Does a Domino make a Mortise & Tenon joint?

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An interesting question in one of the pro forums:
===="I make some chairs using Festool Dominos. Is it ok to call the joinery "mortise and tenon"? I suppose a more accurate description would be loose tenon, but that sounds bad, like it's not secured.
And, yes, the chairs are sturdy. Sometimes you just need to cut wide slots and make bigger tenons and/or double up.
Thanks!" ==== I'm on the fence on this one.
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Mortise and floating tenon.
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That is what it is.... but can this guy call it a "Mortise & Tenon" joint in his brochure?
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On 2/23/2011 10:46 AM, Robatoy wrote:

IMO, it is technically, a "mortise and tenon joint", and more traditionally, and specifically, a "mortise and feather tenon" joint.
Personally, I would not use the term "mortise and tenon" to advertise this type of joint without specifying the type of mortise and tenon joint.
If I wanted to be modern:
"mortise and floating tenon" as upscale said, or
If I wanted to more strictly traditional/technical:
"mortise and feather tenon"
I think that you would get more traditional structural and engineering agreement on the latter terminology.
That said, the ultimate enforcer would be probably a lawyer.
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My guess would be "yes", but if he didn't qualify it at the same time with specific information about the Domino itself, he'd be doing a disservice to his own brochure. The Domino is such a new advancement to the home woodworker's art of tenon and mortise that without specific details as to how it works, many woodworkers would dismiss it as just another common tool.
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2 mortises and a tenon joint?
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Yes they are mortise and tenon but that is a floating tenon. In many cases that is NOT as strong in the long run as a true pinned tenon joint. The chairs are sturdy today but after 100 years of racking if they don'y have a pin through each side they are not 100% the same as what one would expect from mortise and tenon.
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I would certainly think that after 100 years of racking that a pin through the tennon would be worn out also. I don't buy that a pinned tennon makes a mortise and tennon significantly stronger unless no glue is being used.
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I don't buy that a pinned tennon makes a

We'll have to disagree on that one.
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On Wed, 23 Feb 2011 10:24:56 -0800 (PST), "SonomaProducts.com"

How could a pin make any difference if the joint were immovably glued together?
I'm with Leon on this one. In a glued situation, the pin is merely decoration.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
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1. Glue can fail. 2. Glue adds some level of adhesion to resit pull out. A pin adds considerably more. 3. In a door or drawer or chair especially, therre are racking forces that slowly tear away at the glues adhesion. Once that is disabled the pin remains. 4. Simple physics says the joint is stronger. It has been too long since I did end reaaction and shear force calcs but I'm sombody could quickly prove how strong a 1/4" dowel is in cross section sheer and it is surely more than a waekened face to face glue joint, especially a hundred years from now.
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On Wed, 23 Feb 2011 13:34:32 -0800 (PST), "SonomaProducts.com"

You are apparently using the wrong glue or making loose joints if you have so many failures. Other reasons can be: temperature too low during glueup, adhesive too old, adhesive previously frozen, or skinning time too long.

Good PVA glue joints make two pieces of wood into one. It's the surrounding wood which gives before the glue does.

Chairs are in a world of their own. Imperfect joints allow them to be assembled, and racking forces are more extreme than anywhere else in furniture, so there is a chance of glue failure. But it's the imperfect joint -gap- which causes it.

A glued joint is like grown wood: all one. If anything, the joint would be weaker due to the drilling. Check the joint strength test result for anyone this century and I'll bet you change your tune.
http://woodgears.ca/joint_strength/glue.html http://www.popularwoodworking.com/article/The_Anvil_Test /
and a whole bunch more. http://www.woodstore.net/wojotote.html Only $3.75 for a copy.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
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Never said glue isn't strong. Never said I have experienced a joint failure. I speculated that a pinned joint is stronger than a not pinned joint. None of the tests you point to have anything to do with pinned vs not pinned. So your claims are just retoric just like mine.
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On Thu, 24 Feb 2011 11:29:00 -0800 (PST), "SonomaProducts.com"

