Thread: Pre load issues with BK bearings from LMB

Hi Guys

Thought i would post it here before i post to the zone. I know a few people have purchases ball screw and bearing blocks from LMB on ebay.
I have an issue trying to pre load and remove the end float from my ball screws.
I have a dial indicator mounted to the router base with the point on the end of the ball screw shaft. No matter how tight i do the pre load nut up on the ball screw i can not remove all the end float from the screw. I have around 0.13mm at the moment.
I have pressed out the bearings out of the block and have come to the conclusion that the "Made in China" brand of angular contact bearings that are used in these BK mounts are c%$p. They are manufactured with no in-built pre load (clearance between inner races) and no matter how tight you do the pre load nut up you will never remove all the end float of the screw in the standard state.
If i bolt the bearings together the other races have a far amount of slop. You can fit about 0.15mm between the two other races with the inner ones bolted together.
Also the bearings are mounted the the blocks in a face-to-face ( \ / ) configuration. After a little investigation and coming across a great page on the net, it seams that a face-to-face configuration is used when the inner race is 'fixed' and the pre load of the bearings is adjusted by pressure on the outer race. This is not going to happen with the BK blocks.

So i see i have to options (if i don't want to buy new bearings)
1. Leave them in the face-to-face config and shim the inner race. I was think of 0.2mm which should remove the 0.13mm float and add a bit of pre load.
2. Flip the bearings so they are back-to-back, shim the other race and then the nut on the ball screw can be used to adjust the pre load?

Has anyone had experience with these sorts of issues?

Thanks