Two case history examples point to need for caution with metal spray
At my service center, we have seen problems with previously repaired shafts that were metal sprayed. In these cases we received motors for overhaul. Upon inspection and measuring the bearing shaft fits, we found something that just didn’t “feel” right. We could tell from the appearance that the shafts had been repaired prior to the current overhaul.
Two case histories point out the need for caution when working with metal sprayed shafts:
- Example 1: When measuring the bearing fit shaft size, the micrometer didn’t feel right; mushy, not solid, although the journal was very close to the specified size. After using two micrometers to experiment with one of these frosted fits, it was discovered that the measurement on one micrometer changed when tightening down the other micrometer and vice versa.
- Example 2: The bearing journals on a large armature began to fail while the armature was coming up to speed in balance stand.
Download and read the article for full details of each case study.