I have these lovely walnut crotch medallions with one end flat where the tree was sawn. If the bottom flats were jointed, two of the pieces would make a lovely bookmatch about five feet long that would be more lovely still if cut into an oval that roughly followed the shapes of the medallions. What a lovely coffee table top they would make.
The problem of course is that at the center of the table would be an end-grain butt joint.
Would the use of butterfly joints on the underside be effective in holding the joint tightly toghther (assuming effective support from the legs etc? I would want the table to refined in appearance, so gaping cracks and such wold not be acceptable.
Replies
Hi Joe,
You could always join the two end grain pieces with some sort of tenon , or several heafty butterflies. Maybe leave a small gap between the two pieces as a design element.
Bob
joint
How about a long, industrial-strength spline?
Butterfly, tennon or spline
Both the spline and the tennon ideas have merit.
This is beyond anything I have done, so I can't help but worry, though, because of the width of the table. There would be the normal wood movement that would tend towards cracking if a spline or tennon were too wide. That would mean fastening in the middle only, like a breadboard end, which might mean that the joint would open disagreeably.
That is why I wondered if hidden butterfly keys would work better by keeping the joint tight and moving with the wood. Or am I fooling myself? Could I get by with only a spline or tennon? Of would the butterflies themselves actually work?
Not arguing, mind, just thinking out loud.
Joe
thinking
Thinking is good. I'm not sure which approach would be best, either. My guess would be, however, that one or more butterflies on the bottom side wouldn't suffice to keep it together, if it wants to move. I think you'd need to examine the grain pattern and direction to estimate how it might move, and then decide on that basis. But, grain pattern and direction alone may not be sufficient. There may be hidden internal stresses that aren't telegraphed in the grain.
Strategy
The strategy to make the spline is to make the grain run the same direction as the two halves. With crotches, the grain should be running approximately 90 degrees to the joint.
If the spline is to be 1/2" th x 2" long x 24" long (all guesses), the grain needs to run the 2" direction. This bridges the joint with long grain, and the spliine will move in width with the two halves. The spline could also be several pieces to make the width - this is not important.
This arrangement joins/glues long grain to long grain, despite the end grain. Yellow glues will work well. Epoxy will bond end grain, but requires little/no clamping and cures rigid.
It would be prudent to have some support under the two halves to help the spline do its job.
Dave S, Acorn Woodworks
Strategy
Ralph and David:
This sounds better and better, and makes good sense. A coupole of followup questions:
1) Are you saying that epoxy is too rigid?
2) It is pretty hard to say just where the grain runs with these pieces as they are crotch, but the prepponderance of it would mate up with the 90 degree spline just as you say. Will the crazy reversals and upendings of the rest of the board cause problems?
Joe
Assuming....
Assuming the wood has been properly dried and is used in such a way as to allow it to move with the normal variations in RH, all should be fine.
Some support under at the joint area would be strongly advised, but it need not be massive or even visible to the avreage viewer. I have always said that if you are in a postion to see something under a tabletop, you should be doing something other than inspecting the underside of said table top.
I think I would stay with yellow glue, as the epoxy is messy and you don't relly need to bond the end grain. The more I use epoxy, the less I clamp it. Since it is gap filling, I find it actually likes/needs a gap to perform at its best. I like to turn those clamps, so epoxy gets squeezed out.
Dave S
glue and support
Dave:
The wood was air dried for a bit over a year, then kiln finished. Since then it has been in covered non a/c storage for a couple of years, but will be acclimated to my shop before being cut.
I can put plentyof support under the joint. This will be an oval coffee table with legs and supports springing from a flattened fluted urn form. Hterefore, I can make the supports into design elements
J
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