Joining Plywood at Angles other than 90° or 45 °

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Forum topic by Mikaan posted 10-24-2012 12:43 AM 7821 views 1 time favorited 13 replies Add to Favorites Watch
View Mikaan's profile


2 posts in 2217 days

10-24-2012 12:43 AM

Topic tags/keywords: box biscuit joiner walnut plywood angles clamp tablesaw joining modern

Hi there,
I have a client that is wanting a bookshelf with a bunch of funky angles ranging from ~61° to 130°. The pieces will be 10” wide and up to 35” long.

I initially ruled out exterior splines because making a jig for each angle to do one cut would be a nightmare.
The only thing I can think of is biscuits but I don’t have enough scrap lying around to test it out. Does anyone have insight on this, what joinery to use, how to ensure proper glue surface/contact? The lack of information I found is what is scaring me more than anything else.

I’ll attach a file so you get a better idea. Any help is greatly appreciated.

Thanks for your time

13 replies so far

View Loren's profile


10477 posts in 3824 days

#1 posted 10-24-2012 12:47 AM

It’s the clamping for tight joints that makes such assemblies

Sometimes it’s better to say “no” if you don’t feel up to
the work or there isn’t enough money in the job to compensate
for the development of specialized jigs to do it right.

The acute corners will be fragile. I hope you are not
planning to do this in ply or in anything less hard than
solid oak. I also would think more in terms of 1” material
thickness than 3/4”.

Throwing aside the acute miters, this piece could be
dovetailed by hand in a relatively straightforward matter.
Whether the client will pay for it is another matter.

View Grandpa's profile


3261 posts in 2851 days

#2 posted 10-24-2012 12:59 AM

The first thing I thought while the photo was loading was a comment my friend made. He felt bad when he didn’t get every bid he made then he finally realized he was better off wiothout some of those jobs and this might be one. Then I saw that Loren made basically the same comment. I would have to charge a premium for this case.

View Mikaan's profile


2 posts in 2217 days

#3 posted 10-24-2012 01:30 AM

I totally agree with both things said. However just to clarify, and I’m not sure if this makes a difference, but I don’t want to miter them. Only 1 piece will be cut to form each angle, the other will be left square and be edge banded on the outside. I know this will look funky but I’m goin for a mid century look and funky stuff like that showed up from time to time.

As far as clamping and assembly, I think i will do the shelves as adjustable and use shelf pins or dado them in. The back will be 1/4” and ill reinforce the back with 3/4” nailers pocket screwed to the sides. so I’m not too worried about structural support. I’m going to fork over $20 for a sheet of construction grade ply and just make a scaled down version to try it out.

Thanks for the help everyone, I can never accept no as an answer though (ill probably he back in a week encrusted in glue and walnut saw dust yelling at you guys for not talking me out of it)

View waho6o9's profile


8487 posts in 2753 days

#4 posted 10-24-2012 01:35 AM

Great reason to purchase a Domino.
Easy peasy.

View cabmaker's profile


1740 posts in 2985 days

#5 posted 10-24-2012 01:47 AM

Looks pretty straight forward from here. Dowel jig would probably be quickist, but spline is easy enough too. I think I would dowel but were I splining I would clamp a 3/4 inch thick falloff to one side of the bevel joint and run it with a router and 1/8 inch straight cut bit. The falloff peice I mention would of coarse need a matching bevel so it would provide support for the router. Hope this makes some sense to you. Again, doweling jig is pretty fast and idiot proof. Plate joiner would certainly work but I dont think you would gain the structural integrity the dowel would give you in your situation. JB

View Moron's profile


5032 posts in 4069 days

#6 posted 10-24-2012 02:23 AM

I feel like everyday I work in a world of “Make Believe” and this web site is sometimes refreshing to read.

A world where a designer puts thoughts to paper and architects put pencil to paper only putting both to the practical application of the idea, and implementing it often leaves big voids ? Where not even Festool can fix it.

When I hear the word “client”, it engages a thought process where in the same sentence, I also hear the word “nightmare” conjures memories of STOP…..breathe……think.

I really like the drawing and its eclectic nature, almost whimsical, deserving of a hobbit and a piece of furniture I personally would like to own. Woodworking professionally, is increasingly like a game of poker, and knowing when to fold, hold, and increase the bet, is nothing more then experience gambled : )

2 cents

-- "Good artists borrow, great artists steal”…..Picasso

View GrandpaLen's profile


1651 posts in 2448 days

#7 posted 10-24-2012 05:17 PM

As far as clamping and assembly, I think i will do the shelves as adjustable and use shelf pins or dado them in.

IMHO, according to your SU drawing, without horizontal support sides being paralell I don’t see the shelves being adjustable. You could use metal shelf supports and shelf brackets but your shelf length will limit the adjustability.

Best Regards. – Grandpa Len.

-- Mother Nature should be proud of what you've done with her tree. - Len ...just north of a stone's throw from the oHIo, river that is, in So. Indiana.

View Earlextech's profile


1162 posts in 2866 days

#8 posted 10-24-2012 05:33 PM

I would add 1” of solid wood at each end of the case parts, thereby giving you something to work with for the joinery.

-- Sam Hamory - The project is never finished until its "Finished"!

View GregD's profile


788 posts in 3312 days

#9 posted 10-24-2012 05:52 PM

Here is a different idea…

For each corner: Take a board, say 4” wide and cut to length (depth of bookcase). Cut centered grooves into each edge. Rip the board in half, and then bevel the ripped edges. Glue the bevels together to get the desired corner angle. This might be a bit fussy, but the parts are small.

The plywood boards that form the bookcase sides are cut at 90 degrees, and machined to form tenons that fit into the grooves of the corner assemblies.

-- Greg D.

View MrRon's profile


5141 posts in 3419 days

#10 posted 10-28-2012 06:13 PM

Splines would be easy to do if you have a radial arm saw or a sliding compound miter saw. I like Gregd’s idea of corner assemblies. No way can you get adjustable shelves with sloping sides. If you go with corner assemblies, consider using a contrasting wood, like Ebony; otherwise you will have a grain mismatch, and if you do attempt this job, charge double your original estimate to cover mistakes you will make.

View RussellAP's profile


3104 posts in 2462 days

#11 posted 10-28-2012 08:13 PM

I agree with loren about thicker ply or solid wood. At least thicker ply.

What kind of material is the back made from. Is it thick enough to give structure? If not, run a couple braces up the back vertical to support the shelving. You can hide behind the back. 1×4 should do it. Then you can just glue up the miters.

-- A positive attitude will take you much further than positive thinking ever will.

View RussellAP's profile


3104 posts in 2462 days

#12 posted 10-28-2012 08:19 PM

You might also consider a face frame which would give more tolerance to any uneven joinery in those weird angles and allow you to add a reinforcing strip to the joint being glued or doweled on the inside where it cannot be seen, and you could clamp it up easier that way too.

-- A positive attitude will take you much further than positive thinking ever will.

View RussellAP's profile


3104 posts in 2462 days

#13 posted 10-28-2012 08:26 PM

Another thing to consider and another reason for a face frame is; once you cut the upper side board on the left, the funky angle one, there will be an offset because the wood you cut at an angle has more area now on the end grain. The face frame would hide that and also hide any reinforcing strips you add for that weak joint.

-- A positive attitude will take you much further than positive thinking ever will.

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