I made a fine jewelry chest on long legs a couple of years ago from cherry and walnut. It’s been sitting in galleries since then, and when I took a look at it the other day, I was dismayed to feel the joint surfaces no longer matching up where the sides of the box meet the legs. This is a cross-grain mortise and tenon joint, and the widest part of the side at the joint is about 4″, so seasonal movement is evidently the cause. You can’t easily see this, but I can feel it when I run my finger under the curve of the joint, with the sharp edge catching my finger in a most unpleasant way. (see picture on homepage www.treeheart.com)
I was hoping there was some way in the future to avoid such a problem in small pieces like this. Obviously, if the grain was not crossed, that would help, but then the side of the box would be even more of an issue in other respects when it expanded and contracted. How did Sam Maloof make his joints not do this?
Thanks for your input.
Don W.
Replies
Don,
Nice work, I enjoyed touring through your site, the drums especially must be fun to make.
I think that two things are contributing to the problem: You are using two species of wood which respond differently to changes in relative humidity, combined with the fact that some of the wood at the joint interface is flat sawn and some is quarter sawn. The flat sawn wood will change less in thickness than the quarter sawn for the same amount of moisture change.
The two factors combined mean that the panels will at times be a few hundredths thicker or thinner than the legs they key into, making it impossible to keep the surfaces of the joint level at different levels of relative humidity.
One solution is to create a step at the joint so that the legs are always distinctly above the face of the panel so minor shifts won't be detected.
A second fix is to run a groove at the joint line so the two surfaces don't touch at the surface where the hand could sense the slight height difference, this is why "v" grooves are sometimes run in flooring and paneling.
Hope this helps, John W.
P.S. I thought you were talking about the wide faces of the sides where they blend into the sides of the legs not staying exactly flush, but reading the third response, and then rereading your note, I guess that maybe you are talking about the top and/or bottom edges of the sides not staying flush where they join the leg.
If that is the case, then of course you are dealing with wood expanding across the grain but basically not moving at all parallel with the grain. The fix is still the same, the wood has to move so you need to design the piece so the movement isn't noticed. The only alternative is to make the sides of the box as small floating panels but that would completely change the design.
Edited 12/23/2004 5:11 pm ET by JohnW
Edited 12/23/2004 6:20 pm ET by JohnW
Thanks John, for your thoughful post. The drums are fun - plus I get to play them. The big community drums are really something - window rattling sound.
I have used the step approach on tables with success, but I couldn't see a good way to do this with the wrap-around curve. I probably just have to change my design concept, which is mostly seat-of-the-pants style. A little planning would help, but I generally finish shaping the parts after assembly, making some techniques difficult to implement. I'm too attached to that smooth curve transition from leg to apron.Since I live in a high humidity area of southern illinois, the air conditioned galleries do put the wood thru some serious changes.
Don
Very nice job. I assume that you want to stick with solid wood construction, but if you didn't, you could use a ply veneer as your apron piece. I think you will always have this problem in solids and more pronounced with a wider apron. I would glue the bottom 2" or so of the tenon, so the curve always stays smooth, and leave the top to float [ possibly using dowels to peg it in place ] If I was building in high humidity I would make the apron flush to the top of the leg, and if in low humidity I would leave it 1/8 or so below flush. I would also not run the groove for the tenon all the way to the top of the leg to hide the expansion more. Nice website by the way.
Peter, thanks for your ideas. I guess that expansion has got to go somewhere - the nature of life. The veneer idea would be difficult on all that curvy surface. But controlling the place of expansion has merit. I made a tall skinny table that solved the problem by running the apron grain vertically, and there were no critical areas where the expansion around the perimeter would show, since the table top overhung by an inch. Small boxes are unforgiving of small changes in size. Wood's a challenge, for sure.
Don
I don't see it as a problem.
This forum post is now archived. Commenting has been disabled