see attached iges file.
It contains faces. The maximum gap that I can measure is 0.01825 mm.
I tried to sew it using Draw and I got an ACCES VIOLATION
here is what I did
igesread c:/temp/8_hole.igs 8h *
sewing 8hS 0.019 8h
I used 0.019 tol because I wanted to get a SH object without "holes" (I am assuming that OCC is just relaxing the tolerance locally)