I needed to upgrade my router mounting plate to accept removable center inserts, as I bought a slot-cutter which wont fit the original 1-inch center hole. My dilemma was how to make a 4 inch circular template to use with a PC guide.
After a bit of brainstorming, I came up with this jig, consisting of a piece of 1/2 inch MDF with a 1/4-20 FH for a pivot, screwed into an undersize CS'd hole in the MDF, and attached the piece to a length of miter bar to allow easy adjustment of the radius of the cut. A scrap support piece is clamped on the right of the cutter.
A backing block with a matching pivot hole in the center is used to rotate the MDF pieces over the cutter; the block is large enough to cover the cutter when in use. The pieces to be cut are affixed to the backing with double-stick tape.
The stack of finished pieces shown here are the new, replaceable center inserts, to allow for zero-clearance on any size cutters.
Machining the router-mounting plate after the fact to now accept inserts was a bit of work. The polycarbonate material does not take kindly to machining, and the swarf has to be manually removed often; the finished recess and some of the swarf are shown in the photo:
I cut the center out with a nest-of-saws hole saw; it didn't come out on center, but as long as it doesn't interfere with a bit, then OK, else I'll trim it up.
After a bit of brainstorming, I came up with this jig, consisting of a piece of 1/2 inch MDF with a 1/4-20 FH for a pivot, screwed into an undersize CS'd hole in the MDF, and attached the piece to a length of miter bar to allow easy adjustment of the radius of the cut. A scrap support piece is clamped on the right of the cutter.
A backing block with a matching pivot hole in the center is used to rotate the MDF pieces over the cutter; the block is large enough to cover the cutter when in use. The pieces to be cut are affixed to the backing with double-stick tape.
The stack of finished pieces shown here are the new, replaceable center inserts, to allow for zero-clearance on any size cutters.
Machining the router-mounting plate after the fact to now accept inserts was a bit of work. The polycarbonate material does not take kindly to machining, and the swarf has to be manually removed often; the finished recess and some of the swarf are shown in the photo:
I cut the center out with a nest-of-saws hole saw; it didn't come out on center, but as long as it doesn't interfere with a bit, then OK, else I'll trim it up.