Auto Adjust Router Dado Jig - Pics

[glenn bradley]

While making a new cabinet for my router table I needed to make some dados. I reluctantly took my poor quality dado blade out and made a cut. As usual it was poor; I usually make my dados with the router table but, it is all apart as you might expect.

I have used quickie jigs of this sort for hand routed dados but, decided to make one a little more permenant. Thought I'd share the build here:

The concept of the jig has different versions. For any version you want some flat stable lumber. I had an old maple table top that was part of my parents newlywed furniture 50-odd years ago. It had picked up some water damage while making it's travels from one of my dad's garages to the other over the years. I ended up with it and it has been waiting for a second life.

The jig requires two guide rails to control the width of the cut and two end rails to support the guide rails.

wood cuts.jpg

The general layout allows the guide rails to open and close for different widths of dados

general layout.jpg

Over to the drill press to drill some starter holes for the adjustment slots.

starter holes.jpg

On the narrow guide rail I also need a hole for the carrige bolt and a recess for the head of the bolt.

recess holes.jpg

As my router table is down I used the old standby to cut the slots.

slots.jpg

Here comes Part 2.

[glenn bradley]

To allow the router bit collar to ride along the guide I cut some rabbets. I make the cut deep enough so that in a later step the collar will ride in the rabbet and the bit will cut the extending shelf of the rabbet to size.

rabbets.jpg

coller.jpg

Here's a shot of trimming the rabbet 'shelf' to create a sort of zero clearance reference edge on the guides. I now know using this guide and bit, the cut will be right on that edge.

coller and bit.jpg

With that done I can attach the side rails permanently to the wide guide rail.

attach rails.jpg

With the side rails attached I add the carriage bolts, fender washers and some knobs for the narrow guide rail which moves to set the dado width.

knobs and washers.jpg

Part 3 coming up.

[glenn bradley]

Now using the slots in the side rails and the carriage bolts and knobs, I can size the dado width using the actual material that will occupy the dado.

set jig width.jpg

Now I can clamp the jig to the material to be cut using the zero clearance reference edge of either of the guide rails to line up to marks I've made to indicate where the dado is to go.

jig to material.jpg

I know the thickness of the guide rails and add this to the depth of cut I want to make.

set depth.jpg

Then I make the cut.

cut dado.jpg

Now even if my BB ply ends up being a different thickness by as much as 1/64" between to panels (like the last two panels I just bought), I can still make a nice tight dado no matter which panel the board comes from.

perfect fit.jpg

Glenn ;-)

[Walt Caza]

Hi Glenn,
All hail the master of homemade shop jigs !
As usual, this setup looks super-useful and your post really explains everything in a way to be useful to others.
I want to share that because of Glenn's jig posting influence, I have purchased a drafting triangle (his suggestion, and a good one) for my own
shop. It helped me build a crosscut sled with great accuracy, and stays
square even if you should drop it...
Thanks for sharing pics,
Walt

[Billy Chambless]

Glenn,

Great post! I was thinking of doing something similar, but your approach is cleaner and simpler than what I had in mind. Thanks for sharing this.

[glenn bradley]

Billy, If the other method you mention involves using the edge of the router base against the guide, I have had success there too. It is important though to have a quality base that is as close to perfectly round and centered on the bit as possible. Even with the bushing collar version in my post I run the same spot on the collar along the guide in both directions.

I should have mentioned that in my post; left to right just as if you were profiling an edge for the first pass. rotate the router 180* and right to left of the second pass. This little extra effort will assure no deviations in the dado side-wall.

[Jim Becker]

Excellent pictorial! Thanks!

[Allen Bookout]

Hey Glenn,

I built your adjustable dado jig last night and am using it today. That is a neat set up and so easy to use. Thanks!!! Allen

PS The check is in the mail.

The first picture is of the jig and the second one is using the jig with stops.

[David Rose]

Allen,

If you made one cross leg of the jig square to the guide (cut) line, you can butt that cross member to your work edge for a 90 degree dado/groove. That takes one more step out of using it.

David

Hey Glenn,

I built your adjustable dado jig last night and am using it today. That is a neat set up and so easy to use. Thanks!!! Allen

PS The check is in the mail.

The first picture is of the jig and the second one is using the jig with stops.

[Allen Bookout]

Glenn, I am glad that you posted that picture of the debth gage as I had seen reference to building one but had not seen plans. I saved the image for a later project.

Allen,

If you made one cross leg of the jig square to the guide (cut) line, you can butt that cross member to your work edge for a 90 degree dado/groove. That takes one more step out of using it.

David

David, Actually I made both cross legs exactly 90 degrees to the main long piece so that I could do that from either end. The reason that I did not have it slid up against the workpiece is that I had equal cuts for box joints down from the top of all four pieces so I knew exactly where I wanted to place the jig to get the dados to come out right at the corners. I was making a box that needed an interior shelf supported by all four vertical pieces due to load. It is kind of hard to see from the picture as the one that I was working on attached to a front piece that did not extend to the bottom. You may not know what I am trying to say as my explanation is about as clear as mud but I know what you are saying. Thanks!

[David Rose]

Nope! I know exactly what you "were trying to say". You said it well. I had a suspicion that you had a reason. Just wasn't sure.

David

Glenn, I am glad that you posted that picture of the debth gage as I had seen reference to building one but had not seen plans. I saved the image for a later project.


David, Actually I made both cross legs exactly 90 degrees to the main long piece so that I could do that from either end. The reason that I did not have it slid up against the workpiece is that I had equal cuts for box joints down from the top of all four pieces so I knew exactly where I wanted to place the jig to get the dados to come out right at the corners. I was making a box that needed an interior shelf supported by all four vertical pieces due to load. It is kind of hard to see from the picture as the one that I was working on attached to a front piece that did not extend to the bottom. You may not know what I am trying to say as my explanation is about as clear as mud but I know what you are saying. Thanks!

[glenn bradley]

Very cool, Allen. I'm glad to see someone benefit from a post after I have benefited from so many other's posts.

[Peter Stahl]

Glenn,

Nice looking jig, I like the rabbit for the collar. Can you tell me where you got the cen tech thingy for your depth gauge? How is it held in the depth gauge?

thanks, Pete

[patrick anderson]

Thats a nice jig mate, I think I'm going to have to have a go at one.

Mods, would it be possible to have a section of the forum for jigs, so a great idea like this can be quickly accessed?

[glenn bradley]

Peter,

Centech on sale at Harbor Freight, $6. I traced around the Cen Tech (which is a plastic digital caliper with the head cut off) and routed it out. Glued in with spots of silicon rubber so it could be pried out if require. Battery changes without removing it. You may want to use spots of latex chalk as I have learned (here at the Creek, where else) that silicon present in the shop can have effects on finishes. There is a better shot of it here:

http://www.sawmillcreek.org/showthread.php?t=46039