I was prepping stopper blanks today, had a mix of plum, maple and walnut. I'm starting with 1-3/4" square stock, between centers using a parting tool to turn a tenon for #2 jaws. The plum and the maple accept the parting tool nicely, and I get crisp shoulders. The walnut, however, shreds at the corners rather dramatically. I tried different parting tools, and starting angles to see if I can reduce the fray, but no luck. Any tips?