I designed a part with a 1/8" slot in it, knowing that I’d be cutting with a 1/8" bit. I was hoping outlining would enter that slot, but it would not.
Changing the width of the slot to .12501 allowed the bit to enter.
Just to clarify what kind of slots I’m talking about:
This is a known constraint. When you offset a polygon by the exact distance between two walls, it interferes with itself and cancels out, producing no line. I don’t yet have a good solution for this, but was hoping to add it as a feature as part of the tracing operation.
I figured it was known. Perhaps artificially reducing the bit size by some tiny fraction of it’s actual size during outlining? That couldn’t possibly have ripple effects, right? 
I assume that for drilling you just skip that step and force the operation.
changing the offset (i.e. reducing bit size) leads to a path that’s too close to the part, and thus inaccurate.
drilling is entirely different. it turns out there is a simple calculation for “circularity” that tells you if a series of points is basically a circle. and the center of that cloud of points is the circle center. so Kiri just looks for closed polygons with very high circularity whose diameter matches the selected bit.
