I have made for me a simple jig to making perfect circles with my router. I can make circles with radius from about 15mm to 500mm. It is very usefull tool for me. I can make pokes for tea candles or coffe table with it.
Step 1: Measuring and planning
At the first we nned to know the distance between the guide rods and the distance from working surface.
Step 2: Drilling
Diameter of rods in my case is 8 mm. Now we are able to drill the holes for guide rods. I decided to use aluminium rod of rectangle shape 10 x 20 mm. 2 holes for guide rods, 3 holes to join with base plate. The guide rods need to be drilled at the ends and make a threads. I have made it with my lathe.
Step 3: Base plate
For base plate I choose the 8mm thick Makrolon polycarbonate plate cause of visibility, nonbreaking. In the base plate I have routed long hole to have possibility to use any bit from my bank of router bits. Now we can assembly all this stuff together and can make some nice and accurate holes, circles we need.