Bearing Failure RCA: Fracture


When a rolling bearing is damaged during machine operation, the entire machine or equipment can seize or malfunction. Since bearings that fail prematurely or unexpectedly cause trouble, it is important to be able to identify and predict failure beforehand, so that preventive measures can be adopted.

Damage Condition

Fracture refers to small pieces which were broken off due to excessive load or shock load acting locally on a roller corner or rib of a raceway ring.

Possible Causes

  • Impact during mounting
  • Excessive load
  • Poor handling such as dropping


  • Improve the mounting method (shrink fit, use of proper tools)
  • Reconsider the load conditions
  • Provide enough back-up and support for the bearing rib


Fracture 1

Part: Inner ring of a double-row cylindrical roller bearing
Symptom: Chipping of the center rib
Cause: Excessive load during mounting


Fracture 2

Part: Inner ring of a tapered roller bearing
Symptom: Fracture of the cone back face rib
Cause: Large shock during mounting


Fracture 3

Part: Inner ring of a spherical thrust roller bearing
Symptom: Fracture of the large rib
Cause: Repeated shock load


Fracture 4

Part: Outer ring of a solid type needle roller bearing
Symptom: Fracture of the outer ring rib
Cause: Roller inclination due to excessive loading (Needle rollers are long compared to their diameter. Under excessive or uneven loading, rollers become inclined and push against the ribs.)


Source: NSK