I use a dowelmax doweling jig, and it works great. It can, however, be quite time consuming. Are biscuits close to the same strength? They look like they would be a lot faster, but I thought I'd ask a few questions before paying a few hundred for a new tool. Are there significant differances between buscuit jointers? Are there certain features that I should look for?

In article ,
wesf66 wrote:

I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?

Dowels are about the weakest way of joining wood ever invented. Not
enough effective glue area. Biscuits are better but even Norm Almighty
seems to have gone off them! (Something about getting slight depressions
in the surface after it had been finished)
As far as biscuit jointers go look at the Dewalt or Lamello and then
compare them with the cheap offshore Chaiwanese ones. Buy what you think
is the best for the buck

I have used both. Biscuits are easier to align and
the joint is very strong. Dowels are more difficult to
align precisely, but very strong also.

I supose someone could calculate the surface area
of a cone (dowel) and compare it to the surface area
of a biscuit of various sizes (00, 10, 20) and come
up with a number for joint strength. Maybe
someone has. I think it is kind of silly because we
use this kind of joinery for "casual" projects.

All that said, I tend to use a biscuit vs a dowel
because it is quicker & easier to align.

For the good stuff, I use M&T & take some time.

Lou

In article , wesf66
wrote:


I use a dowelmax doweling jig, and it works great. It can, however,
be
quite time consuming. Are biscuits close to the same strength? They
look
like they would be a lot faster, but I thought I'd ask a few
questions before
paying a few hundred for a new tool. Are there
significant differances
between buscuit jointers? Are there certain
features that I should look
for?


--
wesf66

snip

of a cone (dowel) and compare it to the surface area

snip

err...cylinder....

Lou

wesf66 wrote:
I use a dowelmax doweling jig, and it works great. It can, however,
be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?

Biscuits would be stronger than dowels, although I have no way
of proving that assertion other than my own experience.
They are probably the fastest way of joining other than
bolted metal fixtures or nails.
Dowels let you do tricks like making tops look like they "float"
off a base frame. Can't do that with biscuits.
Watch out if you use thin wood: the biscuit shape can telegraph
back to the surface.

Dunno if there are significant diffs between jointers.
I use the Makita. Suspect the usual quality control issues
of the really cheap tools will apply. Look for something
that lets you change the blade easily. And lets you lock
the fence(s) firmly. Check the fence(s) for wobble when locked.
Check the plunge action for ease and no "sticking".
Check if it is easy to see the index mark in all positions.

In article ,
wesf66 wrote:

I use a dowelmax doweling jig, and it works great. It can, however, bequite
time consuming. Are biscuits close to the same strength? Theylook like they
would be a lot faster, but I thought I'd ask a fewquestions before paying a
few hundred for a new tool. Are theresignificant differances between buscuit
jointers? Are there certainfeatures that I should look for?-- wesf66


I have posted a graphic in ABPW which compares shear/pull strength of
the different methods. Some dowels, tenons, biscuits etc.

Caveat: I did not conduct these tests so I will not vouch for the
accuracy.

But, having said that, I built 8 cherry dining room chairs with doubled
biscuits and after 15 years, not a creak, not a wobble.
Biscuits may not be 'elegant' but they sure are tough if applied right.

I also dare to go out on a limb and state that there is more difference
between brands of biscuits than there is between the better quality
joiners.

YMMV

0¿0

Rob

That looks like the test run by Fine Woodworking. I have one of their
books with that article.

Practical Design Solutions and Strategies
Taunton Press
Article is by John D. Wagner

Choosing the Strongest Joinery for Doors.
Page 52.

One caution. They point out that the failure mode of a biscuit joint is
"catastrophic Failure" - literally an explosive failure of the joint.

The Mortise and tenon is marginally weaker, but tends to fail in such a
manner as to leave the furniture in one piece -- albeit a bit wobbly.

It is a difference of 3 biscuits fail at 2700 lbs. -- 2 biscuits at 2700
lbs. -- and M&T at 2600 lbs of force..

