1-1/2" dado for Bookcase - Woodworking Talk - Woodworkers Forum
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post #1 of 25 Old 03-13-2014, 09:07 PM Thread Starter
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1-1/2" dado for Bookcase

Hello all,

I wanted to be sure I was tackling this project with the right joints and tools in mind. (I started this project under another thread, but this question is specifically about the dado joint). I am building several of these bookcase carcasses and the shelves are double thickness 3/4" maple plywood. I had planned to use a router with a 3/4" profiling bit to cut 1-1/2" dadoes in the bookcase sides, probably 1/4" deep. Back panel will be let in to the sides, glued and nailed.

The outside of the bookcase will be buried in finished construction. Side panels and face frame will cover it.

My question is this: Is a wide dado like this a common joint? Should I be assembling this bookcase differently? My main concern is to make this as sturdy as possible, but I don't want to over-design it unnecessarily. Would biscuits or dowels backed by screws from the outside be easier and equally strong?

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post #2 of 25 Old 03-13-2014, 09:14 PM
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Dados would be my choice.
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post #3 of 25 Old 03-13-2014, 09:32 PM
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Yep, dados

The assembly might be a bit troublesome as they look rather tall, maybe 12 feet high? The dados will have to be very precisely located for them all to match evenly across the whole unit.

The inside verticals will be mated on site I assume and will have to have matching dados on opposite sides of each piece. The 3 units made off site and assembled in place? This is quite a build, but it will be very impressive when completed. Please follow with build and installation photos!

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #4 of 25 Old 03-13-2014, 11:48 PM
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Dadoes are standard joinery for case work like that. It is not difficult to line up all the dadoes, if you can read a tape measure.
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post #5 of 25 Old 03-14-2014, 07:19 PM
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As mentioned they do look to be tall, are you able to get material that long? I would make the dados 3/4" wide and stop one layer of the shelf the depth of the dado on each side. If you leave the sides wide you can dado and then rip to width after or take a batton and temp join then.
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post #6 of 25 Old 03-14-2014, 07:33 PM
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3 stories tall?

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Originally Posted by Keith Mathewson View Post
As mentioned they do look to be tall, are you able to get material that long? I would make the dados 3/4" wide and stop one layer of the shelf the depth of the dado on each side. If you leave the sides wide you can dado and then rip to width after or take a batton and temp join then.
Looks like they have their own footer as well... and it look's like they carry down to the first floor or crawl, but were not drawn as such.
Lottsa weight on those buggers. I agree on staggering the side panels in the dados, but not on adjoining side plates. I wonder if they will be solid wood or plywood on the side plates? Quite a project for sure.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #7 of 25 Old 03-14-2014, 07:34 PM
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Quote:
Originally Posted by mmwood_1 View Post
Dadoes are standard joinery for case work like that. It is not difficult to line up all the dadoes, if you can read a tape measure.
+1. I agree. Clamp both ends together and run the dadoes for each shelf.





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post #8 of 25 Old 03-14-2014, 08:41 PM Thread Starter
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Thank you all for the feedback.

Yes, the bookcase wall is tall. 18' at the short end. The supports between are structural steel with their own footings.

The cases will be built in (6) 8' sections and (3) staggered sections for the bottom where they meet the lowest stair. They are entirely of plywood with fir facing on the verticals and 1/8" steel faces on the horizontals. All that will be seen of these boxes is the inside.

Keith, you said the following: I would make the dados 3/4" wide and stop one layer of the shelf the depth of the dado on each side. If you leave the sides wide you can dado and then rip to width after or take a batton and temp join then.

I interpret this to meen the following: You recommend making 3/4" wide dados for all the shelves, and extending only (1) layer of the (2) layer plywood shelves into the joint. Effectively a rabbeted shoulder joint. Is that correct? What is the advantage here? My only concern is that I would be required greater precision in all of my cross-cutting and gluing. I was even thinking of gluing full 4x8 sheets together with a vacuum press before cutting the shelves.

