Hi everyone. I got a great deal on a used 440. This is my first ever machine, never operated any machine before. I found that I had ~0.0025” of lost motion on my x axis. I decided to loosen up the gibs too see if they were too tight. That got me down to ~0.0012” of lost motion. Is this an acceptable amount? Like, my gibs aren’t too loose now, are they? Should I continue to tighten them until lost motion goes up to say 0.0015” to see if they’re engaged properly?
Edit: I haven’t yet checked how this has effected my y axis, I will do that when I get home today.
Ball screws are not used in a static state. The backlash you see by using an indicator and stepping back and forth becomes irrelevant when the screws are loaded in the direction of travel. Instead of obsessing with an indicator have the machine cut a circle and measure the circle. Then cut the circle .025 bigger and see if it increases in size by .025. I think you will find the machine to be perfectly capable.
You can download the machine’s user manual from Tormach PCNC 440 Documents and you’ll find the advanced maintenance covers measuring the lost motion and adjusting.
From what you’ve said, it would appear that it’s the angular contact bearings that require some adjustment. On a 440, those bearings are integral with the motors and are adjusted with a pin spanner that engages on the rear of the motor housings.
0.0012" isn’t crazy bad, but you can do better. They’re certainly better than that from new,