yeah i think you can find a jig a t lowes or menards or somewhere . best deal for router circle jig i have seen is thru rf ,http://www.rockfordf...=10105:54419:US
looks like there is a jig for your dremel 4000 . my first choice for this job would be a router though , don't know how you can round over or shape your rings with out one ether .
This is what i got so far before the ring cuts