Additionally, it sounds like I am being encouraged to clamp/batten/secure two shelf sides together and cut a continuous dado across both pieces at once to guarantee alignment. That is a great idea. ripping the sides after cutting dados would be great to avoid blow-outs. I'll have to think about that. I was going to make an elaborate indicating jig on my worktable to align my home-made dado guide.

Thanks for all the input. This whole project has me very nervous, and now there is a big stack of expensive plywood in my shop just waiting for me to make mistakes.

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post #9 of 25 Old 03-14-2014, 08:54 PM Thread Starter
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Here's the rough framing to receive the bookcase boxes (please ignore the temporary guard rail).



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post #10 of 25 Old 03-14-2014, 09:14 PM
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allow me to throw a small wrench ....

Having made several bookshelves/cases with dadoed shelves I have always made the lowest shelves a bit taller for larger books.
Books that won't fit on a "standardized height" won't fit any any of the shelves...so now what do you do? Make them all the same, but tall or have them varied? That's just a question only you or the client can answer.

Another thought is to create a "false dado" by adding a supporting panel and a floating shelf under some of the dadoed shelves. This panel can be whatever height you need which may be determined by the largest books. Another shelf rests on these panels and appears to be dadoed in when corresponding sized panels are placed above them.

So to clarify, you make an extra tall space and then have the floating shelf at what height is needed.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)

Last edited by woodnthings; 03-14-2014 at 09:36 PM.
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post #11 of 25 Old 03-15-2014, 05:48 AM
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you don't need no stinkin' dados....huh?

By using a double side panel wall, the outer or center wall is solid and runs continuous. The "inner" wall is made of precut panels that fit above and below the shelves, cut to what ever spacing is deemed necessary. Each shelf is resting pn the one below, which is resting on a shelf support panel, which is pinned or glued in place....the Erector set of bookcase builds.

For example, if you want a 12" high shelf, you cut 2 identical 12" high by (X) deep panels and build that shelf. Next you may want a 10" high shelf., so you cut 2 10" high panels and build that shelf. All this can be done "in place" and "on site",... no stinkin' dados.... building the shelves up from the bottom. Is it important that they all line up across from right to left...I donno? It wouldn't matter to me personally. The center one could vary if symmetry is important, the right and left being identical.

FWIW.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #12 of 25 Old 03-15-2014, 07:45 AM
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Quote:
Originally Posted by Adair View Post


My only concern is that I would be required greater precision in all of my cross-cutting and gluing. I was even thinking of gluing full 4x8 sheets together with a vacuum press before cutting the shelves.

Additionally, it sounds like I am being encouraged to clamp/batten/secure two shelf sides together and cut a continuous dado across both pieces at once to guarantee alignment. That is a great idea. ripping the sides after cutting dados would be great to avoid blow-outs. I'll have to think about that. I was going to make an elaborate indicating jig on my worktable to align my home-made dado guide.


You might consider just a single layer of " plywood. If there is some reason for the need to do that, like an excessive span, or a visual aspect. Using just " would be structurally fine in most circumstances. You will find difficulty in gluing up full pieces of ". Vacuum bags don't exert sufficient pressure in the centers of large panels, like a veneer press for plywood would.

As for routing accurate dadoes, you can make a jig like this, which is very easy to use, and a fast set up. You might also consider making some shelves to ride on shelf clips, so they can be adjusted up or down if necessary, and allows them to be removed for repair or replacement, and able to flip in case they sag over time.




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post #13 of 25 Old 03-15-2014, 09:58 PM Thread Starter
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Great advice.

I've been wanting to make this exact width dado jig:

http://www.thewoodwhisperer.com/videos/exact-width-dado-jig/

I'm using double thickness 3/4" plywood for the shelves for both appearance and span.

That double wall bookcase idea is brilliant. My shelves will be 16" clear and there is so much space, I'm not going to worry about adjustable shelves. The overall impression of everything lining up is very important to me.

