Fixing a table

I had an interesting little project this week. My client bought a solid mahogany dinning table 20 years ago in the Netherlands. It is a beautiful piece, and well constructed save one thing. Seven years ago when the table was shipped over seas to Indiana, the extreme changes in humidity caused the wide boards of the table top to swell and shrink, breaking the glue joints and creating gaps which during the winter exceed 1/8" wide! It seems humidity changes are not a problem in the Netherlands, so the table was built without allowance for expansion and contraction of the wood.

The solution was fairly simple. First, re-glue the joints using biscuits to ensure strength (previously they were simply butt-jointed and glued). Second, expand some of the screw holes into slots to allow movement of the screws as the top expands and contracts. Third, replace some of the screws holes with slotted hold-down blocks. (Fortunately, the skirt had not been glued to the top, that would have been a very bad mistake in construction!)

Here's how the table looked when I brought it into my shop (this is one of four pieces which I worked on)


Here's one of the screw holes on the underside supports before I modified it.


And after modification


This is the jig I made to lengthen the counter-sink bevel using a router and v-grooving bit. Then I used a drill press to expand the through hole. Perhaps not all that elegant, but simple and effective.

On the ends, where the slots would need to run perpendicular to the direction of the skirt, I added these blocks and removed the existing screws. The blocks hold the top tight to the skirt while the slots allow the screws to move when the tops expands.

I should note that even though the slots will allow the screws to move, they are tight enough to not move by hand, it will take a lot of force to move the screws, but hopefully less than it takes to break the glue joint.