Hi everyone, I've got a question that I can't seem to find an answer to on the web.
I've been asked to make a set of desks and tables for a new office, including a large conference room table. The desks and tables will be made with solid wood tops, however the conference room table I'm not sure about.
The dimensions are 120" x 48". It will be attached to a welded metal frame - so I don't have to worry about that part. My question is, at what size does a tabletop become too large to be made from solid wood. I'm obviously concerned with wood movement and warping over the life of the piece. Should this size top be made using MDF or plywood? I've been considering torsion box construction with MDF. On top of which I would glue birch ply to allow for veneering (I've read that birch ply is better to veneer to than bare MDF).
I don't think I would consider making a conference table out of solid wood with so many other less difficult to manage and cheaper options. Although I am not a professional, if I was doing this, I would use MDF for this project. I'm not sure where you received the info about veneering on MDF but I would most definitely question that. MDF, although I have no love affair with the material, is probably the best substrate for veneering due to its consistency and flatness. Just to demonstrate, the A1 cabinet wood veneers above 1/4 inch are almost entirely always on an MDF substrate. If you veneer over plywood, there is potential to hit a void that telegraphs to the top. I just don't think it is worth it to take the risk on such a large project. To ensure flatness, make sure to veneer both sides.
Make a torsion box assembly, and use hardwood veneered plywood top and bottom. Then use solid wood edging. That size table is going to be a nightmare to transport/move around out of solid wood, solid ply, or solid MDF. I'd make the torsion box part out of ply as well rather than MDF.
I agree with Mike that making a solid wood table, especially of this size, is asking for problems. However, like jmartel, I would use hardwood plywood, not MDF. Unless you are well equipped and experienced, veneering such a large surface could be unwieldy.
I would even question the efficacy of using solid wood for the desks. Plywood is stable and won't change dimensionally according to the seasons.
If I were using birch ply under the veneer, I'd simply stick with it for all the hidden parts. I also question the general "ply is better" statement. LOTS of conference tables and other office furniture are veneered MDF.
Either sheet material has worked well for me under veneer, I'd base my choice more on span distances, etc… over how the veneer will look or stick to it. Are you vacuum pressing the veneer?
To me, the veneer vs. solid wood question really comes down to the final look expected by the client. Lots of conference tables have a band or feature strip inlayed, or some sort of grain direction manipulation. There are some less common looks that would absolutely look better in solid wood.
As for the final look of the piece, I still need to discuss with the client what they want that to be. I don't remember where I read that plywood is better for veneering, but there was a recent FineWoodworking article that stated MDF is a better substrate for veneer - so there ya go.
While using veneered plywood seems to be the easiest solution, I'm not sure if I'll be able to get plywood with the desired veneer. I have some experience with veneering, but it was done with a clothes iron to attach the veneer - I'm not sure if that's a viable option for something this size. Since I'm not handling the metal table frame, I'm not sure yet if there is a center support which would make this process a little easier - being able to divide it into two 5' sections.
I'm in the process of rebuilding my website, and happen to be working on this page, so I thought I would pass it along. We 've used the same process for conference tables as well.
Why not over plywood? Telegraphing?
I did this table over ply and thought it worked very well. (Pretty sure it was maple ply but don't remember)
Your way more knowledgeable than me so I respect your opinions.
Plywood isn't as flat as MDF and particle board. Getting that dead-flat, water-level surface requires a dead-flat surface underneath as the veneer isn't thick enough to level out anything. Strength-wise, plywood is superior. I'd have to pick through several sheets of plywood before finding one that I'd consider acceptable for a conference table. Without a wide-belt sander, I can't flatten sheet stock before veneering.
If using plywood, be sure to glue cross-grain to the plywood surface otherwise you'll effectively end up with what amounts to a thick piece of veneer on the outside which may be more prone to expansion issues.
Make a torsion box assembly, and use hardwood veneered plywood top and bottom. Then use solid wood edging. That size table is going to be a nightmare to transport/move around out of solid wood, solid ply, or solid MDF. I d make the torsion box part out of ply as well rather than MDF.
Will also hold up to moisture\humidity better than MDF, as well.
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