Nightstand Tabletop construction - This Okay?

[Brody Goodwine]

I'm planning to build some nightstands with approx 18" x 18" tops. I have some bookmatched pieces of quartersawn Sapele 0.44" thick I'd like to use for them. What i'm planning to do is glue them directly to 3/4 MDF to get enough thickness for the top. I'll edge the top with cherry most likely.

My question is if there are issues (specifically movement) I'm failing to consider.

[Paul Murphy]

I've not tried what you propose, but conventional wizdom is that somewhere above 1/8" veneer thickness the forces of seasonal wood movement become strong enough to overcome the glue.

[Brian Tymchak]

Brody,

It is fairly typcial to veneer the opposite side of the substrate with veneer of equivalent thickness (but maybe a less costly species) so as to balance the stress on the panel or it will want to warp as the veneer shrinks/expands with seasonal humidity changes. google up "Joe Woodworker backer veneer" for a discussion on this.

Brian

PS: Just saw Paul's response and realized I misread your original post as veneer at .044, not the nearly half inch thick material. However, I think the seasonal movement will still be an issue, maybe more so since you have nearly half the thickness of your panel wanting to move and the other half not.

[Brody Goodwine]

The top is only about 17" x 13", and the sapele is in 2 pieces, each about 13" x 9". The thickness is .44" Do I have any options?

Is the glue surface so large that it'll definitely create issues, even in a bedroom? The humidity moves a little ~15% in our house, but of course the temp doesn't.

[Lee Schierer]

I'm not familiar with how much Sapele moves with moisture changes, but if you are planning to have a3/4" MDF substrate then you are also planning a frame around the sides. I would glue the pieces together to get the width I wanted and then make a floating flat panel supported , but not glued to the MDF so the real wood can move seasonally. Make the frame so it overlaps the edges of the panel sufficiently to hide any movement. Use space balls on the sides to keep the top panel centered.

[Brian Tymchak]

The old rule of thumb that I had always heard was the wood will grow/shrink about 1/8" per 12" across the width. Since you have quartersawn maybe it moves only half that, but still moving none-the-less. MDF won't move at all, so I think you will have some issues that you should take into account.

I'm quickly getting to the limit of my "expertise" on this topic. But, I can offer a suggestion that I have not personally tried (maybe someone has and can comment) and that would be to back up your Sapele with a common hardwood. You mentioned using Cherry for the edge banding. That might work for a backer board as well. On second thought, maybe something that is more commonly available as quarter sawn such as Red or White Oak would be better to get a closer match on the seasonal movement. (I think we're talking about radial movement being a quartersawn board.) If you want to get really into it you can google up the radial shrinkage of different woods to find a close match so that the backer board will move at pretty much the same rate as the Sapele. I use wood-database.com occasionally for wood info. And then of course secure the top with hardware or a technique that will allow movement across the width of the board.

[Jeff Duncan]

Wood that thick will move, so that part is what it is, and will likely cause problems being glued to mdf. Now on top of that I believe your talking about wrapping all 4 edges with solid....again the wood IS going to move and either spread those solid edges apart or leave a gap between them.

The solution....get the materials to fit the design. To do a flush top with solid edges you want to use veneer for the top on your mdf blank. This is the way tops like this have been made for ever and will work.....anything else is just experimenting at your own risk without consideration for long established good technique

good luck,
JeffD

[George Gyulatyan]

Do you have a bandsaw? If so, I'd resaw those pieces into 1/8" or thinner veneer and apply the veneer to MDF.

At almost half an inch you're asking for trouble if you glue the pieces to MDF and not allow for any movement.