Using FreeCAD instead of OpenSCAD to take advantage of the inbuilt sprocket generator:
My choice of 77 teeth
is cutting it close, on #25 chain pitch, with such a large 130mm BCD crank. It's just a ring of material at this point; the bolts are very nearly at the teeth themselves.
For a fixed gear bicycle I probably don't need to chamfer the teeth, do I? Not terribly difficult in a CNC sense, I'm sure, but the problem is more that I have no idea how much to add - sprockets are standardized but the choice of chamfer on a bicycle chainring seems to be a dark art wrought from
rumours and wild guesses the needs of derailleurs and/or narrow-wide teeth width patterns.
Anyway, can't be hard to file down if it turns out flat teeth get stuck or something - could just install it and spin the crank against a file as a "poor man's lathe".
Any mech engs in the house want to venture an opinion?