Looks like you have the chart from the magazine article -- a little more
info on it.

Robatoy wrote:
In article ,
wesf66 wrote:


I use a dowelmax doweling jig, and it works great. It can, however, bequite
time consuming. Are biscuits close to the same strength? Theylook like they
would be a lot faster, but I thought I'd ask a fewquestions before paying a
few hundred for a new tool. Are theresignificant differances between buscuit
jointers? Are there certainfeatures that I should look for?-- wesf66



I have posted a graphic in ABPW which compares shear/pull strength of
the different methods. Some dowels, tenons, biscuits etc.

Caveat: I did not conduct these tests so I will not vouch for the
accuracy.

But, having said that, I built 8 cherry dining room chairs with doubled
biscuits and after 15 years, not a creak, not a wobble.
Biscuits may not be 'elegant' but they sure are tough if applied right.

I also dare to go out on a limb and state that there is more difference
between brands of biscuits than there is between the better quality
joiners.

YMMV

0¿0

Rob

--
Will
Occasional Techno-geek

I think over all you would have to first examine the strength of the glues
and then examine the stress of the project. I would use dowels in the
construction of a heavy worktop and biscuits for a more gentle type table. I
don't think the dowel's would break as quickly as the biscuits but that
would also be dependent on dowel diameter vs. biscuit thickness, one could
possibly place 3 dowels in the same cross area as a biscuit.

as for the tools? I use the more then I can afford method.



"wesf66" wrote in message
...

I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?


--
wesf66

In article ,
Will wrote:

One caution. They point out that the failure mode of a biscuit joint is
"catastrophic Failure" - literally an explosive failure of the joint.

The Mortise and tenon is marginally weaker, but tends to fail in such a
manner as to leave the furniture in one piece -- albeit a bit wobbly.

It is a difference of 3 biscuits fail at 2700 lbs. -- 2 biscuits at 2700
lbs. -- and M&T at 2600 lbs of force..

That 100 lbs isn't enough difference to matter. One could probably find
that difference from one end of a board to the other.
But that 'method' of failure is something to consider.
Those 8 chairs I built could fail 'explosively'?
Gooood.
My ex has them. (She's still a ways away from 2700 lbs, but heading that
way..*EG*)

*wringing my hands and snickering in the most evil way*

BWaaaahaaa

0¿0
˜

Rob

Will wrote:
That looks like the test run by Fine Woodworking. I have one of their

books with that article.

The Mortise and tenon is marginally weaker, but tends to fail in such
a
manner as to leave the furniture in one piece -- albeit a bit wobbly.

Will, I believe that you quoted the article accurately. However, I
have another article published by FWW that says just the opposite. The
M&T was the king of strength, showing three times the more than twice
the strength of double biscuits. This was tested in a laboratory.

Personally, I think double biscuits are pretty strong for many types of
joinery and "good enough" so the discussion is academic anyway.

Bob

wrote in message

Will, I believe that you quoted the article accurately. However, I
have another article published by FWW that says just the opposite. The
M&T was the king of strength, showing three times the more than twice
the strength of double biscuits.

Without any facts to back it up, I'd tend to agree with you. In most
instances, a mortise and tenon has a much larger gluing surface than most
other forms of gluing. Of course, much of this testing applied under
laboratory conditions depends on how pressure is applied to the joint as
compared to how stresses are applied under 'everyday' usage.

wesf66 wrote:

I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?


No one else seems to have mentioned...

If you're edge joining and using the dowel/biscuit for alignment, the
strength of the joint isn't in either.

If you're talking about using them in places where otherwise would be
something like a M&T, it's an indeterminate question as posed since any
comparison will depend quite largely on the size/number of the
dowel(s)/biscuits and the loading orientation.

