Strength of Domino... Test Results

M

mr_hockey

Member
Joined
Feb 1, 2007
Messages
33
First thing.... I have a Domino & love it!

That being said, I found some disturbing(???) info on another site.

There is a new issue of Wood that compares the strength of different joints.

FYI.... (from another web site...)

"They did use the Iowa State Univerity testing facility, so it wasn't a back yard shoot from the hip kinda thing.
The only one that did really bad was the bisquit in shear and pull a part testing.
# to force break were as follows

Shear
M&T= 1017
Dowelmax=609
Beadlock= 541
Domino= 464
bisquit= 187

pull a part
M&T 2525
Dowel 1866
Domino 1486
Beadlock 1170
bisquit 766

Wood magazine has a online website that may have this on it."

I have not seen the issue of Wood yet, but I would have thought the Domino would be stronger.

Any thoughts????

 
Something doesn't look right to me...  First, DowelMax is a vendor of jigs.  From what I understand, it just makes it easier to align dowel holes.  The Domino is both a tenon and a mortise maker.  Neither the DowelMax nor the Domino tool has any inherent strength; they just make holes. 

So they compared a joint type (M&T) with a jig with a Domino loose tenon with a bisquit.  Something doesn't sound right. 

Also, I have difficulty believing that a dowel (however the holes are drilled) will be stronger than a Domino of the same thickness. 

Would you care to share the site and details?  I want to examine their testing methodology. 

Regards,

Dan.
 
Hmmm, something looks very suspicious now...

I Googled this search string "Festool+domino+test+university+iowa" and got no hits.  This is very odd because most studies of this nature have at least an abstract posted for other scientists. 

Regards,

Dan.
 
I received this magazine yesterday and all the info quoted is what the article states. They do say all except the biscuit are acceptable for most joints though.

I was surprised as well. Won't make me ditch the Domi for a Doweli though.

Gary
 
Performance grades the Domino got all A's or A-'s.

                      Strength of Joint    Ease of Align      Speed of making Joint  Versatility   
Beadlock                A-                            C                              C                        C
Biscuit                  C                              A-                            A                        B
DowelMax              A                              A-                            B                        B+
Domino                A-                            A                              A-                        A

Also all the editors wanted the Domino as one of there tools for making good joints.

Gary
 
Something is wrong with their testing then. There's absolutely no way a dowel is stronger than a Domino. By its very nature, a dowel is a fairly weak joint. The lack of long grain glue surface is what causes this. Dominos have significantly more surface area for gluing, and a large portion of that is long grain.

There's not much that is special about Dominos themselves. They are just loose tenons, nothing more, nothing less. Fine Woodworking did a test on joints and their strength not all that long ago and their findings were substantially different from the ones posted above.

I didn't read the article, so I don't know all the particulars. However, the strength of loose tenons has been analyzed many times in the past. Traditional M&T joints surpass it for strength, but dowels don't even come close, let alone rank higher in strength. Someone screwed something up.
 
It looks like to me that the dowel joints consisted of more than one dowel. Would that make a difference?

Gary
 
Hello,

I own a Dowelmax (as well as a Domino).  I can vouch for the strenght of joints using dowels and the Dowelmax.  I recently decided to break up an extra face frame that I did not need.  The joints were glued with TB III, 2 dowels at each corner, red oak 1 3/4 inches.  The face frame took 7 or 8 strong hits with a hammer before breaking.  Even then the wood broke before the joint did.  I don't really concern myself about what is stronger, dowels or dominoes.  The glue makes them both extremely strong.  I concern myself with precise fits, and speed.  The dowelmax is very precise.  The domino is very fast.  If I didn't have a domino, I could do a lot of nice work with the dowelmax.  I am getting to like the domino more and more as I use it. 
 
I have to agree with Lou here.  The Domino joint is simply a loose tenon, which, IIRC fared very nearly as well as the basic M&T, which was a clear winner.  I, too use dowels, but Domino seems much stronger to me and is faster and more precise - IMO.

I think the testing methodology or something isn't quite and apples - apples thang!
 
Clint, I have to wonder if they had issues with gluing the dominos properly (there were enough threads here about that to suggest that a learning curve when gluing them could very well be an issue) and that led to the poor results (compared to dowels that is). I can't for the life of me think of anything else.

I don't doubt that dowels, when properly done are an acceptably strong joint for many applications. However, I do more than my fair share of demolishing kitchen cabinets, built ins, and so forth. I see a lot of things that are held together with dowels and they break apart fairly easy for me (granted, I tend swing a hammer a lot harder than most people would). 
 
Lou Miller said:
Clint, I have to wonder if they had issues with gluing the dominos properly (there were enough threads here about that to suggest that a learning curve when gluing them could very well be an issue) and that led to the poor results (compared to dowels that is). I can't for the life of me think of anything else.

I don't doubt that dowels, when properly done are an acceptably strong joint for many applications. However, I do more than my fair share of demolishing kitchen cabinets, built ins, and so forth. I see a lot of things that are held together with dowels and they break apart fairly easy for me (granted, I tend swing a hammer a lot harder than most people would). 
Click to expand...

I think you may have at least part of the answer [allowing them some wiggle room].  I haven't checked out their methodology yet, but I am pretty suspect about it. While I haven't done any scientific testing, I did satisfy myself that the floating tenons were really very, very strong.  They seem to be very close, if not equal to my M & T joints, though as I said, there is nothing scientific about my analysis, I, like many others on the list have a couple of years doing what we do.  [I really hate to play that card, but I'm not sure how else to put it]. :-[

I really do think their analysis is flawed somehow...

