Little Machine Shop Mill Gib Replacement

[papermaker]

I am wondering if anyone has had any experience with replacing the steel gibs on a x2 mill. Specifically with another material other than steel. My mill has been converted to CNC using the CNCFusion ballscrews and nuts. I actually have two issues. If I adjust the gibs so the cuts are smooth then they are to tight to travel the length of the Y axis. I'm wondering if another material would work better than the steel ones it came with. I know most lathes use brass for gibs. Would there be any negatives from using brass.
My second problem also involves the Y axis . The ballscrew nut is held in place by a set screw. If it is not in the exact correct spot it jambs the ballscrew and consequently I start losing steps.

Any help with either or both of these issues would be appreciated!

 

[DMS]

I think the gibs are actually cast iron, which is what most larger machines use. The problem is they are probably pretty rough. If you pull them out, you can get a good look at them. I have heard of some folks lapping the slides and gibs with reports of improvement. I also recall a lot of discussion of adding a thrust washer on the feed screw. Apparently the default arrangement is pretty high friction. If you replaced your leadscrew mounts with ball-bearing mounts, disregard that last comment, but if you have not, it may be a win-win.

As far as the Y nut, not sure I am picturing the setup. This set-screw is underneath the table right?

 

[papermaker]

I wished that I had taken pictures of the Y axis ball nut when I installed it. It has a tab attached to the top of the nut and the set screw tightens against it. The ballscrew itself has a bearing in the end towards the front of the mill. There is quite a bit of slop in the ball screw when the set screw is loose so trying to pinpoint the exact spot to have it is hit or miss.

On the plus side I took the gib out of the Y axis and lapped it with some 600 grit wet sand paper and got that smoother. When I put things back together I put a .005" shim on the bottom of the way before adjusting the gib screws. I seems to be working just fine for now but would still like to explore using another material for gibs.