Auto-Width Dado Jig Version 2

This jig had appeared in use or in the background of a pic during another thread. Lee Schierer asked to post more about it so, here we go. This is based on the version in ShopNotes #76. the primary difference being that I use an 'edge guide' clamp instead of their threaded rod solution for clamping the jig to the material to be cut.

Another modification I made to my dado jigs back in 2006 was to add a rabbet on the reference edge. This allows the router to reference via a template as opposed to via the outer edge of the router plate. This makes router orientation a non-issue (assuming you've centered your template collar and plate) and makes the jig smaller and therefor lighter.

I use featherboards and the router table to cut the large rabbet that will accept the edge-guide-clamp.

Attachment 378612 . Attachment 378611

The cross arms are your fence and so must be true. I glue them, dialing them in for 90* and then clamping. Once the glue is set I add screws for strength.

Attachment 378614

I had to grind a bit off of the flat head 1/4-20 screws I will use to attach (and adjust) the clamp. your screws or bolts will depend on your choice of edge-guide-clamp.

Attachment 378613

Let's call the part of the jig that the clamp is on the 'small jaw'. What doesn't show well here is the slots that allow the 'large jaw' to adjust. I will add that pic in the next post. At any rate, you end up here. The edge guide is positioned so that when its moving jaw is fully engaged, it is even with the jigs near-end cross arm. This near-end cross arm is your reference edge against your material to square the jig. So, slide the cross arm up against the edge of your material, slide the jig over so that the slot is dead-on your desired dado location and lock the clamp.

Attachment 378615

Like other such jigs, the width is set "auto-magically" by clamping the material that will go into the dado between the jaws. This is done prior to positioning the jig on the material to be cut.

Attachment 378616

Here is a picture showing the underside prior to my removing some unneeded material from the large jaw in order to further reduce weight.

Attachment 378618

And here is the unit in use. You can see the large jaw is now not quite so large due to the removed material.

Attachment 378617

cont'd

Here is a pic of the adjustment slots that are on the large jaw. Ignore what I am pointing at, look at the slot :).

Attachment 378621

Here is a better shot of the rabbet that accepts the PC template collar. Now you can look at what I'm pointing at :).

Attachment 378620

I use a 1/2" collar and a 3/8" spiral bit for most things. The 3/8" bit is smaller than most things I use this jig for. This allows the template collar riding the jaws to cut an exact match to the material gripped between the jaws when you are setting the width.

Attachment 378622

I made mine to cut dados from under 1/4" through 3" (the width of my ZCI's in my tablesaw sleds). That's pretty much it.