.004 is pretty big, you should be able to cut that in half at least.
If it really is just from radial play in the couplers, you might try something other than the Lovejoy type. They can really suck sometimes. I really prefer the one-piece slitted stainless couplings. They may be pricey compared to the lovejoys, but not a big cost at all compared to the money you just spent on accurate ballscrews whose accuracy you can't use because of shoddy couplings! You could just try shimming the Lovejoys, but they will just wear again, and besides that your backlash can and will change under load as it compresses or deflects the spider - a problem you won't have with better couplings. Cheap Lovejoys are not a benefit to anyone! |