splitting table tops
I have been having trouble with table tops splitting sometimes months after they are done. The most troublesome of course are the ones with a frame around them. I have been gluing them together and using a cleat to glue then to the apron. I recently bought a moisture meter and am wondering how low it should read before I begin to glue up. I also bought some of set clips and will try them to attach to the apron. Any other obvious ideas? Help…. –Eric
Ericl, from what I read you are gluing the tops right to the frame, thereby not allowing the movement of the top. Make sure you use clips to hold your top so it will allow movement.
and using a cleat to glue then to the apron.
If you are in fact gluing the top to the apron, then that is one of the problems. Use only the cleats, and no glue. This allows the top to float on the apron. If you glue the top to the apron, you will be gluing a cross-grain joint.
Unless you're the lead dog, the view just never changes.
You cannot put a frame around a glued up table top! Research breadboard ends for more info. You can only put a plywood, MDF, etc in a restrictive frame due to expansion, contraction issues. A door panel allows for this movement. Rule of thumb is typically 7-8% for kiln dried wood. Obviously you don't want to glue a 7% board to a 12% board. Hoadley's book on Understanding Wood is well worth the money. Cheaper to do the research before than to research after the problem. Joyce's book on Furniture Making gives fundamental rules on basic furniture construction techniques. Those two books should give you the answers you seek and prevent future problems.
The others have pinpointed your problem ... you're not allowing the top to expand and contract with moisture changes.
What I do, in addition to using shop-made wooden buttons to hold the top down (the buttons have a tongue which goes into a kerf made by my biscuit jointer, and the button's tongue can move into and out of the kerf) is to use a dowel at the mid point of the ends (in the middle of the apron) to register the top. The dowels protrude up from the apron about 3/8th of an inch and are not glued to the top. They're for registration only. Note that my grain runs the long way, so I'm adding dowels in the long grain, and there isn't movement in this direction. If I were to make a top with the grain running the short direction I'd change my dowel location likewise.
I simply always want my tops to be centered on the base, and the above does just that. (I use one dowel on one end, and two dowels, an inch apart on the other, so that the top goes on only one way.)
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