load, the load pattern will be symetrical (blue area). Improper loading. Overtightening the adjusting nut, or not seating the bearing properly, causes a shift in the load pattern on the bearing surfaces.

Improper Bearing AdjustmentIf larger end of roller shows smearing, spalling or galling, bearing adjustment is too tight.

Spalling - when the surface breaks up into chips or fragments.

Galling - when the surface is broken by friction or abrasion

Improper Bearing Adjustment If the end of the roller is spalled, the roller has been running against the inner ring. The inner ring has flanges on each edge to keep the rollers in line. If the bearing is overloaded (tightened too hard) during adjustment, the edges of the rollers will ride against the flange, producing the wear you see here.

Improper Bearing Adjustment

If you see wear, smearing or spalling, on the small end of the roller, it indicates that the bearing adjustment is too loose.

Improper Bearing Adjustment

When the race is worn, it indicates that the bearing may have been overloaded.

Misalignment

When bearings are in proper alignment their center lines are parallel to each other.

Misalignment

If the bearings are not seated properly their center lines will be at an angle to each other.

Causes of cocked bearings:

dirt or burrs preventing a flush mount

outer cup installed without proper tools

a warped shaft

Effects of Contamination

Scratch marks in the surface of the race are caused by hard particles in the lubricant.

Effects of Contamination

Etched metal surfaces are usually the result of water contamination.The water allows oxidation and the metal becomes pitted and porous.

Effects of Contamination - rollers

Scoring around the rollers indicates contamination of the lubricant by dirt, girt or metal particles.

Effects of Improper Lubrication

When metal appears to be flaking off across the full surface of the race, suspect there is a lack of proper lubrication.

Effects of Improper Lubrication

Discolored steel anywhere, on the cup, cone or roller, indicates overheating.

Installation Damage

The rib of this cage design has been bent out of round. Even small distortions of the assembly can destroy a bearing.

Installation Damage

Nicks and dents. Damage like this dent in the cage or retainer is the result of a sharp tool being used to install or seat the bearing. A drift or screwdriver used on a bearing is guaranteed damage.

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