I'll agree as one of the items often not quoted with the test results is the
type of stress that's applied. With dowels, the weakest direction is when
they're pulled directly out of the joint, as opposed to breaking. OTOH, moving
from smooth dowels to ridged dowels to ringed dowels makes a big difference,
yet most tests only say "dowels" and no more.
GerryG

On Thu, 03 Mar 2005 05:02:27 GMT, "HMFIC-1369" wrote:

I think over all you would have to first examine the strength of the glues
and then examine the stress of the project. I would use dowels in the
construction of a heavy worktop and biscuits for a more gentle type table. I
don't think the dowel's would break as quickly as the biscuits but that
would also be dependent on dowel diameter vs. biscuit thickness, one could
possibly place 3 dowels in the same cross area as a biscuit.

as for the tools? I use the more then I can afford method.



"wesf66" wrote in message
...

I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?


--
wesf66

Peter Hyde wrote:
In article ,
wesf66 wrote:

I use a dowelmax doweling jig, and it works great. It can,
however, be
quite time consuming. Are biscuits close to the same strength?
They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there
certain
features that I should look for?

Dowels are about the weakest way of joining wood ever invented. Not
enough effective glue area. Biscuits are better but even Norm
Almighty
seems to have gone off them! (Something about getting slight
depressions
in the surface after it had been finished)

Are you being sarcastic? You glue up with a biscuit, the glue swells
the biscuit, you sand, the glue on the biscuit dries, the biscuit
shrinks, a depression is formed where you sanded.

wrote:
Will wrote:

That looks like the test run by Fine Woodworking. I have one of their


books with that article.


The Mortise and tenon is marginally weaker, but tends to fail in such

a

manner as to leave the furniture in one piece -- albeit a bit wobbly.


Will, I believe that you quoted the article accurately. However, I
have another article published by FWW that says just the opposite. The
M&T was the king of strength, showing three times the more than twice
the strength of double biscuits. This was tested in a laboratory.

That is why I was specific about the article quoted. It goes on to say
that they believed the M&T may have not been made as good as it should
have been.

The failure mode as I noted is probably a more significant issue. Unless
you put more that 2700 lbs per joint on the chair...

I suspected that they might re-run the tests one day. It just did not
seem right that biscuits should win. Not in a "Fine Woodworking" mag. LOL



Personally, I think double biscuits are pretty strong for many types of
joinery and "good enough" so the discussion is academic anyway.

Bob

Agreed!



--
Will
Occasional Techno-geek

Robatoy wrote:
In article ,
Will wrote:


One caution. They point out that the failure mode of a biscuit joint is
"catastrophic Failure" - literally an explosive failure of the joint.

The Mortise and tenon is marginally weaker, but tends to fail in such a
manner as to leave the furniture in one piece -- albeit a bit wobbly.

It is a difference of 3 biscuits fail at 2700 lbs. -- 2 biscuits at 2700
lbs. -- and M&T at 2600 lbs of force..


That 100 lbs isn't enough difference to matter. One could probably find
that difference from one end of a board to the other.
But that 'method' of failure is something to consider.
Those 8 chairs I built could fail 'explosively'?
Gooood.
My ex has them. (She's still a ways away from 2700 lbs, but heading that
way..*EG*)

She just needs to flop down (i.e. "beach") in one of them and you may
have your wish. People tend to ignore "impact" forces in their designs.
Hopefully it was some of your early work and you did not consider such
stresses...

*wringing my hands and snickering in the most evil way*

Yes you are a "truly evil" person. Happy now. LOL


Wishing you "evil happenings" -- but in the nicest way. ;-)


BWaaaahaaa

0¿0
˜

Rob

--
Will
Occasional Techno-geek

Larry Bud wrote:
....
Are you being sarcastic? You glue up with a biscuit, the glue swells
the biscuit, you sand, the glue on the biscuit dries, the biscuit
shrinks, a depression is formed where you sanded.

I know folks keep saying that, but I've never been able to observe it...

Maybe because I work slowly enough owing to other constraints that by
the time I get from initial construction to finishing things have dried
already or (more likely) the thickness of the piece is sufficient as to
make the differential exapnsion unobservable w/o more precise
measurement than I'm ever going to make on a wooden surface....

