Slot Joint Adjustable Bookshelves





Introduction: Slot Joint Adjustable Bookshelves

About: I believe in slow craft, carefully observed hand made objects. Currently I'm an Artist in Residence at Autodesk Pier 9, San Francisco, CA where I am learning to understand Computer Aided Machining, additiv...

We love our loft apartment, but it only has one closet. So we have to get creative with clothing and book storage. A large shelf was a good solution for stacking folded clothing and other things. Living in a loft we were able to make a 8ft tall shelf.

I found some inspiration from New Zealand designers Pedersen Lennard (shown above in the two staged photos) I adjusted the design to meet my needs, which were to make a simple shelf that is "quick and easy" to make and requires no hardware. The intention was to hold clothing (for now) and later become a book shelf, so an adjustable shelf is perfect.

This shelf is made entirely out of Apple plywood, a dense high grade Russian birch in 3/4" thickness. The shelf I made is 8ft tall by 5 ft wide and 14" deep. All joints are slot fitted and have dog-bone fillets for ease of assembly.


4 Sheets of 4x8' Apple Ply - $493.88

Brass Brackets $11.10

Polyurethane Satin Coating + Misc rags, brushes. $45


Step 1: Cut Out Vertical and Horizontal Slotted Parts

I wanted to cut these shelves on a ShopBot (CNC Wood Mill) not because the design requires it, on the contrary the shelf pieces can be easily made in a traditional wood shop, but because I wanted to get comfortable with the Shopbot work flow and make something that would be easy to generate code for and cut.

I drew up the the shelf plans in Fusion360 and exported them as .DXF files. I imported it and generated .Sbp files with my tool settings, and particular feeds and speeds. * I highly suggest doing this process on your own and generating new G-Code to make sure its correct.

Since this piece requires no hardware and needs to have slot joints that are snug but not too tight, you need to measure and adjust your tolerances on all the slot gaps after measuring your plywood with calipers. I find that 3/4" ply can vary quite a bit, even when ordering a new batch from the same supplier. If your tolerances are too tight later you will need to sand the slots for a while which takes extra time.

I have included drawings so you can look at my exact measurements if you like.

Step 2: Sanding, Sanding Then a More Sanding

I wanted a smooth finish on all surfaces so I sanded every piece with 220 grit and 320 grit using an orbital sander. The important part is the sides where the cuts were. They are a bit trickier to sand and require a bit on hand sanding between the cuts. I also tested my small shelf to make sure the shelf tolerances fit together.

It took a while to sand between each slot and on all sides.

Step 3: Sealing and Assembly

I used Minawax Poly-urathane satin finish, applying 2 coats to each side with a foam brush, sanding with 220 and then 320 grit between coats, sealing each side 3 times. This took several days and was not easy to do right on first try.

Pro Tip* I found that using a wipe on poly-urethane or an oil/wax based finish like (Rubio Monocoat) is better then the foam brush application which will drip and streak. If you have the option use a wipe on sealer and apply several thin coats with a cotton rag to get a smooth finish. Light sand with 400 grit for final smooth finish if necessary

As always, safety first! Wear gloves, a respirator and apply any chemical finish outside or in a well ventilated area.

Once all parts are fully dry, allow at least 24 hours to fully dry.

Assemble shelf and voila!

Pro Tip. If your shelf slots are too snug and require force, grease all joints with a bar of soap and try assembling then.



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    17 Discussions

    Great design. I'm thinking of using something like it in conjunction with a desk. Could you provide more information/details on the brackets you used?

    Wow ... i designed the same shelf (yes - exactly THIS) at a design-school and got a very bad note. Now I see your project and I'm very happy, that you got so much positiv feedback. And, of course, it's nice to see it in real! Thank you for sharing it! :)


    2 years ago

    Hmm so greattt

    Why OH Why did you spend so much on plywood? Birtch, Oak and Maple are all less than $60 a sheet from Lowes or Home Depot.

