Making intersecting dadoes that are not square to the face of the board

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Forum topic by Vrtigo1 posted 07-06-2011 11:57 PM 1149 views 0 times favorited 3 replies Add to Favorites Watch
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434 posts in 3016 days

07-06-2011 11:57 PM

First, a picture because without it I’m sure what I write will be hard to understand…

This is a basic diagram of a wine rack that I’m making. It’s made out of 3/4 plywood and this is looking at it from the front. I’m going to put a face frame and edge banding on eventually to cover the endgrain, but for now it’s as you see it here.

Here’s another picture of the actual project as it sits now. This is just the right side of what you see in the diagram above (nevermind that the solid piece of plywood in the diagram is opposite what’s in the picture, I drew the left side and then flipped it to create that diagram).

I want to put a piece of plywood between the top left corner and bottom right corner, then I want cut shallow dadoes on either side of that and intersect it with two smaller pieces of plywood from the top right and bottom left corners to create an “X” shape. The wine bottles will sit in the top, bottom, left and right cavities.

Since the space where this is going is wider than it is tall, the two “squares” (the left and right side of the cabinet) are rectangles instead of squares. In my head, I thought this through as though they were squares and everything would be nice 45 and 90 degree angles.

I used an online calculator and got the angles at the top left and bottom right corners, they’re 51 and 39. As you can see in the picture of the project, I used a scrap piece of ply and cut the two ends at the appropriate angles and fitted it in there. That much fits pretty well – not perfect, but the face frame will cover up any errors there. As far as the dadoes that will need to go in the middle of that piece, I cut one end of another scrap piece to the appropriate angle, fitted it in the corner and marked where it crosses the first scrap piece. You can see the pencil marks in the middle of the scrap piece in the picture.

My question is what is the best way to go about finding the correct angle for the dado cuts? I have an angle finder somewhere, but I’m not sure how accurate that’ll be. Is there some math that I can use here that will get me to 100% theoretical accuracy (I know nothing’s 100% since plywood isn’t 100% flat)? Or is this just a case of trial and error until it fits?

3 replies so far

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434 posts in 3016 days

#1 posted 07-07-2011 12:03 AM

And part 2 of this question…I wanted to keep the two questions separate…how would you handle the solid wood edge banding on the “X” pieces? Since the two shorter pieces will sit in dadoes in the larger one, should I just edge band the smaller pieces but leave the edge banding off the parts that will sit in the dadoes? That seems like the best way to me since there’s no way I could fit a router in there to flush trim it after they’re installed. I guess that’s why norm always builds more than one…to figure out how to do it from all the mistakes the first time around!

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#2 posted 07-07-2011 12:36 AM

I’ve built stuff like that before – it’s trickier than you expect it to be.

For the angles, I’d avoid trying to figure it out with geometry and make
full or half-scale drawings and measure the angles in the drawings. You
could also use Sketchup and it would help you figure the relationships
pretty well, but it takes some time to learn to use it.

In regards to edge-banding, I would use solid wood about 1/4” thick
and miter the center four ways and nailed/glued. You can get a
router in there to trim most of it flush. The rest you just do with
knives, chisels, and files.

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434 posts in 3016 days

#3 posted 07-07-2011 05:43 PM

Thanks. I trial and errored it last night with scrap and got pretty close. I figured it would be pretty close if I only mitered one side of the plywood where it meets the corners, but doing it that way the top is about an inch smaller than the bottom, so I’m going to give it another shot tonight mitering both sides of the plywood so it sits centered in the corners instead of being offset. Not sure if that makes sense, but after doing it once, I think the edge banding is actually going to be the more challenging part of this project. Thanks for the suggestions. It probably would’ve been easier to put two vertical dividers in instead of only one to make the two ends squares and then just put some square storage bins in the middle. Oh well, hind sight is 20/20.

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