x-axis leadscrew nut

[mjarus]

I just exchanged my mini-mill because the last one had issues with the table (see my other post around here somewhere...). Anyways I got the new one home and tore it down to clean it. When I did, I noticed that the x-axis nut was waaay loose, so I just tightened it. When I went to put the x-axis back on the lead screw would not engage, so I loosened the hex heads that hold the nut, and it went on fine. I got it up on the bench to adjust the gibs and it just didn't feel right no matter what I tried so I removed the table and the lithium grease that I put on the leadscrew was a copper color. I thought uh-oh... shavings from the brass nut.

So I cleaned up the lead screw and put it back in and loosened the nut again. Then I adjusted the gibs with the nut loose, then tightened the nut... feels perfect. However I still notice that there is a copper tinge to the lithium grease.

So...

1) Is the discoloration in the grease the new nut settling in or is this bad?
2) How are you supposed to adjust the leadscrew nut? Did I do this right?

On another note: The second machine seemed a lot more "dirty" than the first. There was grit and swarf everywhere... I mean waaay worse that the other machine was. A lot of the red grease actually came out black! Last time I didn't remove the saddle, the time I HAD to...

Thanks for any help on this.
mjarus.