No. 10

Case History: Bearing Cage

The illustrated bearing cage was manufactured as a sand casting requiring extensive secondary machining to provide the tolerances needed for proper functioning. In addition, problems were encountered when crimping the ears to hold the balls in place. The inconsistency in the sand-cast alloy caused breakage.

PIAD's objective was to eliminate all machining and provide a material with sufficient ductility to prevent breakage when crimping.

In consultation with S.K.F. design engineers, tolerances on the pockets as well as for the pitch diameter were established which allowed proper functioning and were achievable by PIAD in the as cast condition. The total as cast tolerance on the ball pocket radius is being held at ± .0035" and the pockets are co-plane within .010". The as cast surface finish in the ball pockets does not exceed 63 R.M.S.

The material chosen by PIAD is a lead free yellow brass (PIAD alloy M010) with a minimum elongation of 40%.

All machining operations as well as breakage of the ears when crimping have been eliminated.

The stated objectives were accomplished.

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