On Wed, 2 Mar 2005 20:21:46 +0000, wesf66
wrote:


I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?

I think you have opened a can of worms...lol

I do own a PC biscuit jointer ..and I do use it....

BUT to be very honest I tend to use dowels much more....as they
(Dowel) just seem to "fit" the work I do ...

Not going to comment on the strenght issue... both work well enough
for what I do...

Brands....? I settled on the PC.. BIt only after extensive thought
(2-3 minutes)....

Bob Griffiths

The Mortise and tenon is marginally weaker, but tends to fail in such a
manner as to leave the furniture in one piece -- albeit a bit wobbly.

It is a difference of 3 biscuits fail at 2700 lbs. -- 2 biscuits at 2700
lbs. -- and M&T at 2600 lbs of force..


With no scientific or laboratory test results to back this up I will say the
mortise & tenon is stronger than dowels or biscuits. We did a home shop
test with the following results.

We used alder as the test wood. Making a face frame 12"x15" out of 3/4" x
3".
We made one frame using biscuits 2 per joint, one with dowels 3 - 3/8" x 3",
one with pocket screws (2) and one with MT, two corners were cut and two
were loose tenons.
All were glued with the same yellow glue and allowed to dry for 2 weeks.

Then using the shop press we put each into the press in a diamond shape and
pressed away.

The pocket screws failed first followed closely by the dowels and then the
biscuits. The MT joints were significantly tougher. However, since we were
surprised at how quickly the previous 3 joints failed we tried something
new.

Making more frames - same as above, we tried different clamping methods.
Other than the pocket screws, we clamped in the typical method holding first
then we added clamps to the actual joint - think compressing the mortise
onto the tenon. Wow, what a difference in strength!

Using the same (un-scientific) method of destruction, we found that again,
the screws failed first, then the dowels but with greater force than before.
The real difference was with the biscuits and MT. After pressing much
harder, the biscuit joint failed. The MT (not much difference between the
loose and fixed tenon) really took quite a bit more pressure before they
failed.

Summary, from weak to strong, pocket screws, dowels, biscuits, and way
stronger, mortise and tenon. And for real strength, clamp in both
directions!

Dave



Posted Via Usenet.com Premium Usenet Newsgroup Services
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In article ,
Duane Bozarth wrote:

Larry Bud wrote:
...
Are you being sarcastic? You glue up with a biscuit, the glue swells
the biscuit, you sand, the glue on the biscuit dries, the biscuit
shrinks, a depression is formed where you sanded.

I know folks keep saying that, but I've never been able to observe it...

Maybe because I work slowly enough owing to other constraints that by
the time I get from initial construction to finishing things have dried
already or (more likely) the thickness of the piece is sufficient as to
make the differential exapnsion unobservable w/o more precise
measurement than I'm ever going to make on a wooden surface....

I have never noticed it either and I have used one sh*itload of biscuits
in my day. Mostly edge-to-edge joining of panels, counter tops etc.
Never seen it. But, like in your case, plenty of time passes from
initial assembly to finish.
I also don't have a polarizegraphospectroscopometer like Norm either.

0?0
?

Rob

On Wed, 2 Mar 2005 20:21:46 +0000, wesf66
wrote:


I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?

I've ALWAYS used dowels and a doweling jig.. (30+ years)
and, I've always hated them but saw them as a necessary evil of some types of
joints..

Since getting the dewalt/craftsman b-joiner last year, I've put away my dowel
stuff in a deep, dark corner somewhere... IMO, biscuits make the dowel old
fashioned (not always a bad thing) and hard to align..

I seemed that no matter how precise I thought I was, (dowel jig, drill press,
etc.), some joints were just a bit off.. no problem with a biscuit, but hell
with a dowel..


mac

Please remove splinters before emailing

"Bob G." wrote in message
...
On Wed, 2 Mar 2005 20:21:46 +0000, wesf66
wrote:


I use a dowelmax doweling jig, and it works great. It can, however, be
quite time consuming. Are biscuits close to the same strength? They
look like they would be a lot faster, but I thought I'd ask a few
questions before paying a few hundred for a new tool. Are there
significant differances between buscuit jointers? Are there certain
features that I should look for?