I liken glue on wood to welding on metal. They both make two pieces into one. My thoughts are that pins could only decrease the overall strength of the piece. Pinned joints can be very strong, but a glued joint will always be stronger.
I refer you to the parts of those tests which indicate that the wood breaks before the glue joint and ask you how the pin could ever come into action as a strengthener, given a good glueup. I submit that it can -never- do so.
I guess we'll have to agree that we disagree on the point.
-- "Human nature itself is evermore an advocate for liberty. There is also in human nature a resentment of injury, and indignation against wrong. A love of truth and a veneration of virtue. These amiable passions, are the latent spark. If the people are capable of understanding, seeing and feeling the differences between true and false, right and wrong, virtue and vice, to what better principle can the friends of mankind apply than to the sense of this difference?" --John Adams
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All valid points however.... What makes the pin "itself" rot, wear, or break proof. The pin is surely weaker than the wood that makes the tennon, if the tenon wears, the pin has to have worn to allow the tennon to move and wear.
I will give the pin the nod to perhaps helping a failed joint last 1% longer until the pin fails also.
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@swbell.dotnet says...

In the barn I'm working on there are several pinned mortise and tenon joints that are in the process of coming apart--generally the tenon split out behind the pin. This is on 8x8 post and beam construction.
Whether the pin or the tenon is weaker depends on the dimensions of the joint.
It's true that glue can fail. So can a pin. So can a mortise. So can a tenon.
Glue adds a level of resistance to pull out equal to the strength of solid wood. A pin adds less.
Racking forces also tear away at the pin.
Simple physics does not say that the joint is stronger. It is only stronger if the glue has failed.
And why would a glue joint be "weakened" in 100 years if it was properly made? I'm restoring a bookcase right now that's older than that and the hide glue joints on it are still for the most part perfectly sound. The only one that has failed is on a molding and it's clear that somebody pried really hard on it to get it to fail.
Certainly use a pin if it fits the style or if it makes you feel better, but don't delude yourself that it is stronger than an epoxy joint.
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And how many of those joints would have already totally failed if the pin wasn't there as a last resort mechanical assist? I don't think you can say but it seems you are proving my point and at the least have offer no imperical proof I am wrong. And I am certainly not deluded and neither are a few hundred, maybe thousands of years of craftsman who have pinned their joints.
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In article <60c2cc2f-be92-429c-b723-a2f407fdb692

The pin is not a "last resort mechanical assist", it was the only fastener holding the joint together until some cables with turnbuckles were installed.
And the reason it was used is not that it was strong, it was that the joint can be disassembled when the barn needs repair.
If the joints had been tightly fitted and glued they likely would not have come apart at all. But they also would not be amenable to disassembly at need.
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Never said pin won't rot. Said pinned joint is stronger than non pinned joint, especially in the long run. Thanks for agreeing.
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With a "pinned" mortise and tenon joint, it's not going to be the pin, round or square, that fails - it's the wood between it and the end of the tenon that will fail if the joint is subjected to enough Pull The Tenon Out Of The Mortise force.
With modern glues, there have been plenty of tests that show that, with a properly fit mortise and tenon joint, it's the wood fibers on one or both sides of the glued surface that fails, the glued interface is stronger than the adjacent wood fiber connections.
Now about the pin - square peds, oriented so a face on the peg is square to the grain direction, it will distribute Pull Apart forces over more surface area of end grain - than would a round peg - which concentrates forces to a single point.
But backing up, who here is building furniture to hold up to normal day to day forces - for a hundred or more years? And if that is the case, do you think the piece will be valued highly enough to be cared for - for 5 generations? People move two or three or more times in their lifetime. And over five generations there's bound to be changes in the temperature and humidity the piece will live in over the 100 years. And over that 100 years, tastes will change and unless the piece is a Maloof or a Krenov and has not just senitmental value - it's going to leave the family at some point - and become just another piece.
I'm for making things I can use and looks good to my eye. After me - I won't be around to have to fix it if something loosens up.
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