Bending 3/4" plywood into right angles with a 4" bend radius

I have an idea for a stylized plywood coffee table that is all made from a single board of 3/4" Baltic Birch plywood. I've attached a .jpg of a coffee table base-design to this email.  The bends on either side are 4 inch radius bends. Although I have basically no experience bending plywood, I sincerely doubt 3/4 inch plywood is going to bend into right angles at a 4 inch radius. I may be wrong, but if it is possible, I do not know how to do it, and certainly do not have the equipment.

I've seen on the internet very flexible sheets of plywood, but wouldn't that just get glued into position and then just collapse once un-molded? I can't believe that I am the only person who wants to do something like this. Any input?

Picture of Bending 3/4
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kenearlg1 year ago

I would try the kerf-bending method. Use a polyurethane glue like Gorilla glue that will expand in the saw cuts. Glue a piece of thick veneer on the inside to strengthen the bend, that might keep it from collapsing. If you can do all that in one "fell swoop" then Bob's your uncle. Maybe use a piece of 8" PVC drain pipe for the inside form.

There was supposed to be a link to a youtube video in my post, that would be

If that isn't allowed, just do a youtube search for "Kerf Bending Wood Parts".

Toga_Dan2 years ago

yeah. glue up veneers. as downunder suggests.

vacuum bagging. when finished, you want it to appear as 1 piece. no seams at the corners.

Dolmetscher007 (author)  Toga_Dan2 years ago

I agree... I definitely think that gluing up veneers is the way to go. However, where does one purchase veneers? Would 2' x 8' veneers, and enough of them to reach a 3/4" thickness not end up making this a $300 half sheet of birch plywood?

I dimly remember the term "doorskins", but a quick look seems to indicate they may not be the same thing they used to be. Perhaps it's just some that are now mostly press board.

Qcks2 years ago

Just a passing thought.... Look up Applied Science's video on Youtube "Bending wood with ammonia", it might help, but i wouldn't call it a beginners project.

Toga_Dan2 years ago

as for veneer shopping, Im not sure where to get it economically. If you can get the stuff thats sandwiched in the middle of plywood, it should be cheaper. It will have voids, defects, etc, but is hidden from sight.

You won't be able to I am afraid.
Even when you steam the wood it will be too thick to result in a proper bend, using laminated single sheets would be the best approach.
If you are not concerned about the look of the inner side of the the bend you try to cut grooves into it.
The grooves should go half way to 3/4 through the wood and be evenly spaced.
Doing a test piece first you determine the spacing and thickness of the grooves, if in doubt I am usually quite happy using 4mm router bit with the same spacing.

Dolmetscher007 (author)  Downunder35m2 years ago

Thank you Downunder35m,

I meant to mention that I had thought of using saw kerfs to weaken the bends to achieve the 4 in radius. I have not ruled that method out yet, but I am holding out for a better method. My issue is, if someone sits on this coffee table, with saw kerfs on the underside, it would most likely bend, sheer, and/or snap. The table must be "rugged" enough to hold a 200 lb person sitting on it.

For more stability you fill the grooves with a mix of the saw dust you created and wood glue (best to add a tiny bit of water to it for longer working time.
Some sticky tape on the sides and over the finninshed bend gives a smoother look.
Once cured sand it down and all is good.

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