Repairing plain bearings of large surface grinding machines

The professional overhaul of plain bearings on large surface grinding machines is carried out in several steps:

1. Repair the spindle journal: Restore roundness, taper, surface roughness and the alignment of the front and rear bearing journals of worn spindles. In general: a spindle re-ground using the fine grinding method achieves better quality than one repaired by lapping.
2. Inspect and repair the bearing bore: Using a precisely manufactured tapered test gauge, check the tapered bore in the housing and bring it to form tolerance.
3. Re-grind the outer taper of the bearing: Using the tapered bore of the housing (or bushing) as a reference, the outer taper of the bearing is re-ground until the contact surface reaches at least 80%. During fine grinding, the bearing bushing sits on a mounting mandrel whose outer diameter corresponds to the re-ground spindle diameter; the bearing bore is adjusted so that it slides freely on the mandrel.
4. Scrape the bearing bore: After repairing the spindle and outer taper, the bearing bore is scraped. A lapping mandrel is used instead of the spindle, whose dimensions correspond to the actually repaired spindle and bearing bore dimensions. After reaching the required contact point distribution, the bearing bore is adjusted to a slightly sliding fit on the lapping mandrel. The bearing then remains in the housing and is cleaned there; afterwards, running-in is carried out with chromium oxide as lapping compound to remove scores and burrs from the scraping process.

Since bearings of this design only deform elastically to a limited extent during operation, deformation grooves are additionally deepened or widened, equally sized bamboo or fitting pieces are inserted into each groove, or additional axial grooves are introduced to force uniform deformation. This technique is the basis of later multi-segment plain bearings.

Conclusion: Plain bearing overhaul requires experience and precision – at our company, specialists perform these jobs with the necessary care.