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Originally Posted by
LongRat
These blocks have turned out to be a bit of a nightmare. After checking the Y it turned out to be exactly the same. But I still wasn't happy with the Z either, even after the skimming.
A couple of days of investigation have yielded the following information. The blocks were machined to the correct depth all along, but there should be a washer or shim separating the outer races of the two bearings in the bore. My understanding is that angular contact bearing pairs are made such that there's a small gap between preloaded races, so when you compress them together this gap is closed up and gives you your defined preload. I am certainly no expert though.
In my case the races to be preloaded were touching all the time, meaning that no external force could ever apply an axial load from inner to ball to outer race. Placing a turned washer, 1mm thick between bearings solved this issue, and it meant that the facing cut I made across the block was unnecessary. This leads me to believe that they should have been supplied with some sort of spacer washer. Or maybe they ripped off the design from elsewhere and neglected that part.
Another clue to the nature of these bearing blocks comes from the faint scored lines crossed where the mounting holes are. They have been marked out - the blocks are drilled manually!