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Dado Jig for Plunge Router

29827 Views 35 Replies 16 Participants Last post by  Timberwerkz
Dado Jig

We have all seen many jigs to put in a dado for shelft(s) in a book case or cabinets.

Most have two boards that hold the router in place,from moving from side to side, like the one Norm made on his show most will jam when you push the router up the tack .
This one will Not jam because in runs on the brass guide that is true unlike most base plates on the router base.
They stamp out the base plate and it's not a true machined part.
This jig will take that error out and you will get a true slot,right on the button every time.
You can make a quick guide to use with this jig with 1/2" MDF and a dado slot and 3/4" plywood cut off stock to hold the spacer guide from one slot to the other.
In that way you will get a slot every 12" or what every you want it to be.

We all know that plywood is not a true size that's to say that 3/4" plywood is 23/32" and we need to use the right bit size to get it to fit right,same with 1/2" and 1/4" plywood.

I try and make most of the book cases or cabinets 11 3/4" wide so I can put the slot in both at the same time and then split the 24" plywood and end up with both sides that are dead on.
Then use a face frame to cover the plywood ends and to hold the shelf sq. and add support to the shelf ,with a T & G bits you can put a slot in the shelf and the face frame.
T & G bits ,set it to cut 1/4" deep on all slots.
You can also use the T & G bits to make a 1/4" spline that's 7/16" wide and it's dead on 1/4" thick and it will work great to hold the shelf and face frame as one.

I have put a link or two for the bits you need to use and the bits you need to make the jig and the brass guide, It true that Harbor Freight has a better price on the brass guide set, but it will not come with the 1" O.D. one you need to use for 3/4" plywood and this jig. for the bits and brass guide kit.

Plywood bits H5559 and H5558 at a good price
1" bit 1/2" shank C1017 also a good price
Brass Guide Set H3134 it's bit high in price BUT has the 1" guide you need.

If you need more info please ask :)

Plus some other snapshots of jigs, see below ▼
NOTE*** drawing below/plans

Bj :)

Snapshots are out of order sorry about that, out of my control.


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Bob, I like this jig a lot. That is as long as the plywood bit that's being used is truly the same thickness as the plywood that is actually going into the slot. Is it your experience that veneer ply is truly 23/32? or is it even thinner-like 22/32?

I just bought a couple plywood sized bits at Rockler this week. I used a 23/32 to cut a dado using a 1 runner sled with my router table and was using some secure hold downs to prevent the stock from sliding around. I found the dado joint was too loose when I slid the stock into the dado. When I measured the thickness of the plywood I found it was 22/32 instead of 23/32 and that 1/32 is a lot when building something. The ply I bought was oak veneer plywood that I got at my local Home Depot.
Hi Paul
The plywood is going the way of the candy bar getting smaller and smaller if they can save 1/32 of stock when they make the plywood they can many more and still charge the the same price.
At some point they will need to tell you and I that the stock is unsize that's to say it's not 3/4" it's not 23/32" but now it's 22/32" and next week it maybe 21/32" I see no end to this.
Just as a side note, they are building some new homes down the road and I stopped by to just have a look see, the roofing plywood was marked 5/8" chip board but it looked like 1/2" T & G to me and when the roofer was putting on the roof it bent like 1/2 " on 16" centers when he walked on it.
And the new homes are 450,000.oo not cheap homes.
I recall when a 2 x 4 was a 2 x 4 but now days....well ,the way of the 5 cents candy bar.
And I think that's why the MDF and the WoodStalk will take over the plywood sales.
For one thing when you and I buy 3/4" MDF it's 3/4". :)
And when you and I buy 3/4" WoodStalk straw veneer it's 3/4" so you may want to stay away from veneer plywood.

Bj :)
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With the unpredictability of the stock in mind, it would be slick to still use a bushing as the guide for cutting slots but incorporate a width adjustment somehow. If one could lock the jig for the width of the stock and then cut the slot running the bushing against the edge one way and against the other edge on the way back it would still be an improvement over the trapped base jig idea
Hi Paul
You can use a 5/8" router bit (or a 1/2" one if you don't have a 5/8" bit) and just move the jig over just a bit and reclamp it down.
This is what I would do to fix this type of error, make the 1st 5/8" slot then clamp a setup block down, then unclamp the jig and put a metal ruler (on it's side) that's about 1/32" thick, right next (in front) of the setup block then reclamp the jig down and make the 2nd pass.