I think dowells have a place - I often use them to attach face frames to the carcase.  But I don't use them as the only joiner.  I really like using Domino now.  I dropped one of the Domino'd vanities off my work table - no problem at all.  None of the Domino joints budged even a little - not on the carcase, nor the face frame.  The cabinet is as tight as it was before it fell.  Sold me!
 
I also have questions about those results.  Hopefully the article will describe the sizes used for the loose tenon joints.  I'd also like to see how the joints broke.  I can't believe a domino would give before the surrounding wood.  Same with the Beadlock tenons.  I have seen plenty of doweled joints break at the dowel however.  Maybe the domino and Bealock tenons are so strong they doesn't give causing the surrounding wood to break apart where dowels might bend a little before they let go?  Anyway, if memory serves, those results show the domino joints are more than plenty strong for my applications.

I remember another magazine did a test, possibly FWW, where a pinned M&T joint was weaker than a normal M&T joint.  I believe their conclusion that the pin weakened the M&T slightly.

There's a video at the bottom of this page but it doesn't get into the testing.

http://www.woodmagazine.com/wood/story.jhtml?storyid=/templatedata/wood/story/data/1178129509968.xml

PaulD
 
Thanks for the link Paul.

I loved the demo on the acrylic to show the Domo plunge  ;D
 
Um, what glue was used, majority of joint techniques are for alignment more than strength, not all but most...
 
Wow.  It's like someone just said you're daughter is ugly.  I love my Domino.  I love Dowelmax.  There is no way that one dowel is as strong as one domino of any size, however, I've put 10 x 2 inch dowels in a but joint of 5/4 maple.  It's strong as hell.  I could easily put 4 or more domino's in there too.  So, as with all these tests, as they attempt to compare apples to apples, they rarely do.  There should be a relative calculation of total joint surface area and how strength of the joint is measured with reference to that...however, I can't help but think that everyone suddenly has their back up because of all the "AHA!!!"  "I told you!"  Domino detractor threads that this might produce.  EVERYONE that has one, loves it.  It's like one great big surge of "THAT CAN'T BE!  I LOVE MY TOOL THEREFORE IT'S THE BEST!  DAMN ANYONE THAT SAYS DIFFERNT!"  ;D

I do hate tests like that though.  I like reading that my stuff is the best!  When it's not, I could gives a rats behind.  There is WAY more that goes into the incredible usefulness of the Domino rather than a perception that the joint only takes the weight of two adult men jumping up and down on it to break, rather than 2 1/2.

Just my thoughts.
 
I actually thought something along the lines that you're expressing, mot.(well-expressed, he way). We dont want to become so excited about our tools that we lose all objectivity -- that could get us into serious trouble.

On the other hand, there is something flat out counterintuitive about a dowel out-performing a domino in a strength/failure test.  It really doesnt make sense.  I'll wait until I read the article and the editors respond to the inevitable questions about methodology, etc but for now let's just say that the results are suspect -- not based on loyalty to the tool, but common sense.

Dave
 
A dowel is a loose tenon too, isn't it?

It would be difficult to make a valid direct comparison since the cross sectional area and glue surface area of the Domino and dowel it is compared to would have to match. In addition, in the shear test the Domino is directional while the dowel is not. The dowel might be stronger one way but the Domino would be much stronger the other way. They are both plenty strong but the Domino is much easier to use, especially when multiple loose tenons are needed in series. The slightest misaligned with the dowel and you need a heavy mallet to get the parts together. More than slight misaligned and your in deep trouble. The Domino has eliminated that problem. Hurray!
 
Michael Kellough said:
A dowel is a loose tenon too, isn't it?

It would be difficult to make a valid direct comparison since the cross sectional area and glue surface area of the Domino and dowel it is compared to would have to match. In addition, in the shear test the Domino is directional while the dowel is not. The dowel might be stronger one way but the Domino would be much stronger the other way. They are both plenty strong but the Domino is much easier to use, especially when multiple loose tenons are needed in series. The slightest misaligned with the dowel and you need a heavy mallet to get the parts together. More than slight misaligned and your in deep trouble. The Domino has eliminated that problem. Hurray!
Click to expand...

Michael,

Agreed that dowel and domino are both loose tenons.  It just doesnt make sense to me that the Domino would be weaker in terms of shear strength (which is I think the issue) in either direction.  It is possible, I suppose, that if the Domino is made of weaker material than the dowel, and if the diameter of the dowel is larger than the short dimension of the Domino, that the dowel would be stronger.  But then we'd be talking about large dowels made of dense hardwood.  That's why it seems to me that without further investigation, the results are suspect.  It's not that the results are impossible, but the results appear odd and that requires some close examination of methodology I would think.

Dave

 
This doesn't make sense to me either.  The number and size of the Dominos is chosen based on the several factors - a key one is the thickness of the material versus the thickness of the dowel.  So...

Are the rules the same for dowel size and Domino size?  If so, it would seem to me that you would insert the same number of dowels and Dominos for a given thickness board.  For example, if using a 1" thick board, you would choose your dowel size and Domino size for that thickness.  Yes?  And they would be the same thickness.  Yes?

If my example is correct, if a dowel and a Domino have the same thickness, how could the dowel have the same breaking strength and holding power when the domino is 2-3 times wider?

Regards,

Dan.
 
You must log in or register to reply here.

Similar threads

B
Review of Festool Domino DF 500 Q Set (574 283) - Prototype done
Replies
0
Views
5K
BTDT
B
Back
Top