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Discussion Starter #1
Hello All. Starting a new project and could use some advice. I want to make a table using lots of exotic hardwood pieces for the top. Its going to be a large table 12' x 4'. I already made the table top substrate out of 3/4" oak plywood and framed the edges with 2x4's. My plan is to glue the individual pieces of hardwood to the oak top.
My first question is will the pieces glued to the top last over time or eventually pull up. Secondly I am having trouble coming up with a way to actually clamp little pieces of wood in the middle of the table. I would like to build a jig system of some kind that would grab both sides of the Oak base and then have a board going across table with sliding clamps. Havnt seen a clamp that might work for that.
Any help would be much appreciated
Thanks,
Jake
 

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It would be difficult to say how durable the table would be gluing pieces of wood to the plywood. The table would only be a durable as the veneer on the plywood and the plywood that is manufactured today is pretty crummy. For sure don't use any Chinese made plywood. Probably the biggest problem you are going to experience is the plywood warping from doing this. The plywood will need to be clamped to a flat surface as well as clamping the pieces on. I would also recommend using a resin glue for this. It will dry harder and drier than wood glue would. The jig you described sounds like what I normally use for this type of gluing. I just cover a block of wood with clear plastic package sealing tape so it doesn't stick to the wood and span a 2x4 or 2x6 edgeways across the panel and champ it on each end with pipe clamps. For shorter spans there is a welding clamp which looks like vice grips with a 12" reach that you could use. If the wood fits really good you could also use a cinder block and just weight it down. It doesn't take a huge amount of pressure.
 

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To hold down the pieces in the middle, use your idea of a 2x on its edge that hooks onto the oak plywood, then each little piece that is under the 2x use opposing shims or wedges between the 2x and the piece you need to hold down. No clamps needs, you can hold down multiple pieces at one time, and wedges are easily made (just make sure they are smooth so they slide easily on top each other) or just go buy a pack of shims for installing door frames.
 

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How small/large are the pieces you want to work with? My concern with what you want to do is wood shrinkage. The larger the pieces the more the shrinkage and the larger the eventual gap between pieces.

I think that this problem is possible acerbated by using many wood types.

I am sitting here looking at a door I made on a computer desk many years ago. I wanted to get fancy an use small pieces of oak in patterns to give a different appearance. Some of the wood shrank and I now have a crack around one half of the diamond shaped middle piece.

Interestingly, there are two doors made like this and the other had no problems.

Gluing to a substrate will not solve this problem. That was another lesson I learned many years ago.

You could possible minimize any future problems be first acclimatising the wood to the environment where the table will be used.

George

George
 

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Discussion Starter #6
I'm thinking different size ranges from 4"x4" on up. Lots are in boards and was going to lay everything out first to see what sizes. I also have lots of scraps I'm glueing up to make bigger size, that should help add some more issues, ha ha. Sounds weird but I thought I liked the rougher look of not tight joints anyway and was thinking of filling gaps with mineral in lay or colored epoxy.
 

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Hmmm I am with George. Wood shrinkage would be a major concern along with bracing for the plywood. 12' is a big table and a lot of material to dive into. I would make a smaller test...maybe a little end table to try and work out the bugs.

Sent from my DROID RAZR MAXX using Woodworking Talk
 

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Discussion Starter #12
That would be the smart thing to do. I have a good solid base of concrete block with metal supports that the table is go to be sitting on top of. I just removed the plywood part so I could work on it in my shop.
 

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Discussion Starter #17
First of many coats of Epiphanes. Had trouble getting it to stick to the Cocobola wood. Must be too oily. Tried wiping with acetone but ended up putting a light coat of west epoxy across whole table. Epiphanes customer service was horrible and no help. Guess they don't deal with hobbyist much. Cocobola is a beautiful wood but along with being difficult to seal it made my eyes swell shut and face burn even with a mask on, ha ha. Also ended up thinning epiphanes 20% and spraying with gun because i couldn't get finish lines out with brush or roller.
 

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George, you are absolute correct on both counts. Gluing individual blocks of solid wood to a composition material like plywood is prescription of failure. The hardwood blocks will want to expand and contract due to changes in relative humidity. The composition substrate will not want to move and will attempt to prevent the solid wood panel from moving. This force will cause warping, glue line failure or some other problem.

A second issue is that surrounding the block panel with a solid wood edging is another no-no. The solid wood panel blocks will want to expand across the grain forcing the cross grain part of the frame split. You can't solidly glue a cross grain board to a solid wood panel.

I'm afraid that attempting the project as described will lead to continuing problems for the original poster.
 
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