Replies

1. 
   YesMaam27577 | Dec 15, 2008 10:51pm | #1

   I've never tried it but......

   It seems to me that the strength of the joint would be just as good as a "normal" tenon.

   But there is the issue of perfect haunch placement. In general, the mortises are going to be just a bit deeper than what is needed for the tenon. And, haunched tenons are, in general, haunched so that all gaps are filled in the finished joint. Think of them as being part of a cope-and-stick joint, but that they go deeper.

   In this respect, the placement of a loose haunch (or the haunched portion of a loose tenon) becomes critical. How would this placement issue be resolved?

   Politics is the antithesis of problem solving.
2. 
   RalphBarker | Dec 16, 2008 12:47am | #2

   To me, the strength of a tenon is that it uses a long segment of long grain, supported by the rest of the board. A loose tenon, in contrast, is more like a doweled joint, where the strength relies on the break-out strength of the surrounding wood only, with almost no long-grain strength.

   Haunching the loose tenon might increase the glue surface area, but I can't see it as being as strong as a "real" tenon.

1. 
   Rich14 | Dec 16, 2008 03:01am | #4

   Ralph,A "loose" tenon, while theoretically weaker than a true tenon, is for all practical furniture building (any conceivable stress the joints could experience in normal use) just as strong.The long grain of the tenon itself is glued to the long grain of the tenon piece (in its "mortise" there, but using that word creates confusion). That glue joint is actually stronger than the surrounding wood. Whether the wood in the tenon piece surrounding the glued tenon is weaker than the wood of a solid tenon/tenon piece is debatable.It may be weaker in tests to destruction. But such stress would literally destroy the furniture long before the joint failed. So what if a real M&T survives under conditions where the loose type fails if the piece would otherwise be smashed?Destructive tests don't really indicate how systems perform in real world situations. Stress below that point results in similar performance by real M&T joints and floating type.The tenon to mortise joint in the mortise piece is the same in both types.Rich

1. 
   RalphBarker | Dec 16, 2008 05:26am | #5

   Rich, I'd agree that "normal" stress on a piece of furniture is generally limited to the weight of the piece and its contents. Most items never see any sort of lateral stress that might tax the joints. If I were designing and building something like a workbench that *does* experience lateral stresses, I'd probably lean toward conventional M&T joints (hefty ones at that), though.

1. 
   Rich14 | Dec 16, 2008 05:35am | #6

   Ralph,Normal stress on furniture includes far more than the static conditions you describe. It entails moving, pushing, lifting, people standing on it, storage upside down, on its side, etc. Most normally-constructed furniture can withstand stresses far exceeding those.Tests to failure that can show the differences between otherwise robust but different joint construction goes beyond those limits.My point is that well done "floating" M&T construction can easily result in high-quality joints and furniture that can far outlast its maker.Rich

2. 
   ring | Dec 16, 2008 10:52am | #7

   Loose tenons are, for all practical purposes, equal in strength to integral tenons. The lab tests I've seen, as well as experience, show no significant differences. The choice is much more a matter of what your equipment can reliably produce. A close-fitting loose tenon is infinitely preferable to a mediocre integral tenon.
   David Ring

   http://www.touchwood.co.il/?id=1&lang=e

3. 
   digger007 | Dec 16, 2008 02:13am | #3

   Now what if you made the tenon fit tight with the grain running the same direction (long) with the grain of the rail or whatever it might be.  Also I don't know if squaring the edges up would do anything either. But I guess your still relying on the glue to hold the entire tenon in place.  I don't know, might be worth a try.  Great comments thus far!!