Reading failed bearings
Symptom to cause lookup for rolling bearing failures
A single table that connects what you see on the part with the usual cause. Start here when you hold a failed bearing.
How to use it
Find the family, then match the look. Use it as a first pointer and confirm with measurements and operating history.
| What you see | Usual cause |
|---|---|
| Fretting corrosion or creep on inner ring bore | Interference with the shaft too small |
| Scuffing on inner ring bore | Interference with the shaft too large |
| Smearing on the raceway | Preload too high or wrong |
| Seizure at roller ends and inner ring rib | End play too small at assembly |
| Symmetrical fretting on upper and lower sides of the ring | Misalignment |
| Broken cage on a ball bearing | Abnormal load from misalignment, excessive vibration or impact |
| Flaking on opposite faces of the raceway | Diagonal assembly |
| Broken cage, flaking at ball pitch, cracks and chips | Impact load, indentation that grew into flaking |
| Indentations on the raceway | Foreign matter or flakes from another bearing |
| Smearing and wear on rollers | Lubricant contaminated by water or other foreign matter |
| Heat colour on raceway and cage guide surfaces | Wrong lubrication method or lubricant |
| Scuffing on roller end and rib | Lubrication failure |
| Dents on the cage | Impact on the cage during handling |
| Scratches and scuffing on rollers, flaking at roller pitch | Careless handling in assembly |
| Rust at roller pitch | Bearing left unused in moist conditions |
| Rust on one row of the raceway | Water in the lubricant in operation |
| Electrical pitting or ridges and staining on balls, rollers and rings | Current through the bearing |
Takeaway. Use the table to form a hypothesis, not a verdict. Then look for a second piece of evidence that supports it.
Put it to work in the tool