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So I'm building this bookcase. Birthday/wedding present for my middle child. bookcase

Sides are bamboo (originally supposed to be hotel stair treads) 6' x 11" x 1"
Horizontals are African Mahogany. 10.5" x 1" x variable length.
Sides lean out @ 15 degrees. 11" spacing between the shelves.
Total weight of the bookcase is ~105lbs. Add 100lbs(?) of books.

I saw this design online a few years ago, and of course cannot find it again to see how he did it.

Tools and skills

Typical homeowner tool selection. Drills, table saw, circular saw, Kreg pocket jig, a dozen big clamps, router, sanders. Not averse to buying something new to get this done.

Skills = just on the unskilled side of 'medium'. I can build a mean deck.
Aircraft mechanic and computer programmer (engineering mindset).

Degree of difficulty - the vertical sides cannot be replaced. I only have the two, and so cannot screw up any holes or cuts. The shelves, I have spare material and can get more. At $7 bd/ft, my wallet would cry, though.

How to join the horizontals with no visible means of support? No visible stiles, braces, brackets...

My current thought is pocket screws from under each shelf, into the bamboo sides. I have enough extra mahogany to create enough sawdust to mix with glue and plug the pocket holes.

Secondary thought is screws from the outside of the sides, into the end grain of the shelves. This also involves somehow covering over the screw holes with matching (something). Of course glue with whatever solution.

Due to the off angles, I'm not sure I could pull off dovetails or mortise and tenon.

Other joinery options? Convince me why pocket screws will not work or are a bad idea.

After much cutting, swearing, and sanding...figured you guys would like to see the finished product in its forever home.

enter image description here

In answer to the actual "question", I went with dowels.

3/8" x 2.5" long, through the side panels. enter image description here

Added in progress:

Full size mockup with cheap 1x2 enter image description here

Side panel strength: 70" span, supported only at the ends, 195lbs of me in the center. 12mm sag enter image description here

Glued and drying: enter image description here

In its forever home, loaded with 100+ hardback books. Look Ma! No collapse! enter image description here

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  • I would do this with dowels. All the angles are the same, so it's worth making a couple of jigs to get everything consistent.
    – user464502
    Apr 19, 2018 at 8:55
  • Obviously M&T joints would be better (arguably the best option) but they'd be tricky to cut to say the least and there's no reason the couldn't be done with pocket screws and have it be strong enough — plenty of screws to spread the load. So if that's the method you're most comfortable with then go for it. I would suggest however not using wood dust and glue for the filling, unless that's your only option. Long-grain plugs look so much nicer if the fit is good.
    – Graphus
    Apr 19, 2018 at 12:26
  • Absent any real negative votes for the pocket jig, I think that's the way I'm going. And with actual plugs instead of some hacked up good with sawdust. Dowels are a strong second choice.
    – NewbWoodie
    Apr 19, 2018 at 21:56
  • Yes dowels can also work nicely to fill pocket-screw holes. Note that this exposes end grain, not long grain, so they will go darker even if they're the same species as the board they're glued into. For this reason I think one of the best options is to accept they'll be visible and go with it, make them a feature by deliberately going with a lighter or darker species.
    – Graphus
    Apr 20, 2018 at 18:02
  • Nice work! Thanks for the in-progress updates and the pics of the final product.
    – FreeMan
    Sep 6, 2018 at 19:50

2 Answers 2

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Another vote for dowels here. It's about as easy to use dowels as it is to fill pocket screw holes with dowels. Just dowel the joints and skip the pocket holes, or use both. Screws aren't a great option for shear-strength - I wouldn't rely on screws to hold up a shelf without dadoes, supporting rails, dowels, or something more structural.

What's your plan for controlling parallelogram stress here? Usually a back panel is the option. Without something like that, you need very serious joints. Pocket screws don't cut it.

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4
  • I agree that screws aren't a great substitute for joinery normally, but here there'd be so many of them and the load would be spread across all, not localised in any one area. Plus the screws usually used in pocket holes are much much stronger than common woodworking screws as they're tool steel not mild steel. Buuuut on the other hand I read the Question again and it does call this a bookshelf when I was visualising much lighter loads for shelves of this style.
    – Graphus
    Apr 26, 2018 at 14:04
  • I've shifted away from pocket screws, and am going with dowels. 3 each at each end of the shelves, 3/8" x 2" oak dowels. Unless, of course, you guys think I need more at each end of the horizontals.
    – NewbWoodie
    Apr 27, 2018 at 14:22
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    For what it's worth, there aren't any parallelograms in the project, so those stresses don't apply. Much.
    – WhatRoughBeast
    May 9, 2018 at 21:52
  • Haha true, thanks for the correction. What's the term I'm looking for here, trapezoidal collapse? shear strength?
    – Andy Hilal
    May 10, 2018 at 22:40
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I'd suggest setting your shelves into the uprights with a dado joint. You'd rout a channel into the uprights for each shelf, and bevel the ends of your shelves at 15 degrees. It would have as much glue surface as a mortise and tenon, and you'll get a rock solid joint.

I did something similar 20+ years ago for the steps in a ladder for a set of cherry bunk beds. (I know, I know :-). You can see the wear and tear in this picture, but the joints never budged.

enter image description here

In this design, the steps project out beyond the uprights, so the dado goes all the way through.

It looks like your shelves are set flush in the back and inset back a half inch in the front. So you'd have to rout the channel "blind" in the front, and square it off with a chisel. Overall, it's a bit more work than dowels, but it would be significantly stronger.

Good luck with whatever you decide to do.

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