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I'm building an outdoor table and the table top is being assembled using dominos and glue. It's 6' long and I'm using pipe clamps to clamp the long side together while the glue dries.

As I was tightening the clamps in order to bring the joints together tightly, I noticed that the entire table was cupping due to the pressure. I reduced the pressure once I got it together and it seems to have glued up well, but ideally I would be able to keep the pressure on while the glue dries.

What are some strategies I can use to prevent this from occurring when clamping really long and thin (3/4") components?

Since a picture always helps, I am clamping the length of this table top (pieces just placed for layout here): Table top

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The 2 things I can think of that help.

  1. rotating which face is 'up' strip by strip.

  2. for things as thin as what you are dealing with what will make more difference is alternating your pipe clamps between 'top/front' and 'bottom/rear'It is a little more difficult set up, but if you have pipe clamps you can lay out on a table put your glued up pieces on them, start tightening them down and in between the ones on the table lay and tighten others on the top face. Get them all snug then go ahead and tighten them down, if you have more than 3 gluings going on at once (say you are gluing 10 strips on one clamping, then you still need to take care and not tighten them down too hard or you can still get binding and bending.

    enter image description here

  3. Oh and a 3rd. Using 'guides' (I know there is a better name) clamping straight boards across the face of your glue job to keep things flat. You will have to go back and forth in tightening or if you tighten the bar clamps to soon, you might get cupping and if you tighten the face boards to much you won't be able to 'squish' the face together.

    enter image description here

  • It's a table with 5" wide slats (3/4" thick), and there are 6 of them per section and 2 sections. So I had to clamp all 6 at once on one side, which was only 3' long so no cupping problem, but when I did the other half of the table which made the 6' length, it started to cup – Steven Aug 27 '15 at 15:57
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    'Caul' is the term you're looking for. ;) – TX Turner Aug 27 '15 at 16:48
  • @TXTurner yes, yes it is! – bowlturner Aug 27 '15 at 16:50

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