Making stackable shelf boxes

I needed more shelf space in a bedroom. Rather than build more shelves, I took the books off my bookshelf and piled them behind the couch, where I used to have this shelf. So I figured I should build some actual bookshelves for behind the couch instead.

I used all recycled material, some old Ikea shelves, and some varnished pieces of wood from a dresser that I picked up off the curb. (Whenever I see thrown out furniture made from good materials, I take it apart for reuse.)

The Ikea shelves have a strip of metal along the end grain edge, but these come off easily enough.

Next I put a clean straight edge on all the pieces on my jointer

Then ripping everything to width. I made the shelves 22 cm deep. The Ikea shelves were good for two widths, but the other parts, after cutting off the edge profile, were a bit too narrow.

So I glued some more pieces to the edges. These pieces also had varnish on them. With both pieces the same thickness, I used some clamps across the glued edges to force the two parts into precise alignment.

I planed the Ikea shelves to get a good smooth surface on them.

Cutting everything to length using my table saw sled. I have a small block of wood clamped to the far end as a stop to get the lengths consistent.

Material for the outside of two shelves (they'll be like big boxes).

And naturally, I'm joining the corners of the boxes using my box joint jig.

I have gotten out of the habit of using dado blades for this type of work, and cut my box joints by making a series of cuts with a regular blade using this method.

Each turn of the big gear on the jig moves the stock by 1/4", and I have the positions of the gear marked for hogging out a 1/4" slot. After each 1/4" slot, I turn the gear further until it's 2 turns from the start of the previous slot, and repeat.

A quick test fit on the cut pieces. I didn't actually bother with making a test joint, because I still had tape markings in the right place from a previous project

Box dry fit. Before I glue it together, I want to securely fasten a shelf in the middle.

There's only room for two levels of books in the shelf, so the only logical place to put the shelf is in the middle. As such, no need to make the shelf adjustable.

I'm not a fan of dado joints for this type of joint. They weaken the material too much.

The strongest way to put a shelf like that in is with a series of small mortise and tenon joints, with the mortises parallel to the wood grain. This can be a lot of work, but with the right machines, it's manageable.

I cut the tenons using my box joint jig. But instead of cutting out 1/4" between 1/4" fingers, I cut out 1/2" between 1/4" fingers, for a tenon every 3/4".

The sequence of cuts for this is much the same as for the box joint, except that I'm cutting out two slots next to each other before skipping over where the finger needs to be left. It's too easy to lose track of where one is in the sequence of increments, so I made a paper scale, with a "pointer" of electrical tape to indicate where I need to leave the material. The scale doesn't need to be that precise, I'm only using it to make sure I don't accidentally skip a turn (and a skipped turn would throw me off by a full 1/4")

The tenons need to fit into round mortises in a piece of wood. I manually chiseled the corners off the tenons.

With the right templates and setup, I could have cut these tenons already round on the pantorouter, but it would be a complicated template to make and I only had four sets of tenons to make. It wasn't worth it to make a template.

I cut the mortises on my slot mortiser. The mortiser has enough range to cut a wide series of slots side by side. I used the counter wheel on the crank to keep track of how many turns. I need 12 turns between slots (the threaded rod for vertical adjustment is 12 TPI). The wheel has 32 increments on it, so after the third set of 12 turns, I will have turned the crank 36 times, but the wheel will have returned to zero after 32 turns, so it will read just 4. Still good enough to guard against being off by one turn, and off by 4 turns would be a full 1/4", obvious enough to the eye.

11 mortises cut side by side.

Two mortises would be a double mortise. Had to look it up: 11 is an undecuple mortise.

I glue the shelf into the side pieces first, with glue on both the mortises and in the tenons.

The side pieces and middle shelf form an "h" when assembled.

I'm using my clamping squares to keep it square as I glue it up.

I made a little tool to apply glue to four fingers at once. The tool is just a scrap of wood, cut the same way as the box joints, but with the fingers a bit longer and thinner.

After the middle come the outside pieces.

I clean up the excess glue squeezeout using sawdust from my bandsaw sawdust drawer.

I cut the fingers about 0.5 mm longer than needed and later cut them flush with a (very) sharp chisel. I was able to trim them flush with the varnish that was already on some of the boards without damaging the varnish. This is possible because the varnish is smooth and slightly harder than the wood.

Normally, one relies on the back of a shelf to give it lateral stability. But with the corners all joined with box joints, these shelves are very stiff, able to support my weight across the diagonal.

I needed one wide low shelf, but making it as two units makes it easier to make and move, and, if at some point I need the shelves somewhere else, I can stack them to make a regular bookcase.

Shelves put in place...

... books put on the shelves...

...and couch slid back in place. The couch slides very easily on the hardwood floor, so the books aren't hard to get at. But I really have not been using these books in years, so out of sight and out of mind is just as well. Even if the information I need is in one of my books, I'll still look for it online.

Update 2020

I built those shelf boxes in 2014. Six years and two house moves later, I never ended up stacking them on top of each other. They are currently used as a children's book shelf and as a shoe rack Rachel wanted some dividers in the bookshelf and another level for the shoe rack. I made a video of the work.