    1 reply

    Yes I am aware what HD carries- I got much nicer higher grade ply, and the budget was covered so I didn't mind the steep price. You can do as you wish


    2 years ago

    For those who are looking to use lower cost wood I would like to suggest making use of pins towards the rear or on back board if you add it, as shown in the following link. Mind you this is just for the picture to give you an idea. I bought some of these in Home Depot. You could in turn cut shallower slots in both the verticals and the horizontals. This should reduce the distorting torque in the slots of the wood. You would have to calculate and drill the necessary holes as required.

    1 reply

    Why not put holes in the backboard and pegs in the rear edges of the shelves? Self-contained and nothing left sticking out when the shelf is moved.

    This looks like a great idea.

    I have a technical question. I'm working on another CNC project. How were you able to add the dog bone fillets? I've tried to find that option in several different programs, but haven't had any luck.


    2 replies

    Hi, My CAD drawing didn't have fillets drawn in, it's something I added In CAM software when generating tool paths. I added the dog bone fillets in Carve 3d the shopbot CAM software here at pier 9, it was quite easy in that software, I selected fillets option, picked the dogbone kind set diameter and clicked on each corner or the geometry, which added perfect Dog bone fillets- what software are you using?

    I'm actually modifying some plans I found online. I've been using AutoCAD for the vector work, but our FabLab uses VCarve from Vectric Ltd. to run the CNC machine. we couldn't find the fillet option on VCarve, so I've been modifying the actual vector files to include the dog bone fillets.

    Ideas like this need patent protection and could generate billions for lumberyards with NC programmed power saws. You could collect a nice income just on a straight commission basis. As a bibliomaniac with enough hardcover nonfiction to easily start a consignment used bookstore this would fit me to a "T".

    Here are a few constructive comments, however, for those of us with limited resources and living in the real world. First of all, if you're careful, I think you could just use an ordinary skil saw instead of a fancy NC woodshop. Secondly, I'm not so sure you would have to use such expensive plywood although furniture grade 3/8" would be less likely to warp and much prettier to look at. Finally, if the cheaper, uglier plywood DID suffer from structural weakness, maybe you could sacrifice some of the flexibility by attaching a back to at least some portion of the unit holding at least part of it together with some of the new fastners of the e.g. deck screw variety.

    One last critique deals with the ambiguity of your precise horizontal and vertical dimensions. The screenshot schematic is very hard to read and I assume the vertical spacing between slots is metric rather than SAE.

    1 reply

    Hi thanks for your comments. Yes it can certainly be made with hand held power tools! I am not looking for income so you are welcome to use the design as you see fit, this is why I shared my drawings with everyone:) it's not really my design to patent-
    I don't disagree, if you want to use thinner ply and add hardware go for it, but it's something I specifically wanted to avoid.
    Lastly, my measurkents are all in inches.

    The vertical parts are 10" deep by 8ft tall and are spaced 16.5" appart. When measuring from the inner dimension of vertical shelf.

    The slots in the verticals are 6" appart, I believe-

    My horizontal parts are are 14.5" deep and vary in length depending on shelf. You can open the illustrator or .dxf files to get precise measurements.

    Wonderful idea...400 is a lot for those plywood sheets. Do you think a thinner grade would have worked for you too?

    how do the dog bone fillets help?

    are the brass brackets used?

    1 reply

    Hi, yes I too was surprised how much the grade A ply costs, I wouldn't recommend a thinner ply, if you are looking to save some money you can use a lower grade plywood. But I wound not use a thinner one as the structure has no other supports or backboards besides the 3/4" shelves. This keeps it all study and straight.

    The piece has no hardware in it but the brass brackets should attach to the vertical shelves and anchor into the wall/ ( see intro: photo 2/3 to see how their black steel braketts attach to the wall) good luck!


    2 years ago

    I like the design. Noticed however that you don't have a backing board or any other support to keep it square and not tumble sideways. Is the snug fit of the boards strong enough to provide that strength?

    1 reply

    Yes! The slot joint tolerances are tight and as soon as you add two verticals the whole thing is sturdy and squared up. I would however suggest adding brackets and screwing the entire shelving unit to the wall so it won't fall over when fully loaded!