I think you have opened a can of worms...lol

I do own a PC biscuit jointer ..and I do use it....

BUT to be very honest I tend to use dowels much more....as they
(Dowel) just seem to "fit" the work I do ...

Not going to comment on the strenght issue... both work well enough
for what I do...


Start with a concept of load.

A biscuit installed parallel to the load has the shear strength of the glue
that holds it. A dowel - loose tenon - has far greater shear strength. A
biscuit installed perpendicular to the load has much greater strength, but
is still only 1/8" thick, vs. 3/8 or 1/2.

Then think withdrawal. Here the initial nod also goes to the dowel for as
long as the glue remains sound. Unfortunately, it's a cross-grain
situation, and the dowel will work loose of the glue with humidity cycles.
The biscuit suffers much less, and so over the long run will be better.

Now return to a real M/T and notice that it's also a great shear joint, but
cross-grained, and subject to the same, if lesser problems than its round
cousin. We pin the tenon, and there's a new shear kid in town. We have to
shear the pin to withdraw the joint. This is made extremely difficult by
the registry of the shoulder of the tenon with the face of the mortise.

"Duane Bozarth" wrote in message
...

I know folks keep saying that, but I've never been able to observe it...

Chris DeHut - the guy who produces Woodworking at Home DVD did a nice
'speriment on this. His approach and explanation made sense to me. He used a
dial indicator to show that a depression can appear.




Now I know what you're thinking - it doesn't take a dial indicator to know
when you're depressed...

patrick conroy wrote:

"Duane Bozarth" wrote in message
...

I know folks keep saying that, but I've never been able to observe it...

Chris DeHut - the guy who produces Woodworking at Home DVD did a nice
'speriment on this. His approach and explanation made sense to me. He used a
dial indicator to show that a depression can appear.

Now I know what you're thinking - it doesn't take a dial indicator to know
when you're depressed...



OK, what was the average depression he measured?

"George" george@least wrote in message
...
Start with a concept of load.

A biscuit installed parallel to the load has the shear strength of the
glue
that holds it. A dowel - loose tenon - has far greater shear strength.

Do you have some data for this? I'm sure you could calc the shear strength
of a hardwood dowel.
But where is your data showing that the glue has less shear strength? And is
it really the shear of the glue or the shear of the biscuit itself which is
at issue? I think I saw some photos of destructive testing of biscuit joints
out there. I seem to recall that they did not fail at the biscuit. Loose
tenons are a different story.

A biscuit installed perpendicular to the load has much greater strength,
but
is still only 1/8" thick, vs. 3/8 or 1/2.

And is much wider. The cross section of the typical biscuit is much larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the loose
tenon was invented.

Then think withdrawal. Here the initial nod also goes to the dowel for as
long as the glue remains sound.

I suggest you calculate the surface area before you make this conclusion.
I'm not going to do the math for you though. It looks like it is close.

Now return to a real M/T and notice that it's also a great shear joint,
but
cross-grained, and subject to the same, if lesser problems than its round
cousin. We pin the tenon, and there's a new shear kid in town. We have
to
shear the pin to withdraw the joint. This is made extremely difficult by
the registry of the shoulder of the tenon with the face of the mortise.

In article ,
Duane Bozarth wrote:
patrick conroy wrote:

"Duane Bozarth" wrote in message
...

I know folks keep saying that, but I've never been able to observe it...

Chris DeHut - the guy who produces Woodworking at Home DVD did a nice
'speriment on this. His approach and explanation made sense to me. He used a
dial indicator to show that a depression can appear.

Now I know what you're thinking - it doesn't take a dial indicator to know
when you're depressed...



OK, what was the average depression he measured?

Would that be Hamilton or Goldberg?


