Which is stronger?

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For those of you who don't get abpw:
Rough sketch of chair leg and rail (legs angled 7 degrees from vertical)
I know what I _think_, but which "floating tenon" joint to YOU _know_ to be stronger and why?
http://www.e-woodshop.net/images/TenonTrial.JPG
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B is stronger because there is enough material strength in the mortise of the rail.

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Actually, with "A" there appears to be more "material" for "strength" at the top of the rail/stretcher, where you (not "you" personally, but a non-engineer for sure) would think it would do the most good:
http://www.e-woodshop.net/images/TenonTrial3.JPG
... and would an 1/8" at the bottom make that much difference?
hmmm.... ;)
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Swingman wrote:

I would go with "B". Does it need to be floating tenon? It would be slightly stronger if you use a real tenon. For a chair this could be significant.
Chris
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"Chris Friesen" wrote in message

While I tend to agree on the surface, that's actually been proven to not make much difference, if any, and certainly a "real" _angled_ tenon could be much less strong depending upon the grain of the particular piece.
The jury is still out ... :)
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Swingman wrote:

"Not much difference" isn't the same as "no difference". Your point about the angled "real" tenon is well-taken.

There's only one solution. Build a few of each, test to destruction, and write it up for FWW.
Chris
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Swingman wrote: > "Chris Friesen" wrote in message > > >>I would go with "B".
I'm to lazy to do it for you but if you calculate the section modulus of each joint, you'll find "B" is stronger.
S = M/Z
S = Stress M = Bending Moment Z = Section Modulus
Z = I/d
I = Moment of Inertia d = Distance from centroid to outermost fiber.
I (for a retangle) = bh^3/12 = 1/2ad^2
b = base h = height a = area d = distance from center of area to center of bending moment.
Any decent strength text will give you the formula for a circle.
(Dredged from my memory from all those strength of materials classes taken so long ago.)
Have fun.
Lew
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"Chris Friesen" wrote in message

The quote was "not much difference, if any" ... and a lot of folks, like the beadlock folks, David Marks, and Lon Schleining (sp) of FWW, to name a few, seem ready to swear to/by the "if any" part.
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"Chris Friesen" wrote in message

The chair was designed a hundred years ago ... it's time now to suss out the possibility of new/different joinery methods for a "production" run that will hopefully last the same length of time.
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Swingman wrote:

I tried to cancel that post, but I guess it got through anyway. The racking resistance with shoulders will be fine (possibly better), as long as the tenon doesn't pull out or the shoulders fail.

"A" has the advantage that the mortices are at right angles to the ends, making it simpler to mill.
If you're looking at a "production" run, it really might be worth testing both designs to failure.
Chris
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"Chris Friesen" wrote in message

Bingo ... and therein lies the reason for the question. :)

Yep ... a limited production run, in a space limited shop (but with plenty between the ears, some would say), by a time limited wooddorker, wanting to test the limits of angled "loose tenon" joinery.
Actually, both are doable, and while I've already cracked the "B" methodology with a homemade jig, "A" is easier, and much, much more "precise" (at least without that JDS Multi-router I keep threatening to buy).
... and in joinery, precision often trumps even a tiny bit sloppy, with regard to strength.
Thanks for the input, Chris.
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On Mon, 19 Jun 2006 13:06:25 -0600, Chris Friesen

I don't think so. With B the rail would be clamped vertically and the mortise made vertically, the angle is irrelevant. To do A you've have to hold the rail at an angle. The leg is maybe harder depending how the mortise is made. Not very difficult to tilt the table on a drill press.
And I cast another vote for B being stronger. You've got more uninterrupted long grain on the end of the rail.
-Leuf
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"Leuf" wrote in message

<snip>
If you precut the rail/stretcher end to the required angle (7 degrees in this case), they (leg and rail) are both easy, 90 degree plunges.
"B" is trickier, less precise IME, and requires a much longer bit.
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With a router you mean? How does one keep a router on the tiny surface of the end of the rail?
-Leuf
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wrote:

He has a cool jig to clamp to the rail that holds the router.
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On Mon, 19 Jun 2006 23:10:09 GMT, "Leon"

Yeah, but.. it clamps to the sides of the rail right? So what difference does it make what angle the end is at, other than that if you don't want the mortice parallel to the sides it has to be able to compensate for the angle?
-Leuf
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"Leuf" wrote in message "Swingman" wrote:

Good question. I've put some pictures up for you.
Go to the url below and scroll down to "Router Mortising Jigs" and you'll see the simple jig that allows you to do this:
http://www.e-woodshop.net/Jigs.htm
Let me know if you have any questions.
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OK Swingman, I have to make these remarks.
I have worked in various communication capacities and have had to evaluate marketing materials and corporate communications. I had to constantly fight the artsy fartsy graphic designers who can take any simple communication task and turn it into a psychedelic nightmare. I remember when a newsletter was a page or two of typewritten information that you could use.
Your website is a marvel in simplicity. Both in terms of design and communication. You use pictures to illustrate what you are talking about. You give short, concise messages with the pictures. And you do so in a warm, folksy manner that is such a refreshing alternative to the marketing centric styles of so many other websites.
And it chronicles a guy who has a simple, small shop. There is no big warehouse or commercial shop here. It gives information freely to ordinary folks who want to create or expand a home workshop. I have your website in my favorites list. And I recommend your site to others.
Just wanna say, good job sir. If more folks did such a good job as you with their website, the web would be much more enjoyable (and educational). It makes the whole putting together a shop thing more do-able. It is a pleasure to peruse your website.
Now I gotta go back to being my usual curmudgeon self.
Lee
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"Lee Michaels" wrote in message

... and you sir, have to be one of the most intelligent folks on the planet! ;)
Thanks for the kind words ... I'll be blushing for the next week or two.
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As you should ...your one of the guys whom make the wReck a "must read" with my morning coffee.....Thanks Rod
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