Quote Originally Posted by Curt Harms View Post
I made a jig like that and use a 1/2 X 1/2 top bearing bit. The bearing runs against the jig's jaws. Set the width of the slot using the piece that's going to fit there, route and perfect fit. The downside is that jig won't cut a dado less than 1/2" wide.
That's the advantage of using the jig style that I posted. The edge of the router base rides on the guide and you can use a smaller bit with no bearing, but your first pass through the jig has to trim the edges of the lower level of the jig to match the distance between the bit and router base. Once that has been completed you are ready to make dados, but you must use that same bit and router every time you use the jig. If making very narrow dados as well as wider you may need to have two versions of the jig, one for narrow dados using a small bit and one for larger dados using a larger bit.

I always write on my jigs to indicate what tool and bit is needed to use with it, so I don't have problems a year or more later when I want to use the jig again. My jigs hang from ceiling hooks in my shop ceiling, so I can find the one that I want quickly, but I'm running out of ceiling space.

Charley.