A stock 6204 single row deep groove ball bearing was cut apart for inspection. Before dis-assembly, the bearing seemed tight, and the side seals appeared intact. The bearing was taken from a used replacement IMS shaft with unknown history. There was oil in the IMS shaft tube when the bearing was removed. This picture shows the bearing upon removal from the IMS shaft. the seal looks good.
Taking off the side seal, the interior was filled with what could best be described as brown oily goo. It appeared to be slightly thicker than motor oil.
Cutting apart the bearing to inspect the inner races revealed a series of equally spaced scuffed lines running across the bearing race. These appeared to be discrete areas of fine pitting on the races. There were 8 lines on the inner race, and 7 lines on the outer race. This is the inner race:
and this is the outer race - and a bottle of wine, think I'll have a glass after this post:
This looks like the very beginning of the bearing failing. The 8 balls in the bearing looked like the finish was going and there was at least one noticeable scratch evident. My sense is this bearing is failing due to contamination and improper lubrication - low speed operation with too low of a viscosity lubricant.
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