I think I need to make one point clear from my previous post. The ball bearings are still taking all thrust loads present. The thrust bearings (fancy name for washers) are there to spread the load evenly and transfer it to the center race of the ball bearing. I looked for washers with very accurate center holes and found them in the form of thrust bearings. I even considered making my own washers as precision washers are hard to find in small quantities. Thrust washers are not hard to find in small quantities. The thrust washer also protects the bearing seals from the damage seen on the first set of bearings. And lastly, there is one more surface for rotation when it happens.
The best thing I did was my own machining of the ends of the screws. I now know for sure that the thrust faces are smooth and true. The scratches on the first bearings really bothered me how they got there. They were not there when the bearings were new. I now have a 1/16 inch thickness of protective leaded bearing bronze between the screw steel and the ball bearing shields on both ends of the screws.
The proof is the Y screws are now running much smoother and even faster. The “clean up” did what I thought it would do.
The strange thing is when I do something like this, I sort of get a “high” from having solved a problem. Drugs are a lazy persons way to a high. Much better to gain euphoria the old fashion way, earn it! 🙂