Seeking advise: Building a solid wood trapezoidal case
Building a mid century stereo credenza for my 1960 Fisher. Shape of case is trapezoid with long top and shorter sides. Top acute panel corner and bottom obtuse panels will be joined by angled dovetails (I’ve been practicing this step for months). Two center dividers will be fitted via sliding dovetails and a shelf will span them for the receiver. I will have 3 drawers on the right side of the receiver shelf/divider area. My problem is that I need to place a third vertical divider to support the outer side of the drawers. This divider will need to dangerously close to the bottom obtuse dovetail panel junction. where the top of this divider meets the table top there is plenty of distance from the acute junction due to the shape of trapezoid. I want to fasten this divider with a sliding dovetail to match the other dividers, however I’m concerned about how close i can be to the obtuse dovetail panel junction without weakening the bottom of the case. Plywood would have worked but a friend gave me 400+ feet of 6/4 walnut to burn. Sorry the image is rotated.Thanks
Replies
First, congrats on the walnut, and on the ambitious build!
I hope you don't find me rude to suggest an alternate approach...
If you placed blocking on the angled interior wall to mount your drawer supports you will add considerable volume to the drawers and sidestep the structural issue.
MJ, thanks. That is the kind of advise i'm looking for. Sometimes I just get stumped and need to bounce ideas off someone. I wonder, You think I should just add blocks where the screws from sliders attach or go full width. Any suggestion on how to fasten said blocks to case to allow for wood movement? Thanks again.
I cannot see any reason why that would not work.
Wood, especially wood that wide is very, very strong so you have a decent amount to play with. Also, the piece you are concerned about is the structural member here, and will take most of the weight of the top. The side is not going to take much load.
Whether this is going to be sufficiently strong will depend on the thickness of the bottom of the case and how deep you plan to cut the dovetail.
If you have half an inch of wood under the bottom of the dovetail it should be plenty, short of deliberate efforts to destroy the piece.
If you think about it, the closer your slot to the dovetails, the stronger the case - the failure point would be the bottom of the sliding dovetail slot. The longer the distance between this and the edge of the case, the greater the leverage on the thinner wood.
If you are expecting to put very heavy loads (way more than a stereo) on the furniture, then you could increase the strength by:
1. Keep the sliding dovetail relatively shallow.
2. Leave a shoulder on the sliding dovetail, on the side closest to the legs.
3. Ensure there is a good fit at the top for the upright member - a precise fit will mean all the load from the top goes through this very strong part of the work.
4. Use lots of glue. Movement should not be an issue as the boards should have congruent grain direction.
5. Consider extending the apron (this will look awful though)
As I said though, none of this is really necessary as for what you are going to be using this piece for, it'll be more than strong enough. Assuming your framing material is 18mm (3/4) inch and your legs are fixed on properly, you could probably stand on top of your design and it would not break.
If I were blocking for metal drawer hardware I would make the blocks in the same grain direction as the case and glue it to the case with a (gasp) couple of finishing nails to hold it from sliding up or down when clamping. The blocks should move with the case.
Thanks for the replies, I have some options.
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