Bj :)
I don't know if this is of any use to you but I found the plan on the internet a few years ago. All you have to do is place a piece of the shelf material in between the straight edges and clamp it up and then rout out the correct size Dado everytime. Here is a pic of it:


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I read in the newspaper that Dow is no longer making the building material that was being used on the RouterWorkshop. (Wheatstalk ? I don't remember)


Jerry, one of the moderators here said he lives close to that mill and they are discontinuing that product. You were correct- it was fibre made form wheat. -Derek
Woodstalk was an excellent idea ahead of it's time. I have a feeling it will return in the future. At this time it is not a profitable item for Dow. Let's all hope it returns soon.
That jig idea but using a rub collar as opposed to bumping the base against fence walls would lock in the exact thickness of various widths of stock.
Paul, the router base IS the guide bushing with this jig. It's dimensions do not change. This jig will also allow you to accurately cut a board to thickness like with a planer. It just takes a lot longer.
Where are you finding the 1/2" MDF. I 'm in No. Calif. Within 20 miles of Lowes, Home Depot, and several lumber yards. All I find is 5/8 or 3/4.

Thanks, Rusty

I got my brass template guides yesterday from Pricecutter(including a 1" O.D.). Right away I built a modified version of your dado jig. I modified it because I dont have a 1" bit or 1/2" MDF. So I cut down 2 planks of left over laminate flooring using 1/2" plywood on the ends and the new 1" guide for the spacing. Works great. I,ve allready used it to route a stopped dado in the surface of my new table. So I could add T-track(not miter track) for feather boards or whatever else I may need. Would post pics but I'm having trouble with my camera.

Thanks Rusty
18243015 said:
Where are you finding the 1/2" MDF. I 'm in No. Calif. Within 20 miles of Lowes, Home Depot, and several lumber yards. All I find is 5/8 or 3/4.

Thanks, Rusty
I found it at my local HD on the east coast but only in 2x4' sheets, not 4x8. This is better for me as it is easier to transport. They also have 1/4" mdf.

Hi Rusty

I also get the MDF stock from H.D. like Michael, in comes in 1/8",1/4",1/2",5/8",3/4",1" and with luck 1 1/4" but it's hard to get the full 4' x 8' in the all sizes, like Michael I look in the precut bin for what I want or need I also get it from a sign supply company they carrier the full 4 x 8 in stock for sign painters, it's a bit higher in price but it's 4 x 8 when I need to use a full one.
I like the MDF stock it can be used in so many ways because you don't need to worry about the grain directions and you and I can used it all up for so many projects unlike the normal wood boards we get from trees.

Like you I have started to use laminate flooring in some of my projects it's flat ,it comes prefinished,and strong for it's size, and smoooooooth :) .

Brass Guides, I got the bug from Bob and Rick (RWS) when I saw all the items they made using brasss guides and templets , it's easy to make one of anything but to make a pair or make two or more of the same that's the hard part when it comes to using the router or any other machine but the brass guides take care of that one easy.

Tally , just made some fishing lures that blew me away with some help of the members of this fourm he did a great job using the brass guides and a jig, I didn't think you could do that with router but it just goes to show you and I how versatile the router is when we use the guides.

Have a great weekend
Bj :)
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Rusty, go to a local plywood wholesale house. They will have the 1/2" MDF however they will not sell it directly to you but get them to call one of their dealers close by so they will sell it to them and you pay the dealer. In most cases that I have found they will go ahead and make the deal there.
Regarding 3/4" plywood being thinner, the world has gone metric and plywood imported from other countries comes in 6, 9, 12, 15 & 18mm each of which is thinner than 1/4", 3/8", 1/2", 5/8" & 3/4"
3/4" is 19.05mm so the plywood is 1.05mm thinner, approx 40thou.
UK started with metric 35 years ago but many still prefer imperial measurements.
Very few 30 year olds have ever known inches as all they were taught at school was metric.
Because most routers still come with 1/4" or 1/2" collets we can use bits made for inch as well as metric.
To cut dados for 18mm sheet material I have an 18mm cutter.
It can often be confusing having both metric and inch sizes but I often find it helpfull such as when cutting a 1/2" mortice and starting with a 12mm bit then cut to finish size with a 1/2" (12.7mm) cutter.
Here are some Dado Jigs that will accommodate any thickness of sheet stock & make doing dados a snap.
One is a manufactured jig from WoodLine USA called the DadoWiz & two you can make your self from ShopNotes & WoodSmith magazine.


Heavy-Duty Adjustable Dado Jig Woodworking Plan

The best one is in ShopNotes issue 76

You can check out a video of this jig in action with this link.
Look near the bottom of the page

Hope these help

I just bought the DadoWiz but have not used it yet but it was featured in a wood magazine a few months back not sure witch one at this point but may be able to find it if some one needed to see the article.

I still plan to make the one in ShopNotes issue 76

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Those plans look prety good. But they both trap the routers sub base which is not allways true. BJ's jig has a 1" wide slot to accept a 1" template guide. All you do is center the jig over the center of the needed dado. If you need it wider than the largest bit that fits thru the guide just move it over and reclamp after the first pass.

It's quick and easy to build. And I have used it several times since builing it.

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