--

Larry Wasserman Baltimore, Maryland

"J" wrote in message
...
"George" george@least wrote in message
...
Start with a concept of load.

A biscuit installed parallel to the load has the shear strength of the
glue
that holds it. A dowel - loose tenon - has far greater shear strength.

Do you have some data for this? I'm sure you could calc the shear strength
of a hardwood dowel.
But where is your data showing that the glue has less shear strength? And
is
it really the shear of the glue or the shear of the biscuit itself which
is
at issue? I think I saw some photos of destructive testing of biscuit
joints
out there. I seem to recall that they did not fail at the biscuit. Loose
tenons are a different story.

A biscuit installed perpendicular to the load has much greater strength,
but
is still only 1/8" thick, vs. 3/8 or 1/2.

And is much wider. The cross section of the typical biscuit is much larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the
loose
tenon was invented.

Then think withdrawal. Here the initial nod also goes to the dowel for
as
long as the glue remains sound.

I suggest you calculate the surface area before you make this conclusion.
I'm not going to do the math for you though. It looks like it is close.

Now return to a real M/T and notice that it's also a great shear joint,
but
cross-grained, and subject to the same, if lesser problems than its
round
cousin. We pin the tenon, and there's a new shear kid in town. We have
to
shear the pin to withdraw the joint. This is made extremely difficult
by
the registry of the shoulder of the tenon with the face of the mortise.

"George" george@least wrote in message
...

"J" wrote in message
...
"George" george@least wrote in message
...
Start with a concept of load.

A biscuit installed parallel to the load has the shear strength of the
glue
that holds it. A dowel - loose tenon - has far greater shear
strength.

Do you have some data for this? I'm sure you could calc the shear
strength
of a hardwood dowel.
But where is your data showing that the glue has less shear strength?
And
is
it really the shear of the glue or the shear of the biscuit itself which
is
at issue? I think I saw some photos of destructive testing of biscuit
joints
out there. I seem to recall that they did not fail at the biscuit. Loose
tenons are a different story.

A biscuit installed perpendicular to the load has much greater
strength,
but
is still only 1/8" thick, vs. 3/8 or 1/2.

And is much wider. The cross section of the typical biscuit is much
larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the
loose
tenon was invented.

Then think withdrawal. Here the initial nod also goes to the dowel
for
as
long as the glue remains sound.

I suggest you calculate the surface area before you make this
conclusion.
I'm not going to do the math for you though. It looks like it is close.

Now return to a real M/T and notice that it's also a great shear
joint,
but
cross-grained, and subject to the same, if lesser problems than its
round
cousin. We pin the tenon, and there's a new shear kid in town. We
have
to
shear the pin to withdraw the joint. This is made extremely difficult
by
the registry of the shoulder of the tenon with the face of the
mortise.

Good to see we are in complete agreement!

-j

"J" wrote in message
...

And is much wider. The cross section of the typical biscuit is much larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the
loose
tenon was invented.


What about the cross section of two dowels in the same space a biscuit would
occupy?
--

-Mike-

--
'
"Mike Marlow" wrote in message
...

"J" wrote in message
...

And is much wider. The cross section of the typical biscuit is much
larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the
loose
tenon was invented.


What about the cross section of two dowels in the same space a biscuit
would
occupy?

Do the math.
Cross section of dowel = PI x r^2
Cross section of biscuit = length x thickness (#20 is 2.375 x 0.147)
So it would take three 3/8" diameter dowels to match the shear strength of
a #20 biscuit or two 1/2" dowels.
Assuming the same strength of materials.

-j

On Thu, 3 Mar 2005 15:52:16 -0500, "Mike Marlow"
wrote:


"J" wrote in message
...

And is much wider. The cross section of the typical biscuit is much larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the
loose
tenon was invented.


What about the cross section of two dowels in the same space a biscuit would
occupy?


shear is a direct function of section. a dowel with a given section is
much thicker than a biscuit of the same section, so it weakens the
board it's in more. dowel joints often fail by blowing out the wood
surrounding the dowel rather than breaking the dowel itself.

