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.

[Cliff Rohrabacher]

Nice jig. Somebody please tell me why they use a router for dados?

I know why I do it and it's only in limited circumstance where setting the dado blade is going to be a hassle or inconvienent because I'm only going to cut a couple of slots or the rare event that I absolutely have to maintain my saw set up while also making slots.

So, educate me, please.

[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.

[Billy Chambless]

Nice jig. Somebody please tell me why they use a router for dados?

I can tell you my reason: the absense of table and RA saw. (I was recently delighted to learn this is called "Euro Shop" now; I used to call it "poverty".)

Some would argue that a router is safer than a dado head in a saw.
Depending on the size and shape of the stock being dadoes, a router might be easier. For a small production run, I was thinking about a non-adjustable, multi-dado version of Glenn's jig for dadoing bookcase sides. That strikes me as faster and perhaps more accurate than saw methods.

But honestly, the real reason is that some of us just have a fetish for teaching routers new tricks.

[glenn bradley]

Cliff, for me its money right now. I plan to buy a real dado set but something else keeps eating up the dado fund. Even once I have a good set there are some cuts where it is easier to bring the tool to the work rather than vice versa. Long narrow pieces like bookshelf sides are easier for me to route than to cross cut on the TS but, I'm just a little guy.

[John Schreiber]

Glenn,

That "rabbet shelf" is genius. I wish I'd seen this before I built my jig. I think I can modify mine to work that way.

Thanks for the idea.

[Rob Bodenschatz]

I built one that is very similar to Glenns. I do have a good dado set (Freud SD508) but there are certain scenarios where the router is quicker, more accurate & safer. One is where I needed to dado across a seven foot long board. Rather than try to manuever it over the table saw, it was easier to plop that jig on it and rout away.

[jonathan snyder]

Thanks Glenn,

Now I have to build yet another jig! That is a great idea, and much better than my current dado jig. This is quite timely, as I am building a auxiliary table for my drill press, and plane to cut dado's tomorrow AM for the t-track. I think I'll whip together a new dado jig first.

Thanks again
Jonathan

[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?

[Laurie Brown]

I can tell you my reason: the absense of table and RA saw. (I was recently delighted to learn this is called "Euro Shop" now; I used to call it "poverty".)

But honestly, the real reason is that some of us just have a fetish for teaching routers new tricks.

Hey, I have one of those "Euro Shops" too! Glad to know there's a nicer name for it now.

In my case, I don't have a dado blade set for my saw, so the router is my only option. I don't use dadoes a whole lot, though, so I've only used it for that twice.