Dowels vs. Biscuits. Speed vs. Strength

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

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.... :)
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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
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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...
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patrick conroy wrote:

:)
OK, what was the average depression he measured?
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Would that be Hamilton or Goldberg?
--

Larry Wasserman Baltimore, Maryland
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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

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-- wesf66
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<snip>

<snip>
err...cylinder....
Lou
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wesf66 wrote:

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.
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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
00
Rob
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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:

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Will
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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
00
Rob
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Robatoy wrote:

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...

Yes you are a "truly evil" person. Happy now. LOL
Wishing you "evil happenings" -- but in the nicest way. ;-)

--
Will
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Will wrote:

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
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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.
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snipped-for-privacy@yahoo.com wrote:

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

Agreed!
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Will
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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
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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.

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