i have an mft template that has a series of 37.3mm circles every 96mm on center. the manufacturer's instructions are to use a 30mm router bushing with a 1/2" bit inside this 37.3mm hole template to cut the desired 20mm holes. problem is too much human error is introduced running the router around following the bushing on the template. (slight angle tipping, not getting perfect circles)
i want to cut a 37.3mm plug to fit exactly inside these holes in the template. from that plug, i'll drill a 30mm hole in the center with a forstner bit creating a ring (37.3mm OD and 30mm ID) and then i can use this new bushing ring around the factory bushing with a 20mm boring bit to keep everything perfectly centered.
i have pattern bits to make a copy of the hole, but i don't know how to go about making the opposite plug. any tips would be greatly appreciated!!!