[inov8r]

Your spindle can grow with heat, and see changes of .001". Try warming up your spindle before you set your Z height and see if that helps.

Here is a little update on some testing I have been doing. The pic is of a series of cuts to help me find some depth inconsistency I have been having. You can't see in very well in the pic but I started with a square in the center that was set to cut .0001", this would let me know if I was zeroed correctly. And it scratched the surface perfectly. The circles and moon shaped cuts in each set were all cut to the same depth and overlap so I could see any major depth issues within a set (none found.) The top set is cut .001" and ended up a little under. The second set was cut .002" (2 passes @ .001") and ended up slightly under. Set 3 cut .003" (3 passes @ .001") and ends up a few tenths over. Set 4 cut .004" (4 passes @ .001" ) and ends up a few tenths over .005". Set 5 cut .005" (5 passes @ .001") and ends up .0075". Set 6 cut .005" (1 cut @ .005") also ends up .0075.

The logical conclusion was to recheck for an expanding spindle. I'm not sure what I was doing so wrong before but I put an indicator on and let it run till it warmed up nicely and low and behold it grew over .002"!! I am using the speeder and I suspect the aluminum housing has a lot to do with this much expansion.