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.

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

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

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

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

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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.

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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.

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

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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.

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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.

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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.

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

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Then I make the cut.

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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.

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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.

[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.

[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

[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.

[Paul Greathouse]

Thank You Glenn,

You just saved me over $300. I was seriously considering the Woodhaven dado jig for $284.99 plus $31.66 shipping. I wanted something to produce tight fitting dados without a lot of setup fuss.

I did make an improvement to Glenn's jig that some of you might be interested in. I added a piece of Hartville T-Track and a clamp to the bottom of the jig to prevent having to clamp from the top.

Heres a couple pictures.

The first picture is of the jig upside down showing the track and clamp.
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This is of the top side.
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This jig produces super accurate and tight dado's. I am in the process of building a tall pantry with the swing-out shelves for our new kitchen cabinet build. This jig will speed up the process of dadoing the 48 or so shelves that will be in the pantry, along with all the dados on the rest of the base cabinets (I've already got the top boxes built).

[glenn bradley]

Cool modification Paul. Clamping can be a little clumsy at times on this thing. I just happen to have some track right here handy . . . thanks right back at you.

[Dan Chouinard]

What is the preferred bit to use with this jig? The only ones I can find are 1/4" shank.

[glenn bradley]

I use a 3/8" upcut solid carbide spiral bit as I usually don't make dados smaller than 3/8" with this jig and I can make up to 3/4" dados easily, larger with a bit more effort. My favorite is a Whiteside RU4900.

[Tom Ewell]

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.

I'll add a little more to this old thread.

The variable dado jig and router is a little more versatile to setup, like you say for infrequent jobs or small quickies.

I used a similar jig (with a pattern bit) to plow out blind angled dados on dress carriages to accomodate the treads for an open riser staircase, a little tough to do on a TS or RAS.
As the OP pointed out, if there is some variation in stock thickness, the jig accounts for that.

[Carl Beckett]

Glenn,

Great writeup! Some years ago I made an essentially identical jig as this, and have found its my 'go to' jig for quick, tight dado's. I use a straight upcut bit with a bushing guide in the router base. Its foolproof!

You will get many years of satisfying use out of this one! (the more satisfying designs are the ones that are still satisfying after 100 uses......)

For those of you considering it, go for it! (you will appreciate!)

[Dan Chouinard]

I have never used a spiral bit. What are the advantages of these bits when making dado's and how do you choose between upcut or downcut?

[glenn bradley]

(the more satisfying designs are the ones that are still satisfying after 100 uses......)

Several folks on here have made this jig over the years. My first crude one is still going strong. I used it just last week.


I have never used a spiral bit. What are the advantages of these bits when making dado's and how do you choose between upcut or downcut?

Generally a cleaner cut for a longer period of time. A brand new straight or shear bit will cut beautifully. I have spirals that I use more often that have outlasted straight bits by quite a margin. It doesn't take many inexpensive duplicates to make a quality spiral pay for itself pretty quick. Top quality straight bits will take a few sharpenings which increases their value but, sharpenings change diameters and therefor they cannot continue to be used with this type of jig. The offset for the template guide expects a certain bit diameter to be accurate.

This jig clamps firmly to the surface being cut and provides a bit of a zero clearance effect to minimize tearout so I use an upcut. For veneered surfaces of really tearout prone material like red oak or ash a downcut is often preferred. Care must be taken to keep the dao and the flutes clear of spoil or you can get burning. The upcut is a little like a drill bit. It pulls the spoil out of the dado as you go (dust collection recommended, as always).

Most importantly, we all have our own favorite way of doing things based on what we do. Go with what works best for you.

[Dan Chouinard]

Thank you Glen for this jig that I will make asap. I will be using it to make dado's in plywood for cabinet assembly. Is upcut the way to go and who makes good spiral bits?

[Jerome Hanby]

Since god alone only knows what the actual thickness of a piece of plywood is going to be, a router based adjustable jig lets you use the plywood itself to set the width so you get a nice tight dado. Also for long pieces (I'm thinking book shelf sides). It's much easier to move the router and jig over the secured piece than it is to try to line it up and feed it over a dado blade on the table saw. If you have a RAS with enough travel and getting the width set properly is not an issue, I'd use the RAS and a dado blade, especially if I had a ton of parts to mill. One other thing the router and jig gives you, again thinking of a bookshelf, you can line up the sides, clamp the jig across both, and cut matching dadoes. I guess if your RAS had enough travel you could do the same with it, but mine would only handle a very shallow book shelf if I wanted to cut both sides at once...


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.

[Jerome Hanby]

Top quality straight bits will take a few sharpenings which increases their value but, sharpenings change diameters and therefor they cannot continue to be used with this type of jig. The offset for the template guide expects a certain bit diameter to be accurate.



When I rebuild my dado jig (It's the Shopnotes version with the clamp built in and hardboard guides), I'm going to make the hardboard pieces attach with screws instead of glue so that they can be replaced. That way if the bit diameter changes (or I decide another bit is better) then I can replace the hardboard, make a quick router pass on each side and be back in business.

[glenn bradley]

Thank you Glen for this jig that I will make asap. I will be using it to make dado's in plywood for cabinet assembly. Is upcut the way to go and who makes good spiral bits?

I like the Whiteside RU4900. As Jerome mentions, this jig uses your material to set the width so irregular thicknesses are no problem.


When I rebuild my dado jig (It's the Shopnotes version with the clamp built in and hardboard guides), I'm going to make the hardboard pieces attach with screws instead of glue so that they can be replaced. That way if the bit diameter changes (or I decide another bit is better) then I can replace the hardboard, make a quick router pass on each side and be back in business.

Cool feature Jerome.

[Dan Chouinard]

Glen, I bought the RU4900. What kind of collar is appropriate to use this bit with your jig?
Thanks

[glenn bradley]

I am not home right now but will be able to check after work tomorrow. I use one that I believe has 12/32" ID and I am not sure on the OD but, it's tight. Any close fit collar will do as on my version the rabbet is cut over-deep and then a pass with the router, collar and bit set the final dimension of the rail. I now use standard brass Porter Cable style collars but, the principle is as in the pic earlier in the thread.

http://www.sawmillcreek.org/attachment.php?attachmentid=50773&d=1164254928