On Thu, 3 Mar 2005 14:33:26 -0800, "J" wrote:


What about the cross section of two dowels in the same space a biscuit
would
occupy?

Do the math.
Cross section of dowel = PI x r^2
Cross section of biscuit = length x thickness (#20 is 2.375 x 0.147)
So it would take three 3/8" diameter dowels to match the shear strength of
a #20 biscuit or two 1/2" dowels.
Assuming the same strength of materials.

Do more math: The dowel has the same cross-section throughout the
penetration into both pieces of wood, and the biscuit cross-section
lessens away from the joint. And, with today's glues the joint will
be the last to go. That makes the dowels the winners. Also there is
no comparison with strength of materials; a solid hardwood dowel wins
hands down over pressed paper.

We can theorise all we want until there is solid scientific
[experimental results] evidence one way or another to back up "common
sense". The point is that if you drop a ton weight on it, it won't
matter either way, and barring that, either is "strong enough", and
the important factor is ease and accuracy of assembly and cost, not
strength.

On Thu, 03 Mar 2005 20:01:05 -0500, Guess who
wrote:

On Thu, 3 Mar 2005 14:33:26 -0800, "J" wrote:


What about the cross section of two dowels in the same space a biscuit
would
occupy?

Do the math.
Cross section of dowel = PI x r^2
Cross section of biscuit = length x thickness (#20 is 2.375 x 0.147)
So it would take three 3/8" diameter dowels to match the shear strength of
a #20 biscuit or two 1/2" dowels.
Assuming the same strength of materials.

Do more math: The dowel has the same cross-section throughout the
penetration into both pieces of wood, and the biscuit cross-section
lessens away from the joint. And, with today's glues the joint will
be the last to go. That makes the dowels the winners. Also there is
no comparison with strength of materials; a solid hardwood dowel wins
hands down over pressed paper.

1) shear happens at the joint. that is the measure that matters for
shear. other modes of failure vary, but the section at the joint is
the relevant one for most of them.

2)biscuits are made from beech, not paper. most dowels are made from
birch. anybody with hard data about those species? I'm betting beech
has better strength than birch....



We can theorise all we want until there is solid scientific
[experimental results] evidence one way or another to back up "common
sense". The point is that if you drop a ton weight on it, it won't
matter either way, and barring that, either is "strong enough", and
the important factor is ease and accuracy of assembly and cost, not
strength.


ease of use favors biscuits, unless you're talking about using big
dollar multi-spindle dowelling machines. strength data goes either
way, depending who you're talking to...

On Thu, 03 Mar 2005 17:57:23 -0700, s wrote:

On Thu, 3 Mar 2005 15:52:16 -0500, "Mike Marlow"
wrote:


"J" wrote in message
...

And is much wider. The cross section of the typical biscuit is much larger
than the cross section of the dowel.
A #20 biscuit has a cross sectional area of 0.35 sq in. You would need a
dowel 2/3 inches in diameter to match that cross section.
Not easy to use that size of dowel in 4/4 stock. :-) This is why the
loose
tenon was invented.


What about the cross section of two dowels in the same space a biscuit would
occupy?


shear is a direct function of section. a dowel with a given section is
much thicker than a biscuit of the same section, so it weakens the
board it's in more. dowel joints often fail by blowing out the wood
surrounding the dowel rather than breaking the dowel itself.

Ahh, I've been waiting to see if anybody raised that rather practical point!
I've also seen whole dowels pulled out of a joint, but I've never seen a
biscuit do so, as it breaks instead. Part of this may be the dowel having a
weaker glue joint, due to the relatively large amount of end grain. Once it
starts to fail, it either pulls out of the joint, or acts as a lever to blow
out the side of the wood.

Now, has anybody compared the difference between dowels, from smooth to ridged
to ringed? I've heard said that a ringed dowel is far stronger, but haven't
tried it or seen any data. Similarly, we now have the Miller dowel system as
another variable.
GerryG

"J" wrote in message
...


