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

--
www.e-woodshop.net
Last update: 5/6/06

B is stronger because there is enough material strength in the mortise of
the rail.

"Swingman" wrote in message
...
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

--
www.e-woodshop.net
Last update: 5/6/06

Swingman wrote:

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

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

"Chris Friesen" wrote in message

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.

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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Last update: 5/6/06

"Frank Arthur" wrote in message
.. .
B is stronger because there is enough material strength in the mortise of
the rail.

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....

--
www.e-woodshop.net
Last update: 5/6/06

Swingman wrote:

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.

"Not much" difference is not "no difference". I know I tend to lean
back in chairs...so I'm partial to ones that are as strong as possible.

Certainly, and angled "real" tenon could be a problem.

As for the angled loose tenon...how deep were you planning on making the
mortices? There's no scale on the drawings.

Finally, what about leaving the rail at full dimensions? Are the legs
thick enough? Your resistance to racking increases with the third power
of the vertical height of the rail, so a small increase can pay off.

Chris

Swingman wrote:

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.

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

The jury is still out ...

There's only one solution. Build a few of each, test to destruction,
and write it up for FWW.

Chris

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

Swingman wrote:
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


In "A" a considerable portion of the sides of the mortise
in the stretcher is short-grained and prone to splitting.

"B" does not have that flaw. "B" is stronger.

--

FF

"Chris Friesen" wrote in message
Swingman wrote:

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.

"Not much" difference is not "no difference".

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.


--
www.e-woodshop.net
Last update: 5/6/06

"Chris Friesen" wrote in message

Finally, what about leaving the rail at full dimensions? Are the legs
thick enough? Your resistance to racking increases with the third power
of the vertical height of the rail, so a small increase can pay off.

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.

--
www.e-woodshop.net
Last update: 5/6/06

Swingman wrote:
"Chris Friesen" wrote in message


Finally, what about leaving the rail at full dimensions? Are the legs
thick enough? Your resistance to racking increases with the third power
of the vertical height of the rail, so a small increase can pay off.

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.

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.

"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

wrote in message

In "A" a considerable portion of the sides of the mortise
in the stretcher is short-grained and prone to splitting.

"B" does not have that flaw. "B" is stronger.

post hoc, ergo propter hoc? ... a 7 degree difference in grain direction
would not be uncommon in any angled tenon.

But I tend to agree with you ... grain direction appears to be a key factor.

--
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Last update: 5/6/06

"Chris Friesen" wrote in message

"A" has the advantage that the mortices are at right angles to the ends,
making it simpler to mill.

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

If you're looking at a "production" run, it really might be worth
testing both designs to failure.

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.

--
www.e-woodshop.net
Last update: 5/6/06

On Mon, 19 Jun 2006 13:06:25 -0600, Chris Friesen
wrote:

"A" has the advantage that the mortices are at right angles to the ends,
making it simpler to mill.

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

"Leuf" wrote in message

To do A you've have to hold the rail at an angle.

snip

The leg is maybe harder depending how the mortise is made.

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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Last update: 5/6/06

On Mon, 19 Jun 2006 14:53:03 -0500, "Swingman" wrote:


"Leuf" wrote in message

To do A you've have to hold the rail at an angle.

snip

The leg is maybe harder depending how the mortise is made.

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.

With a router you mean? How does one keep a router on the tiny
surface of the end of the rail?


-Leuf

"Leuf" wrote in message
...
On Mon, 19 Jun 2006 14:53:03 -0500, "Swingman" wrote:




With a router you mean? How does one keep a router on the tiny
surface of the end of the rail?


He has a cool jig to clamp to the rail that holds the router.

On Mon, 19 Jun 2006 10:57:00 -0500, "Swingman" wrote:

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


I'm not really for either as they stand but might go with a variation
of "B", in what I'd call a double secret probation - uhh, wait a
minute - a "Double Secret Wedged Tenon".

Usually a wedged tenon is a show joint but you can do a secret one by
undercutting the edges of your mortises by the seven degrees described
to form a kind of keystone shaped hollow.

Cut your wedges to fill that seven degree void once they bottom out on
the mortise. Cut the appropriate slots in the tenon. Butter the
tenon and the wedges up and insert the wedges just barely. Drive the
loose tenon home to form a dovetail within the keystoned void. Prep
the other end of the tenon the same way and clamp her up.

You'll wind up with opposing dovetails.

Dat sumbitch be strong.




Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

"Tom Watson" wrote in message

I'm not really for either as they stand but might go with a variation
of "B", in what I'd call a double secret probation - uhh, wait a
minute - a "Double Secret Wedged Tenon".

Usually a wedged tenon is a show joint but you can do a secret one by
undercutting the edges of your mortises by the seven degrees described
to form a kind of keystone shaped hollow.

