With this shop-made base, I turned my rotary tool into a mini router. My favorite application is trimming wood plugs, but I also use it to cut small grooves and rabbets.The base can be made out of any type of lumber.Measure the diameter of your rotary tool and make the inside dimension of the collar about 1/32-in. bigger.
The rotary tool should fit snuggly in this opening, even before you tighten the collar screw. If the fit is a little loose, add a couple of layers of masking tape until you get a snug fit.