# Dado joint question



## JumpingJeff (Jun 8, 2009)

Hello there,
As a relative woodworking newbie I have a question about Dado joints. I am making a bookcase (is everyone's first project a book case? It sure seems that way.) with the shelves attached with Dados. How tight should the Dado joints be? Should I use some significant force to get them in, or should the slip in easily?

Do you think the Dado joint alone (with glue) is strong enough, or should I use a couple of finish nails in each shelf as well?

Thanks for your help.
Jeff


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## kerflesss (Mar 7, 2009)

A dado should be a nice snug fit and glue should be enough to be secure them. I would suggest that before fitting them that you do all your sanding of your shelves so that your fit be right otherwise they will not be snug. Norm does toe nail dado joints with brads in places you wont see them (make sure you use a square) such as under shelves but it depends on your design. I do toe nail on larger projects more for assembly ease to hold pieces in place while man handling opposing parts… it can be a hand full.


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## JumpingJeff (Jun 8, 2009)

Thanks Kerfless.
The shelves do not seem that large at 23" in length so I will skip the brad nails. Thanks for the tip about sanding before test fitting. While I had planned to sand the shelves before glueing them up, I would have already fit tested and cut the dados. Thanks for saving me from that misstep.

Jeff


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## Kindlingmaker (Sep 29, 2008)

...after sanding EVERYTHING on the inside mask on both sides of your dados and the shelves because the glue can get real messy real quick! Pull the masking tape off after wiping off some of the excess glue after about 15 minutes. A glue joint is stronger (should be) than the wood itself. My outside garden gates are completely glued together, no metal at all, and they are as strong as the day they were made 2 years ago.


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## Newton (Jun 29, 2008)

Jeff,

Not to throw a wrench in the works but are you going to stop-dado the sides of the bookcase so the dados do not show in the front? Unless, of course, you want to see the dados? Before asking the question I should have asked whether you are using a router or dado set on the table saw?


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## JumpingJeff (Jun 8, 2009)

Hi Don,
I'm undecided on using a stop dado. I was thinking of stopping the dado 3\4" from the front of the shelf, and then trim the shelf so it fits in that front 3\4" without a dado. However, since everything is plywood, and will be faced with maple, is there a point in using a stopped dado? No one would see the front edge anyway.
I am making the dados with an 8" dado set on a radial arm saw.

Thanks for the masking tip Kindlingmaker. That will save me a lot of cleanup time with the glue.

Jeff


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## sbryan55 (Dec 8, 2007)

Jeff, if you are going to put a face frame on the bookcase, then there is no need to do a stopped dado. You are correct in that the front edge will not be seen.


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## Newton (Jun 29, 2008)

Jeff,

It is easier to put the solid edge on the shelves before you assemble the case, that way you can sand the edge flush with the shelves and even finish the unit before assembly.You can still through dado the sides, glue the edges on and sand flush. the edgeband doesn't need to be thicker than 1/4" and can be put on with wood glue, no nails. Use painters tape to hold the edgebanding on while the glue dries. Good luck….Post pictures!


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## JumpingJeff (Jun 8, 2009)

Thanks for all the tips. I have one more end piece to sand, and then I will be cutting the dados.

Jeff


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## JumpingJeff (Jun 8, 2009)

Okay, so I cut my first Dado joints the other night. They didn't come out quite as planned. The middle of the bookcase is two pieces of birch ply glued together. I have a bunch of bisuits (8 of 10) to help hold it together. The problem is the Dados on one side are about 1\16" off from the other side, so the left and right shelves will be at different heights. 
I was thinking of widening the dados so that the bottom edges line up on both sides. If I do this, what can I shim or fill in the top edge of the dado with since it will be too wide, or should I just accept that the left and right shelves will be at different heights. I know realize I should have raised the blade and slid it all the way down to double check that my cut lines would be the same on both sides.


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## RedShirt013 (May 17, 2008)

Might be easier to run some birch strips the size of your dado and glue them in, sand flush, then recut the dados. For each shelf then cut both sides of the middle pieces plus the gables the same time with the same setting. Hide the "ugly" side of the dado cut on the side blocked by the shelves and not visible at eye level.


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## Newton (Jun 29, 2008)

Jeff,

I really don't understand how they are not at the same location. I take it that the 2 pieces were a divider. Were the 2 pieces glued together before you dadoed? If so, I don't understand the biscuit part. Did you use a router or a dado set in a table saw? A lot of times, if the sides are not too deep, I will dado then rip to get my sides. Help me understand the problem and I'll try to help. Chances are I've made the same error!


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## JumpingJeff (Jun 8, 2009)

Hi Don,
The dados were done using a dado set on a radial arm saw. 
I understand what you are saying about making the dado first and then ripping the sides. That would have made more sense, and cut down on the chances for error.
Jeff

The 2 pieces form a divider in the middle. They faces are glued together. I didn't think just gluing them would be strong enough, so I added in some biscuits. The biscuits may have been overkill. The pieces were glued up before I cut the dados.


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## JumpingJeff (Jun 8, 2009)

Hi Ed,

I'll have to think about cutting strips to fill in the existing dados. I think I would cut them out of something other then the birch ply. That would avoid having the ply show. I have some scraps of maple I will think about using. Luckily I will only have to do the 2 dados on the one side. The middle shelf I had decided to make adjustable.

Thanks for the tip.
Jeff


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## Newton (Jun 29, 2008)

Jeff,

I can't imagine how the dadoes are at different locations. I had a similar thing happen and found that the dadoes were not square to the edge. If the saw is 1/32" out of square it multiplies itself because you are indexing off of each edge. It may be hard to explain but check the dadoes and see if they are square to the edge. Be accurate as it only takes a little!


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## JumpingJeff (Jun 8, 2009)

Hi Don,

I know what you mean about the blade being square to the fence, and the table. I spent hours getting that part setup.

I think the dados are off because my start line was a little bit off or I lined the cut up a little bit off.
I will check to make sure the dados are square to the edge though. Since I used the same edge for both cuts, I would think even if the edge wasn't square to the dado, both dados would line up, but my shelf would have a noticable slant.

Jeff


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## JumpingJeff (Jun 8, 2009)

If the saw wasn't square, wouldn't the start of the dado cut line up, and then as you got to the end the cut would be off since the saw would travel left or right down the track depending on which way it wasn't square? I used the same edge to start the cut on both sides. I think I just lined it up wrong when I cut the reverse side. 
The top and bottom shelves on the left side are both off 1\16" from the top and bottom shelves on the right side. 
The face frame is the exact width of the two 3\4" pieces of plywood that are glued together. 
It is too late to start working now, so I will give it some thought on what I want to do. My original thought was to cut the dado a little wider, and then fill the gap with something. I was worried that would not make a strong joint though. I think cutting a new faceframe piece 1\2" wider to get the 1\4" overlap on either side wouldn't be that difficult.

Jeff


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