Cutting dados in uprights in simple bookshelf

[f95toli]

I am a long time lurker who has  decided to actually post something because I am in need of some help.  

I need to build three bookshelves for our house. "The client" (aka my wife) has asked for something very simple -but well made- that will fit into the alcoves in our sitting room. She has also asked for the shelves to be made from 3/4" BB/BB grade Baltic birch ply with exposed edges (I've used the same type of ply on other projects but with edge banding, but she likes the look of the edges). They need to be sturdy enough to cope with being full of (heavy) books. 

The design we've come up is this

 

Again, very simple. The "uprights" (or whatever you should call them) will be made from 50x25mm (i.e. about 2x1 inch) stained white oak.

Now the problem. To keep it simple I would like to simply do the following

that is the ply is would just be glued into say 15mm  deep dados in the uprights (no fasteners). However, the amount of exposed long grain in the joint is quite small so I am not sure if this will be strong enough. What do you think?

I am also not sure how to cut the dados. Because of lack of space I don't have a table saw (the ply will be cut with my T55), so I am thinking of making a jig and cutting the dados using a router or on the router table. The problem is that I've never had much luck cutting good tight joints this way before, I always end up with small gaps (usually because the ply is somewhat thinner than the diameter of the cutter). Since I will use ply I can also not(?) use an undersized bit and then thin the shelf with a handplane.  

Since I will need to make three shelves and a total of 14 uprights I am prepared to spend quite bit of time making jigs if necessary.

Any ideas or suggestions regarding the project would be very welcome.

Sorry for making my first post so long 

 

  

 

[beantobe]

Nice design! Simple, elegant. Side note- I would be concerned about racking with the type of load you'll be putting on it. Widening the contact at the joint would help a lot. Then it's just an issue of how to transition from the narrow part of the legs to the joint. If you make the transition really subtle I think it would look amazing. But- more work. Just have a template with the curve and use pattern bit on router, table or in hand.

As far as tight joint- use 1/2 inch spiral in router table and have stop and start blocks on fence. Keep router bit height set at depth of notch. You'll move fence incrementally until you're through the whole piece. Clamp backer board on exit and entrance to prevent year out.

[Immortan D]

I like interlocking dadoes better for this type of project.

[Beechwood Chip]

If the client will agree, putting back and side pieces or diagonal bracing on just one shelf will help a lot with racking.

But if the shelves fit into the alcoves without too much clearance, then the alcoves themselves will prevent side to side racking.  In that case I might make the shelves lean back very slightly against the back wall of the alcove, to prevent the shelves from racking forward.

Or, just screw the uprights into the walls.  Simple and very stable.

[Just Bob]

Make an exact with dado jig like this.  http://www.thewoodwhisperer.com/videos/exact-width-dado-jig/

Gang the legs together and cut all of the dados at once.  I would make a prototype shelf unit  to figure out someway to prevent racking. 

 

[wdwerker]

A jig that the upright slides into with 2 guide boards 90 degrees to the upright to run the router along. A smaller bit than the ply thickness lets you fine tune the width. Either use a guide bushing or a bearing pattern bit. If the shelves are going to be spaced equally add a stop to the jig that you can slide a piece of the Baltic into the dado.

i use 2 long thin wedges to hold the part being cut still while cutting. If you make the jig wide enough you could cut several uprights at once.

I used a jig like this in my " Maghgany Library Rolling Staircase" project journal to cut the dados for the stair treads.

A piece of ply for the base, 2 boards the same thickness as the uprights for the next layer, 2 wider boards that the router rides on at 90 degrees to the uprights. Screw everything  together carefully. You might need to adjust the width of the dado and then add a screw to keep it where you adjusted it to. Make test pieces when you mill the stock for the uprights. Sand all of your Baltic and compare the pieces with a pair of calipers ( sheet thickness can vary) before you build the jig. You might try staining and finishing the uprights before you cut the dados. At the area where the bit cuts you need a piece on both sides to prevent blowouts.

[f95toli]

First of all, thanks for all the replies.

@beantobe: That is one of the options I've considered. I do not currently own any spiral bits. How much better are they for dados of this type? I assume you mean an upcut bit?

@Immortan D: I've thought of that and I agree it would be a good idea. But the question is how to make the notches in the ply? The shelves are bit on the wide side for cutting them on the router table . 

@Beechwood chip: Yes, the shelves will be screwed to the wall so racking should hopefully not be an issue.

@Just Bob: I've tried using exact width jigs, but they've never worked that well for me. I suspect part of the problem might have been my old router so I might have another go with my new (well, borrowed) one. 

wdwerker: Thanks for the description. That sounds like the kind of jig that might work

Again, thanks for the replies. 

 

 

[beantobe]

It won't make a dramatic difference if you use a double fluted straight bit. Tear out is usually imminent with a straight bit unless you are meticulous in supported wood at bit exit. I would use a down cut spiral - it will push fibers down into board instead of up and away from board.