My interpolated holes are slightly smaller at the bottom.

So a cylinder that will slide in snuglly from the top won't fit from the other end of the hole.

I don't think this has anything to do with deflection because tried multiple finishing passes.

If the spindle were running out, that would make a bigger hole.

If the spindle were at an angle, the hole wouldn't taper.

So what's going on? Does this mean that the milling bit is smaller at the tip?