As you may remember, I've been making prototype printed circuits on my Taig micro mill. I was pretty well stuck, not being able to get traces small enough. It didn't seem to matter much what my z depth was, the conical bit wouldn't cut a line that was anywhere near as narrow as its 0.1mm tip.

Then one day, it dawned on me that that the head was vibrating like a sonofabitch. I mounted a dial indicator on the bed and positioned the plunger on the head. There was +/- .003" of vibration! pretty much a killer when trying to mill lines less than 0.008" wide.

I have since replaced the whole headstock with a 1.5KW 400Hz spindle motor. It runs up to 24,000 rpm and there's no detectable vibration. This is great. Of course, now that that problem is fixed, it made others more visible. I noticed that lines in the +Y direction were a different width than those in -Y. This turned out to be loose gibs, so I took apart the whole XY mechanism, tightened the nuts to remove all but 0.0005" of backlash in X&Y which I had previously compensated for in mach3, and adjusted the gibs properly.

All I can say is that I wish I had taken the time to do these things from the get-go. What a difference. Next (after I get some work out of the way), I'll do the same with the Z axis.