So will they flatten?

[phil (admin)]

About a year ago, I glued-up some walnut tops a little over 24" square (3/4" thick).  They were flat when I was done.

I sat them aside, they've had good ventilation on both sides, but they've cupped about 3/16 along the width.

I can pull the cups out of them when I attach them to the tables, but doing so will probably require me using the figure-eight fasteners like these:

http://www.rockler.com/desk-top-fasteners

Instead of the type to which I'm accustomed:

http://www.rockler.com/table-top-fasteners

I'm afraid the 2nd ones may cause the kerf into which they're gripping to crack.

I've never used the figure-eight fasteners, is there a good trick for counter-sinking these things?

I've clamped on of the tops flat for now.  I suspect when I unclamp it tomorrow it will spring back with enthusiasm.  However, if the cup seems more pliable I might try the 2nd type of fastener.

Any experiences with cupped tops?

[ORBlackFZ1]

Phil:

I have had the same situation with a 12" x 18" piece of 1" cherry strips that I had glued up.  When I picked up the piece 6 months later it was cupped about 1/4".  I decided to change the storage position and checked it about a month later and it was completely flat again.  I had been storing my glue-up on top of some other lumber.   The moisture was getting to the top side and expanding that side.  The moisture was not getting to the underside.  My moisture meter helped me determine what was happening. 

You might want to experiment with a different storage position before you change your table holders.

If you do change your holders, I would think you could countersink the table holders by using two different size forstner bits and then cleaning it up with a sharp small wood chisel.

[phil (admin)]

In my case I had the tops leaning against other stuff, so air was able to circulate around pretty evening.  But perhaps the air movement wasn't as even as I thought.

I'll experiment with countersinking/chiseling the figure-eight things.  I have to order some if I'm going to use them.  The newer ones at Rockler and Woodcraft are apparently stamped and bend easily.  Looks like Lee Valley still carries the good stuff.

Thanks for the feedback!

[tommitytomtom]

If the tops were leaning against something, which way was the grain orientation ? Vertical or horizontal ? Leaning wood with the grain horizontal to the floor could cause the tops to cup. Is this quarter sawn wood ? It would be less likely than if not. We all know temperature and humidity and grain orientation makes wood move. I don't think the metal clips should be relied upon to correct the cupping. It seems to me that would be forcing the top to bend rather than the clips holding the top to the frame.

[phil (admin)]

If the tops were leaning against something, which way was the grain orientation ? Vertical or horizontal ? Leaning wood with the grain horizontal to the floor could cause the tops to cup. Is this quarter sawn wood ? It would be less likely than if not. We all know temperature and humidity and grain orientation makes wood move. I don't think the metal clips should be relied upon to correct the cupping. It seems to me that would be forcing the top to bend rather than the clips holding the top to the frame.

That is a good question, I don't know how the grain was oriented when the panels were resting.

Instead of using the figure-eight clips, I decided to use pocket screws through the apron and into the top.  For the screws along the center of the end grain, I kept the screws snug.  For the others (where wood movement may occur) I didn't snug the screws all the way, and enlarged the holes a bit.

This allowed me to flatten the tops nicely.

I did look at the tops on the tables I'm replacing, which were 20" square solid walnut 3/4" thick.  Sure enough, over the last year or so, they have moved quite a bit, too.  The Z-clips I used to secure those are strained in a spot or two.

Oh and no, this wood isn't quarter-sawn.

Oh and the board grain orientation (the rings) are reversed one board to the next.  Now, I didn't do this on purpose, I arranged the boards so they've have the most pleasing appearance.  It just worked out this way.