I cut my plywood sides and shelves today. I cut the shelves oversize by 1/2" so that I can glue them and then trim them down on the tablesaw. I gave up on the idea of gluing full sheets or even 8' long shelf blanks. I think it will be too hard to glue and clamp in time. I will just glue up the shelves a couple at a time.



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post #14 of 25 Old 03-16-2014, 12:14 PM
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You know, the great thing about pictures are the little things you pick up on. In the above photo I noticed the use of heavy weights straddling a couple boards to stabilize those roller stands. I have the same stand and more than once it has moved on me while ripping with the TS. I learned to live with the aggravation until just now. A simple and great idea Adair. Sorry not to offer any help on your original question but it's these helpful little things I can't help complimenting on.
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post #15 of 25 Old 03-16-2014, 12:52 PM
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dang roller stands want to tip over

I came up with this idea using the stands minus the rollers and a long straight plank.I needed a level feed table for planing.... or was it jointing, I can't remember, but this was what I came up with:

Remove the rollers and replace them with a 2" x 12" plank on either side of the table.. . To remove the rollers from the stands just push in on the pin, it's spring loaded, and the roller will pop out. Bevel the edge of the plank to avoid the work hanging up on it. The height is easily adjustable on these stands.


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post #16 of 25 Old 03-16-2014, 01:36 PM
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I am building a VERY similar built in bookshelf project starting this week so this thread caught my eye and helped me mentally work through a couple questions I had.

What will you be using to finish the maple ply? I'm actually also using 3/4" ply for my bookshelves. I'll have to post pics of my project as it will be a big undertaking (for me). The only scary thing is that if I get it wrong and don't do a great job, it will not be easy to ignore as it's for my neighbor who lives in the home directly behind mine!! Can't hide them if I wanted to! Time to step up to the plate and hit it out of the park.

I'm tempted to go the non-dado route. If that's the case, how deep can I make the dado in the 3/4" ply before I weaken the ply significantly? Also note that I'd need a dado on both sides and cannot stagger the shelves. One more reason I'm thinking I try to do without dadoes...
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post #17 of 25 Old 03-16-2014, 02:54 PM
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dado vs non-dado?

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I'm tempted to go the non-dado route
.
If that's the case, how deep can I make the dado in the 3/4" ply before I weaken the ply significantly? Also note that I'd need a dado on both sides and cannot stagger the shelves. One more reason I'm thinking I try to do without dadoes...
Which is it?
Non-dado or dado?
Most actual dados in 3/4 " material are 1/4" deep or 1/3 the thickness. So to create a faux dado by adding separate panels, use 1/4" or 3/8" or even 1/2" plywood.

The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
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post #18 of 25 Old 03-16-2014, 04:24 PM
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Quote:
Originally Posted by cabinetman View Post
[COLOR=Blue][COLOR=Black]

.Vacuum bags don't exert sufficient pressure in the centers of large panels, like a veneer press would.

.
Have you tried using undersized plattons for the centers of large pressings?
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post #19 of 25 Old 03-16-2014, 06:27 PM Thread Starter
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I started building a dado guide last night. I chose not to have a stepped guide and just use a 3/4" profile bit since the dado is large and I have a lot of material to hog out. I glued black locust edge banding on the plywood pieces for longevity. I don't have a joiner, so I did my best to get the edges straight and square with my hand power planer. I'm looking forward to finishing this and giving it a run. I made it long enough to cut across two side panels.


Last edited by Adair; 03-16-2014 at 06:46 PM.
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post #20 of 25 Old 03-22-2014, 12:13 AM Thread Starter
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I made a little more progress today. I was given a radial arm saw because I had no means to make cross-cuts. Built a quick table for it from melamine and squared it all up. I cut all the shelving stock 1/2" oversize and glued up one test shelf using a couple anvils instead of clamps. Then I tested out my dado jig and made my first ever dado joint. This is fun stuff! I think the 1-1/2 dado looks stout and sensible. The only problem is I think each dado joint will be specific to the corresponding shelf since there is a fair amount of disparity in the plywood thickness.





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