hI,
I have 2 ball screws with 22mm end that I need to connect to stepper motor
shaft 11mm, I dont want to grind the ball screw down to 12 mm so I need a couple of spider type zero back lash couplings that are not to expensive, can you advise me where to source.

also does it matter about the angle of the double row angular contact bearings
when used with ball screws.

thanks in advance for help.

First of all, did someone size the motor to your machine? Direct drive was popular back in the stepper motor days, now with DC and AC servos, they usually use a timing belt with gear reduction so the motor makes about 10 turns per inch. Unless you have stepper motors, direct drive may be like taking off in 2nd gear in your car! Try http://smp.applied.com/, they sell everything you need.

secondly, heck ya it makes a differance how you install the bearings! on ANY thrust bearing, look at the outer race, one side will be thicker than the other. The thick side of the outer race of the 2 bearings wants to be "back to back", that way you can push them in and out of the bearing journals. Also if they are not "back to back, but both aimed the same direction, they will pop apart when you are machining, and you will have bigtime backlash.

Good Luck with your prodject