I've noticed that I have 0.086" backlash on the Z axis on my SX3 machine. I get about the same value from the spindle or the head block so that rules out the spindle assembly.
I believe the backlash comes from the coupler over the Z axis ballscrew under the back cover plate.
My question is how to adjust out the backlash? I know the four screws need to be tightened, but, how much and how do I know how much?