Tenons on a wide board (again)

H

HSteier

Well-known member
Earlier this year there was a long interesting exchange about tenoning wide boards such as those on Queen Anne lowboy sides.  Many of these boards have cracked on old pieces because of wood expansion/contraction that was limited by the tenons being glued fast into the legs. But I wonder would this still be a problem in today's indoor environment. I know that there are theories that cracking occurred only after central heating became prevalent and that central heating dried the wood more and caused more shrinkage and more cracking. But I'm always skeptical of "conventional wisdom".
I have a buffet I made 8 years ago with an 18" wide walnut top. There are breadboard ends and they are tenoned and glued. There has been no shrinkage/cracking/loosening of the joint in this time. I didn't do anything special to seal the wood. The piece is shellacked.
Does anyone else have any direct experience with this. Was I just lucky with the above piece?  I remember Dennis Bork's comments  about cracking after pre-compression. Did the cracking occur because of the precompression or because the tenons weren't floated?
What about the backs of these pieces?  Were they pegged and then the cracking was just accepted because it wasn't seen?

Howard Steier
 
Howard,
Do you have a somewhat climate controlled environment at your house? A year around consistency in temperature and humidity would minimize wood movement. 
Mike
 
I live in Virginia Beach where it's very humid year round except in the summer when it's horribly humid. I have central air conditioning and heat pump/electric back up heat. That's more or less the standard in this area.  There is no attempt at humidity control. But that's my point. Is this enough "climate control" so that we don't have to worry as much about shrinking/cracking?

Howard Steier
 
Howard,
That would be my guess, AC removes a lot of humidity. I live in Minnesota where we go from tropical in the summer  to -30 degrees F. in the winter.  Without AC The humidity swings are huge indoors.
Make yourself a  humidity gauge. I made one of unfinished poplar about 1/2 " thick 6" long (with grain) and about 16" wide (across grain). On one end I attached a 16" long board about 1 1/2" wide running across the grain of the wide board. Make marks on it once a month to chart what happens. If you keep one in your shop it will help you keep track of where your lumber is in the "cycle".
Mike
 
One technique to minimize the possibility of cracking is outlined in Jeff Greene's "18th Century American Furniture" book.

Clamp the wide panel tightly across the grain using cauls. Then, with the clamps still on, glue the panel to the legs or whatever. After the glue is dry, release the cross clamps.

Clamping across the grain compresses the grain, artificially shrinking the grain. Releasing the clamps after the glue up releases the compression, actually stressing the joint in expansion. That way, when the panel shrinks, this stress is released first, meaning that it would have to shrink a great deal before being able to crack.

With stable wood and normal household moisture swings, you should be well protected.

Hope this helps,

Ralph
 
If you look back in this section to the original thread "Tenons on a wide board" from Feb 2007, this method of precompression was mentioned. Dennis Bork, who is a professional cabinetmaker, said he used this technique once with disatrous results (subsequent cracking of the board). So I ask has anyone used precompression with good results or is this another "conventional wisdom" or theory.?

Howard Steier
 
Ralph,

The method you stated from J. Greene's book is ecactly what I tried with disatrous results.  Remember, the boards can crack from expansion as well as shrinking.  The customer was very upset so I had to replace the sides of his lowboy with floating sides.  Do whatever method you want but I would rather be safe than sorry later. Just because someone writes a book does not mean that all the theories are correct and workable.

It is always interesting to go to a past customer's house and see an item I made years ago.  I will look at the underside to see if there has been any wood movement of the top.  Most all the times there will be a stained/unstained line where the top meets the apron or frame due to movement.  This is even seen on tops of Pembroke tables only 18" wide.
I'm then glad I used floating tops and floating case sides.

Dennis Bork
Antiquity Period Designs, Ltd.
 
I too prefer floating sides whenever possible, but when faithfully reproducing a period piece, we are not always free to do as we wish.

I HAVE used the compression method with great success. Using older wood is almost required however.

I don't believe the method is at fault, but probably the material. Wood that was harvested 200 years ago, ususally took hundreds of years to grow, and the pores were amazingly tight. Old red oak is not the same wood as modern red oak and does not have the same mechanical characteristics.

So I posit that the old growth woods expand and contract less than woods grown rapidly today.

Ralph
 
Pam,

For case sides I mean the sides of a lowboy/highboy.  I glue and pin one tenon and float the other two.

Dennis Bork
 
Ralph,

I had a 150 year old cherry secretary.  The 20" wide one board sides moved 1/4" between summer and winter.

I still would never use the compression method on new lumber.  My old boss would tell me, "make the job so it does not come back for repair".

Dennis Bork
 
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