Perfect circle every time. Remember just because you have never seen it done before doesn't mean it hasn't. I have used this method several times including once when I cut 2 inches of glass and epoxy. (link below) ...
by Bronzepony Beaded Jewelry
by Kaylee B
by New Stitch a Day: Knitting and
by Feride Erbasar
by Justin's Toys - Toys, Gifts,
by Etsuko Watanabe
by Missouri Star Quilt Company