Undersized Plywood router bits

[Charles Lent]

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.

[glenn bradley]

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.

A bearing guided bit works fine. Mine runs a template collar. This allows for smaller bits to be used. I generally use a 3/8" spiral. It also gives me a lot of freedom on setting the depth or plunging multiple passes for deeper cuts while maintaining a constant guide/reference surface.

Dado Jig 2.0 (17).jpg

The collar rides against the step, the bit cuts flush to the edge. Since this is a "version 2" jig (meaning I learned something from version 1 ) I built it so that the flush edge can be replaced by gluing on an over-sized strip and re-cutting the "zero clearance" edge. I have done this once already due to an errant cut into that material.

[Curt Harms]

A bearing guided bit works fine. Mine runs a template collar. This allows for smaller bits to be used. I generally use a 3/8" spiral. It also gives me a lot of freedom on setting the depth or plunging multiple passes for deeper cuts while maintaining a constant guide/reference surface.

Dado Jig 2.0 (17).jpg

The collar rides against the step, the bit cuts flush to the edge. Since this is a "version 2" jig (meaning I learned something from version 1 ) I built it so that the flush edge can be replaced by gluing on an over-sized strip and re-cutting the "zero clearance" edge. I have done this once already due to an errant cut into that material.

Makes sense. And who hasn't made v2.0 or v3.0 of an original jig?