First of all, not the kind Jerry Seinfeld talked about… A couple years ago, I made a beautiful chess table. It is probably the closest thing I have ever made to “fine” furniture. I made the table in Salt Lake City where the humidity is remarkably low. I have since spent two years in Indiana where humidity is high and am now in San Diego near the coast where the humidity is moderate, but can fluctuate significantly. I used three woods in the construction, walnut, maple, and zebrawood.
The chess board is walnut and maple and the border is zebrawood joined to the board by tongue and groove. The two zebrawood boards along the side with exposed endgrain is now 1/16th to 1/8th of an inch shorter than the other side boards. Similarly, walnut stretchers that run between maple legs, joined by mortise and tenon joints, are pulling out. The separation on these joints is also about a 1/16th of an inch on either side.
Two questions for the forum. First, can and how do I fix these joints?
I imagine that wherever two woods with varying shrinkage/expansion properties are joined there can be significant issues with problems like the ones I have experienced. This brings me to my second question. What is the best way to design around these complications? I’d really not like to repeat this problem.
Thanks.
Replies
I'm having trouble visualizing how the piece is assembled, but some background on wood movement.
Wood expands and shrinks across its width and thickness, almost none along its length. Wood moves more in the direction along the growth rings (tangential) and less perpendicular to the growth rings (radial). Movement can be calculated as a factor times the dimension in inches (width or thickness).
If the chessboard is made of a number of full thickness alternating squares of maple and walnut, each square will move across its width but not along its length. If the grain in all the squares is oriented in the same direction, the overall board will move across its width but not along its length. If the squares alternate direction, movement would try to break the glue joints but may or may not be sufficient to do so. Many boards are made with veneer squares on ply or MDF substrate to avoid movement issue.
If the collection of squares is picture framed or wrapped with a solid border, and the squares all run in the same direction, there will be conflict between the squares with grain running in one direction, and the cross grain border, which will not move along its length. There will not be a conflict between the squares and the parallel grain border strips.
If the board in turn is mounted on an apron-and-leg base like on a coffee or hall table, provision must be made to allow the top to move independent of the base. This allowance can be in many forms, including figure 8's, wood buttons, screws in slots, . . . If the top were veneer on sheet good it would not move appreciably and could be rigidly attached to the base with less chance of conflict.
Hope this helps and I haven't made any misstatements.
Pictures
Can you post some pictures? It sounds like a classic case of contruction without regard to the natural expansion/contracton of wood with changes in relative humidity.
Whether or not it can be salvages would be much easier to determine if we can see how it is constructed and how it is damaged.
In general, the correct construction technique to make your checkerboard field is to use contrasting thin wood veneer (max 1/8" thick) glued to plywood or other composition material substrate. Composition materials are not subject to movement due to changes in humidity and you do not have conflicting expansion/contraction issues. Solid wood surruound by an edge grain border are destined to fail.
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