Tight Dadoes using A Very Simple Jig

Very simple jig to cut tight dadoes: just a rectangular piece of wood and a metal screw. Photo 1 by Don Tai

Obsessive, I sometimes am, but for getting tight dadoes it is crucial. Without tight dadoes joints are not as strong. I do not have nor cannot justify a dado set, so need to use my single blade. I was going to build a 2 part kerfmaker, when I found this very simple kerfmaker design that uses a single piece of rectangular wood and a screw. Well, I just had to try it. It works exceedingly well, resulting in tight dado joints.

The Jig Design
How simple can you get? A rectangular piece of wood and a metal screw on one end. Brian Grella’s design, video has a cutout on the non-screw end, which allows better clearance of the wood. I opted to not do the cutout. No cutout is fine. My screw is out 2.61mm, for a hand tight fit.

I found a piece of hardwood, which I cut down and sanded smooth. The dimensions were checked with a digital vernier caliper to 1:100th of a mm. I used a #10 1.25″ metal screw with a flat Robertson head. I used a drill press to drill the hole as well as a slight countersink. The screw was so tight as to be difficult to screw into the wood. Small adjustments require effort to turn the screw but will stay tight.

Very simple jig to cut tight dadoes: just a rectangular piece of wood and a metal screw. Photo 1 by Don Tai

How to use the Jig
You’ll need a sled on your table saw. Line up your wood in this order, left to to right:

1. wood to dado
2. wood thickness to insert into the dado
3. jig, opposite of the screw end
4. stop block, clamped.

This cut will be your rightmost cut.

Very simple jig to cut tight dadoes. Rightmost cut: wood to dado, wood that will be inserted into dado, jig (non-screw end), stop block clamped. Photo 6 by Don Tai

Leave the stop block clamped. Remove the wood to insert into the dado. Insert the jig, screw side to the stop block. Begin to nibble away the dado until the wood comes into contact with the jig. This is your leftmost cut. Your dado is now complete.

Very simple jig to cut tight dadoes. Leftmost cut: wood to dado, jig (screw end), stop block clamped. Photo 8 by Don Tai

Adjusting the Jig
If your dado is too tight: tighten the screw.
If the dado is too loose: loosen the screw.
A little movement goes a long way. You will need to make multiple test cuts until you dial in your screw. I needed to do 4 test dadoes before resulting in a hand-tight fit. Once adjusted you need not change it for that specific blade. How tight do you want your dado?

Very simple jig to cut tight dadoes. Dado is hand tight. Photo 2 by Don Tai

Very simple jig to cut tight dadoes. Dado is hand tight. Photo 3 by Don Tai

Very simple jig to cut tight dadoes. Dado is hand tight. Photo 4 by Don Tai

Very simple jig to cut tight dadoes. Inside of dado could be cleaned up with a chisel. Photo 5 by Don Tai

Links:
Jay’s Creations: Shoji screens, using a kerf maker on his table saw, 18″ from the end.

For long and thin wood that overhangs your sled, measure from the end of the sled edge and clamp a stop block on your overhanging wood. Check out the jointmaker pro demo at 13:57

2019 Sep 08 To do a rabbet
To do a rabbet line up your wood so that the saw will just cut a kerf into the wood. Clamp your wood to the sled. Then add the dado width wood and the jig, screw end not being used. Clamp your stop block. This will be your starting point. Unclamp your wood and cut. This is your rightmost cut, one kerf width of a rabbet. Remove the dado width wood and reverse the jig, screw side down. Move the wood next to the jig, for your leftmost cut.

If dadoing a long piece of wood your right sled fence will not be long enough. You can mark the dado on both sides of the dado width, then reverse the wood and continue to do the dado using the sled right side fence.

The Secret to Perfect Dados and Grooves / Woodworking: A different way to do accurate dados. You cut a shim of wood the kerf width of your blade, put the shim against the fence, make a cut, put the width for the dado against the fence, make the cut, then hog out the stuff in between. Instructions for the shim start at 1:33