The spalling of one side limit position of gully is mainly manifested in the serious spalling ring at the junction of gully and retaining edge. The cause is that bearings are not installed in place or axial overload occurs during operation.

The countermeasures are to ensure that the bearing is installed in place or to change the free side bearing outer ring fit into clearance fit so that the bearing can be compensated when the bearing is overloaded.

If the installation cannot be ensured, the direct contact of the bearing can be reduced by increasing the film thickness of the lubricant (improving the viscosity of the lubricating oil) or reducing the load of the bearing.

The symmetrical position of the inner ring is the surrounding band peeling, and the outer ring is the circumferential symmetrical position peeling (that is, the short axis of the ellipse), the main reason is because the shell hole ellipse is too large or the two halves of the separated shell hole structure, which is particularly obvious in the motorcycle camshaft bearing.

When the bearing is pressed into the shell hole with a larger ellipse or the two halves of the separated shell are fixed, the outer ring of the bearing produces an ellipse, and the clearance in the short axis direction is significantly reduced or even negative.

Under the action of load, the inner ring rotates to produce circumferential spalling traces, while the outer ring only produces spalling traces in the symmetrical position of the short axis direction. This is the main reason for the early failure of the bearing. The inspection of the failed parts of the bearing shows that the roundness of the bearing’s outer diameter has changed from 0.8um to 27um under the original process control. This value is much larger than the radial clearance value.

Therefore, it is certain that the bearing works under severe deformation and negative clearance, and the working surface is prone to early abnormal sharp wear and spalling.

The countermeasures are to improve the machining accuracy of shell holes or to avoid the separation of shell holes as much as possible.

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