--
'

What about the cross section of two dowels in the same space a biscuit
would
occupy?

Do the math.
Cross section of dowel = PI x r^2
Cross section of biscuit = length x thickness (#20 is 2.375 x 0.147)
So it would take three 3/8" diameter dowels to match the shear strength
of
a #20 biscuit or two 1/2" dowels.
Assuming the same strength of materials.


Sorry J - I wasn't asking what the cross section was. Typed out my reply in
too much of a hurry. I was headed down the strength of materials road. Was
it George or you that just posted the home brewed trials the other day?
That proved to be a very interesting observation.
--

-Mike-

--
'
"Guess who" wrote in message
...
On Thu, 3 Mar 2005 14:33:26 -0800, "J" wrote:


What about the cross section of two dowels in the same space a biscuit
would
occupy?

Do the math.
Cross section of dowel = PI x r^2
Cross section of biscuit = length x thickness (#20 is 2.375 x 0.147)
So it would take three 3/8" diameter dowels to match the shear strength
of
a #20 biscuit or two 1/2" dowels.
Assuming the same strength of materials.

Do more math: The dowel has the same cross-section throughout the
penetration into both pieces of wood, and the biscuit cross-section
lessens away from the joint.

Think about this a minute. You know how a pair of scissors (shears) cut
paper? One side goes one way the other goes the other way... that is what
shear is. Now you are telling us that because the dowel is longer it is more
resistant to shear? If that were true cutting a 1" wide strip of paper
across the width would be more difficult as the length of the paper gets
longer. I'm sure that you can prove to yourself that this is false.

There is no shear force at the base of the biscuit or the root of the dowel
unless the wood it is embedded in is split.


And, with today's glues the joint will
be the last to go. That makes the dowels the winners.

Actually no.

Also there is
no comparison with strength of materials; a solid hardwood dowel wins
hands down over pressed paper.

Biscuits (at least all that I've ever seen) are compressed hardwood. I
wouldn't use a paper biscuit.

We can theorise all we want until there is solid scientific
[experimental results] evidence one way or another to back up "common
sense".

Actually theory is quite useful in predicting the results. This is how the
entire profession of engineering works.
Calculation of shear is something that is well defined and done everyday.
There is no doubt that a #20 biscuit has more resistance to shear than a
3/8" dowel.

The point is that if you drop a ton weight on it, it won't
matter either way, and barring that, either is "strong enough", and
the important factor is ease and accuracy of assembly and cost, not
strength.

That may be your point. My point was that it is not a good idea to give
false information. What you have stated is false. Biscuits are not made of
paper. Resistance to shear is proportional to cross sectional area and a #20
biscuit has about the same cross sectional area as a 2/3" dowel.

-j

"Mike Marlow" wrote in message
...
Sorry J - I wasn't asking what the cross section was. Typed out my reply
in
too much of a hurry. I was headed down the strength of materials road.
Was
it George or you that just posted the home brewed trials the other day?
That proved to be a very interesting observation.
--

My remarks were general observations on the nature of the three joints. The
ad hominem remarks made it clear that J is a convinced individual -
convinced that he's correct. I elected not to play.

Now, once again, you have the two loads to consider, and the information I
gave is accurate. Further, you have to consider the instantaneous blow -
the one which eliminates biscuits oriented along the line of load as
worthwhile alternatives.

"George" george@least wrote in message
...

"Mike Marlow" wrote in message
...
Sorry J - I wasn't asking what the cross section was. Typed out my
reply
in
too much of a hurry. I was headed down the strength of materials road.
Was
it George or you that just posted the home brewed trials the other day?
That proved to be a very interesting observation.
--

My remarks were general observations on the nature of the three joints.
The
ad hominem remarks made it clear that J is a convinced individual -
convinced that he's correct. I elected not to play.


Which ad hominem remarks? I don't think I posted anything like that.

-j