Cut your wedges to fill that seven degree void once they bottom out on
the mortise. Cut the appropriate slots in the tenon. Butter the
tenon and the wedges up and insert the wedges just barely. Drive the
loose tenon home to form a dovetail within the keystoned void. Prep
the other end of the tenon the same way and clamp her up.

You'll wind up with opposing dovetails.

Dat sumbitch be strong.

I reckon ... excellent, vivid description. Thanks, Tom.

--
www.e-woodshop.net
Last update: 5/6/06

"Swingman" wrote in message
...
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

--
www.e-woodshop.net
Last update: 5/6/06

My credentials: degree in mechanical engineering with a specialization in
strength of materials. Formerly a licensed professional engineer in the
state of Illinois. Based on the rough drawing, if you made 10 of these
joints each way and tested them to failure, I'm not sure you could measure a
statiscally-meaningful difference between the two. Now, I haven't spent all
night thinking about it, so if someone can make a persuasive argument to the
contrary, I'm open. So with that said, offhand I'd go with the one you find
easier to machine.

todd

On Mon, 19 Jun 2006 20:19:39 -0500, "Swingman" wrote:

"Tom Watson" wrote in message

I'm not really for either as they stand but might go with a variation
of "B", in what I'd call a double secret probation - uhh, wait a
minute - a "Double Secret Wedged Tenon".

Usually a wedged tenon is a show joint but you can do a secret one by
undercutting the edges of your mortises by the seven degrees described
to form a kind of keystone shaped hollow.

Cut your wedges to fill that seven degree void once they bottom out on
the mortise. Cut the appropriate slots in the tenon. Butter the
tenon and the wedges up and insert the wedges just barely. Drive the
loose tenon home to form a dovetail within the keystoned void. Prep
the other end of the tenon the same way and clamp her up.

You'll wind up with opposing dovetails.

Dat sumbitch be strong.

I reckon ... excellent, vivid description. Thanks, Tom.


Ya know, Swing, like most joints, it prolly talks harder than it cuts.

I don't think it will slow you down any in production once you get
through the Goldilocks process of, "Too Tight, Too Loose, "Just
Right".

All new joints are a process until you get to the point of, "Fire For
Effect".

I believe it would be a damned strong joint, with little extra time
involved, once the jigging was perfected.

It sounds like you are trying to use a router.

I'm not big on round-shouldered joints, regardless of the gluing
surface presented.

I'd use a morticer and be done with it.

I like the lock of the right angled shoulder, and with a joint that is
not haunched, I would particularly look for some right angles in the
joinery.

Just my opinion.

As always YMMV.






Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

On Mon, 19 Jun 2006 23:10:09 GMT, "Leon"
wrote:


"Leuf" wrote in message
.. .
On Mon, 19 Jun 2006 14:53:03 -0500, "Swingman" wrote:




With a router you mean? How does one keep a router on the tiny
surface of the end of the rail?


He has a cool jig to clamp to the rail that holds the router.

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

Tom Watson wrote:
On Mon, 19 Jun 2006 10:57:00 -0500, "Swingman" wrote:

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


I'm not really for either as they stand but might go with a variation
of "B", in what I'd call a double secret probation - uhh, wait a
minute - a "Double Secret Wedged Tenon".

Usually a wedged tenon is a show joint but you can do a secret one by
undercutting the edges of your mortises by the seven degrees described
to form a kind of keystone shaped hollow.

Cut your wedges to fill that seven degree void once they bottom out on
the mortise. Cut the appropriate slots in the tenon. Butter the
tenon and the wedges up and insert the wedges just barely. Drive the
loose tenon home to form a dovetail within the keystoned void. Prep
the other end of the tenon the same way and clamp her up.

You'll wind up with opposing dovetails.


ISTR that those are called fox tenons.

--

FF

"todd" wrote in message

My credentials: degree in mechanical engineering with a specialization in
strength of materials. Formerly a licensed professional engineer in the
state of Illinois. Based on the rough drawing, if you made 10 of these
joints each way and tested them to failure, I'm not sure you could measure
a
statiscally-meaningful difference between the two. Now, I haven't spent
all
night thinking about it, so if someone can make a persuasive argument to
the
contrary, I'm open. So with that said, offhand I'd go with the one you
find
easier to machine.

Very impressive, Todd ... and I appreciate your input. My gut feeling is
that the "easiest to machine", which is also the most precise in this case,
might mitigate any slight strength issues over a run of parts, particularly
if the joints are pinned as planned.

Right now I'm in the process of "jigging up" for a prototype and still have
a good deal of freedom in methodology.

Thanks again for taking the time to respond.

