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Discussion Starter #1
Glued up my table top Tuesday evening. Looks like this. It's just the table top glued up, the rest is just clamped so I could get a look at how it's coming along. Anyway, should I let it set til Monday before worrying about leveling it, or is it okay to start attacking it tomorrow do you think?

Worried about the moisture from the glue changing the shape after I level it and it dries out.

Dimension = 2" x 23.5" x 35"

http://imgur.com/bgNRlEM
 

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If you glued it Monday you can work on it Tuesday, or late Monday if you did the gluing early Monday. (unless you are using some type of special slow drying glue) Of course I guess this depends upon what you mean by "leveling it."

George
 

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Is the table crowned after gluing or is that just barrel distortion from the lens?

If the table is crowned I would wait a few more days to see if it will level out by itself.
 

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Discussion Starter #5
Is the table crowned after gluing or is that just barrel distortion from the lens?

If the table is crowned I would wait a few more days to see if it will level out by itself.
Probably barrel distortion. I've flipped the sucker over many times and taken a level across the surface looking for light. If anything it is slightly propellered - partly from some shifting during glue up.
 

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If you glued it up on Tuesday then the wood you inlayed in has swollen up making the top crown. I believe the only solution is to put a couple pieces of hardwood on the underside with shems and put screws in the center to put some down pressure on the middle. Something is needed to equalize the pressure the inlayed wood is putting outward. You might also wet the underside of the table to raise the moisture content there and see if that helps.
 

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You may have to overbend it with clamps in the middle. It could have been by the way your clamps were set up on the edges for the glue up. If there was more clamping pressure on the bottom of the long edges instead of center, it would force the cross section to bow up. Could have just been too much clamping pressure.






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Discussion Starter #8
You may have to overbend it with clamps in the middle. It could have been by the way your clamps were set up on the edges for the glue up. If there was more clamping pressure on the bottom of the long edges instead of center, it would force the cross section to bow up. Could have just been too much clamping pressure.
I am guessing this means to span the bottom with a board and clamp 2-3 clamps just in the middle? Would that be a permanent solution - seems like it would just rebend once I take the clamps off? I made have clamped it too hard, I can see myself being guilty of that.

I did take a closer look this afternoon. Definitely a small bow, maybe as bad as 1/16". Any suggestion on a general time-frame to address this? If I do the "overbending" how long would it need to set? I am supposed to bring it to a place monday to run it through their panel sander...
 

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Discussion Starter #9
Just wanted to give closure to this and say thanks to those that helped.

I waited til Sunday with no measurable change in the top. I think Cabinetman nailed it - I goofed in glue up. I ended up making a router sled and having to take 1/8" off the top and took it to a panel sander Monday to true up the back side.

You ain't livin' if you ain't learnin'!
 

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I can't tell by the picture, but it looks like cherry inlays in a maple table...am I right? Here are a few things I notice. I am not sure of the difference in expansion/contraction factor of cherry vs maple (or whatever the woods are). If the two woods expand/contract at different rates, that will cause bowing. Next, from the picture I see that the growth rings on the ends of the boards are all curving the same direction. That will also cause excessive bowing. You should flip/flop every other board so the growth rings oppose each other every other board. This will cancel out bowing all in one direction. The way you store that glued up panel will affect the bowing. If you lay it flat on a table, the exposed side will either expand or contract at a different rate than the under side due to humidity differences on the table surface vs. the air/room humidity.

I have seen all of these things happen at different times. Depending on how you attach the top to the frame, you may eliminate the problem or see the top tear loose from the screws. Make sure you finish the top and bottom sides with equal amounts of finish coats. If you only seal the under side, you create more problems that can cause bowing.
 

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For what it's worth, 1/16" over that width doesn't sound bad. It's hard to walk the line between applying enough clamping pressure to bring everything together and applying so much pressure that it bows in the middle. If bar or pipes on your clamp can bow over that distance, having some bow in the assembly is almost guaranteed. Using Bessey clamps or their Jet equivalent is the best insurance against bowing and even then, it's not impossible.

That table is really nice looking. I really like your design and execution.
 

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Discussion Starter #12
I can't tell by the picture, but it looks like cherry inlays in a maple table...am I right? Here are a few things I notice. I am not sure of the difference in expansion/contraction factor of cherry vs maple (or whatever the woods are). If the two woods expand/contract at different rates, that will cause bowing. Next, from the picture I see that the growth rings on the ends of the boards are all curving the same direction. That will also cause excessive bowing. You should flip/flop every other board so the growth rings oppose each other every other board. This will cancel out bowing all in one direction. The way you store that glued up panel will affect the bowing. If you lay it flat on a table, the exposed side will either expand or contract at a different rate than the under side due to humidity differences on the table surface vs. the air/room humidity.

I have seen all of these things happen at different times. Depending on how you attach the top to the frame, you may eliminate the problem or see the top tear loose from the screws. Make sure you finish the top and bottom sides with equal amounts of finish coats. If you only seal the under side, you create more problems that can cause bowing.

It is maple and padauk. I had thought about doing cherry though.:yes:

Seems a bit harder to tell in the picture - I actually did take the time to alternate grain the best I could. If I recall the two end maple pieces are the same direction because how milling the stocked turned out, I couldn't flip it because the bottom has some bad stuff going on.

Thanks also for the heads up on the finish. That seemed to be an issue for some as I was reading on these forums. I'll make sure to do even coats on both sides.

For what it's worth, 1/16" over that width doesn't sound bad. It's hard to walk the line between applying enough clamping pressure to bring everything together and applying so much pressure that it bows in the middle. If bar or pipes on your clamp can bow over that distance, having some bow in the assembly is almost guaranteed. Using Bessey clamps or their Jet equivalent is the best insurance against bowing and even then, it's not impossible.

That table is really nice looking. I really like your design and execution.
Thanks for the encouragement. I only have cheap bar clamps and 2 pipe clamps. It's worked out so far. Just need time to get back to it someday here.
 
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