Have a set of them I use for seat tubes. For your requirement they are just the thing. With each adjustment one removes only the tiniest bit of metal so there is no danger of going oversize. They are too slow/tedious to employ if one wishes to enlarge the seat tube to accept a larger diameter pillar. Always remember to use plenty of cutting oil.

Suspect your zig-zag marks may be coming from the corners of the binder ears. When the binder is tightened these can be pushed into the pillar.