Boy! Whata’ Drag

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Here are the pictures of both pair of Y axis bearings. The drag I suspected wasn’t on the outside case edge but right in the middle of the shields. I most likely started this problem when I was experimenting with end thrust. I have replaced these but not tested the new bearings yet. I’ll do that this weekend.

I found a source for some 1/16″  thin solid thrust washers if I have to use them. They are available in several types of material and the center hole is very accurate.

One shield shown here is actually dented. I don’t know what caused that but it had to be a very hard stop or tapping on the bearing. This was also on the Y axis screw shaft that was factory supplied turned slightly undersized (loose rather than slip bearing fit.)

I also note the scraping is not 360 degrees on the bearings. That indicates some shaft/bearing misalignment. That is a big clue.

The lesson learned is to keep the preload as close to zero as possible. Mine were and are now set where I can turn the holding screws at their heads and the nylon lock nuts will turn if they are not held. I have had them a bit tighter when I first set up the machine, which I soon discovered is incorrect. A thin thrust washer may have prevented the digging in scrape. I’ll also make sure the end cover (pressure) plate holding screws are adjusted equally side to side (a part of bearing alignment).