been thinking about this for a while and finally tried it. i bought a set of road bike sugino maxy cranks of ebay for £15, the kind with the built in chainwheel and i made sure the bcd was 110. it was a 52 tooth ring and it also had a 40 tooth ring bolted to it with sugino bolts. here's what i did.
the cranks before.
bolted on a sugino spider to mark it
the lines to cut to
a dremel and 20 minutes later
the piece you cut off makes a nice ninja throwing star
going to polish then paint them candy red, should look nice and cheap too.