--
www.e-woodshop.net
Last update: 5/6/06

"Tom Watson" wrote in message

It sounds like you are trying to use a router.

I'm not big on round-shouldered joints, regardless of the gluing
surface presented.

I'd use a morticer and be done with it.

I like the lock of the right angled shoulder, and with a joint that is
not haunched, I would particularly look for some right angles in the
joinery.

Just my opinion.

As always YMMV.

I feel the same way, but wanted to explore something different for the
angled and compound angled joints this time around. Most of the other
joints, and there's a ton of them in the back and seat, will be cut with a
morticer.

Been reading too many design tips lately. Seems like the current philosophy
is to design first, then figure out the joinery after the design is cast in
stone.

My first question when I see a piece done that way is "Yabbut, how long will
it last" ... with FLW's falling down "Fallingwater" in mind.

Right now I've got a belt on, but I'm still looking for those suspenders ...
looks like you've found a pair

--
www.e-woodshop.net
Last update: 5/6/06

"Leuf" wrote in message
"Swingman" wrote:

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.


With a router you mean? How does one keep a router on the tiny
surface of the end of the rail?

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.

--
www.e-woodshop.net
Last update: 5/6/06

"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.


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

On 19-Jun-2006, "todd" wrote:

My credentials: degree in mechanical engineering with a specialization in
strength of materials.

Civil eng (Structures) with one old prof that used to toss the textbook and
point out the basics occasionally.

If it was an isotropic material, I might agree, but it's wood and the grain will
dominate the behavior. Wood can exhibit significantly different strengths
depending on orientation relative to grain.

How that joint will behave will depend on factors beyond just the wood or the
orientation of the tenon. If the joint is glued with a seriously stiff and strong
adhesive that prevents any motion in the joint, either will be strong. If the
adhesive can flex, the shape and orientation of the tenon will affect the overall
strength (given the grain). Since I've seen more joints fail due where no
strong adhesive is used or the adhesive lets go, I'd tend to design ignoring the
adhesive and then B is stronger. I wouldn't go with a tenon crossing grain
lines significantly. If the tenon in the drawing is to scale, then the rail is
thin on the periphery - Use B.

If the wood selected has crap grain, either A or B would be equally weak.

Mike

Michael Daly wrote:

Civil eng (Structures) with one old prof that used to toss the
textbook and
point out the basics occasionally.


You had one of those to huh?

Mine wasn't old, just a slave driver.

I still remember his tag line, "Gentlemen, get out your coolie hats,
it's time to go to work."

Lew

"Lee Michaels" wrote in message

Now I gotta go back to being my usual curmudgeon self.

.... 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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Last update: 5/6/06

"Swingman" wrote in message
...
Thanks for the kind words ... I'll be blushing for the next week or two.

--
www.e-woodshop.net
Last update: 5/6/06


As you should ...your one of the guys whom make the wReck a "must read" with
my morning coffee.....Thanks Rod

On Tue, 20 Jun 2006 06:26:30 -0500, "Swingman" wrote:


I feel the same way, but wanted to explore something different for the
angled and compound angled joints this time around. Most of the other
joints, and there's a ton of them in the back and seat, will be cut with a
morticer.

Been reading too many design tips lately. Seems like the current philosophy
is to design first, then figure out the joinery after the design is cast in
stone.

I've always been a fan of form following function. I have enough ego
that I would not like to see a difficult to achieve joint hidden.

I don't know what your constraints are on the design level, so I
responded with what I thought would be a strong joint for the given
conditions.

If I had my way, I'd show the wedged tenon, rather than create a
hidden version. I never really liked the idea of "Secret Mitered
Dovetails" for the same reason.

I didn't like the "A" version because it violated my sense of joinery,
which includes the notion of eliminating as much short grain as
possible.

I'm conversant with the arguments for loose tenons but there is
something about them that sticks in my craw. I'd rather see an honest
tenon on that rail or stretcher, with an exposed wedged tenon. It
seems more craftsmanlike to me.

Some smart fella said something along the lines of, "Joinery is the
beginning of ornament".

All I can say is, "Amen".




My first question when I see a piece done that way is "Yabbut, how long will
it last" ... with FLW's falling down "Fallingwater" in mind.

Right now I've got a belt on, but I'm still looking for those suspenders ...
looks like you've found a pair
Regards,

Tom Watson

tjwatson1ATcomcastDOTnet (real email)

http://home.comcast.net/~tjwatson1/

The saga continues:

http://www.e-woodshop.net/Projects10.htm#Joinery1

Using "B" has always been my preference, particularly once I found a source
for carbide end mills of sufficient length that could be used in a router.

.... nonetheless, the JDS Multi-Router is looking more attractive all the
time.

--
www.e-woodshop.net
Last update: 6/24/06