Thread: M&T v's Loose Tenon Joints

Here’s my untested thinking on the matter: we always say that modern glues are stronger than wood, so the loose tenon in long grain should be every bit as strong. The cross grain piece is the same no matter which method you use. I do mostly big scale stuff so find the 14mm domino adequate for up to 40mm timber without resorting to a double row of tenons.

I always use the tight setting by the way, on both pieces. Wide slots are fine if you are using dominos like biscuits, but they negate the advantage of a snug fit if doing structural M & T joints. I also have started making my own dominos so custom widths are a possibility too, although obviously some jigging would be required to get a custom mortise cut accurately.

I built 27 six-panel doors for my Georgian house and used 34 dominos in each one. That was a total of 1836 cuts and 128 metres of dominos. No creaks, still square but I am only two years into a hundred year test cycle.

A tenon being part of the rail doesn't have any end grain to end grain glue or gaps like a loose tenon does at both ends. Its stronger because of that .

Other good reasons for Mortise and tenon.
The tenon in the mortise is better on assembly before the glue dries for keeping things close in the same plane and not twisting around so bad.

And tenons are quicker. I'm doing a cabinet atm that has 60 M&T in its base and 4 doors.
So 60 Mortise and 60 Tenon compared to loose tenoning with 120 Mortise and 60 loose tenons being made . Quite a saving of time.

Also for frame and panel construction, because of the way that Mortise and tenon lines up with the panel slot in the rail and stile it is a good common sense way of building . The slot is filled on the end grain with the haunch , part of the tenon left on to fill that gap. The slot is the same width as the M&T. There is no ridiculous doing panel slots in a different location to the M&T if your doing it right. An easy and smart way of doing it.

If you're taking into account only strength and durability then the difference is negligible, assuming the joint is assembled well.

However like what Auscab points out there's much more to a joint than just strength and durability. Speed of construction, cost of construction, ease of assembly, ease of construction are a few factors that come into play when determining which joint to use.

Not sure that I understand about locating the tenon. I use a domino xl and can choose where the tenon will be located, and the depth of the slot. Frame and panel constructions are typically made with cope and stick cutters, so the rails nest in the stiles. The loose tenon goes right in the middle of the joint and does not interfere with any of the other elements of the construction.

I have hand chopped mortices before, not doing that again. I like oscillating chisel mortisers, but they are rare as hen's teeth and expensive.

Thanks for the replies, Greg I hadn't even given the Domino any thought, my thinking was a loose tenon about the same size as a fixed tenon, the Domino I regard as more for alignment purposes and I never glue them though I realise that is not how most people use the machine. The question arises because I can cut mortises on my new router table as an automatic process and I can size loose tenons on my A3-31 thicknesser to exactly match the mortise size.

Because of the automation built into the RT I am looking at different ways it can be used when we finally finish it which I can thankfully say is very close because it has been a journey of several years. While I write this it occurred to me that I can do fixed tenons on it as well with no measuring just using the dimensions from the mortise so my question about the loose tenons is most probably redundant.

With sizings, etc. being more or less equal, my take on it is that M&T's have one less glue joint, hence one less possible point of failure.

The only time I'll use loose tenons is where side-grain meets side-grain and a tenon is impractical. Even then I'm often more likely to use a spline or biscuits instead and rely on glue strength. But not always... sometimes there is a need, although off the top of my head I can't name an example.

Originally Posted by Skew ChiDAMN!!

The only time I'll use loose tenons is where side-grain meets side-grain and a tenon is impractical.

I can't imagine a single example of this possibility in anything I've ever made. Just can't get my head around it. I'm a big fan of loose tenons. You can make the tenon stock in such long lengths that I can't see a time disadvantage, and there is the possibility of saving material due to not needing extra length for a tenon.

Don't most of us join side grain to side grain without anything other than glue all the time? For instance if making any kind of a table/bench top.

Chris, you didn't mention what the application that you were referring to.

For joinery a mortice and tenon joint is far superior. I was involved in a court case involving twenty six full size doors that had failed. Those doors were assembled using domino construction and built in a professional joinery shop. Admittedly there are many possibilities that may have contributed to the failure. The outcome for cabinet joinery using a loose method may have been quite different, but would still prefer a mortice and tenon joint.

I haven't, in probably sixty years, witnessed a failure like the first instance.

In open veranda construction, loose tenons were often successfully used at one end of baluster and hand rails between veranda posts and newel posts. As has already mentioned, accurate construction, application and time factors, play a part in making a decision.

Jim

My question was general in nature with no specific application in mind.

Originally Posted by powderpost

Chris, you didn't mention what the application that you were referring to.

For joinery a mortice and tenon joint is far superior. I was involved in a court case involving twenty six full size doors that had failed. Those doors were assembled using domino construction and built in a professional joinery shop. Admittedly there are many possibilities that may have contributed to the failure. The outcome for cabinet joinery using a loose method may have been quite different, but would still prefer a mortice and tenon joint.

What was the outcome?


I use a lot of dominos at my school. We make footstools, , desks, chairs, side tables and even a couple of dining tables (and more). Haven't had an issue yet. None of our products are under a large amount of stress though.
I always wonder if I'm doing the students a disservice by using the domino joiner so much but it makes everything so easy and quick. You don't need much skill to draw a line and push.

Originally Posted by aldav

I can't imagine a single example of this possibility in anything I've ever made. Just can't get my head around it. I'm a big fan of loose tenons. You can make the tenon stock in such long lengths that I can't see a time disadvantage, and there is the possibility of saving material due to not needing extra length for a tenon.

Don't most of us join side grain to side grain without anything other than glue all the time? For instance if making any kind of a table/bench top.

Yep. But I'm betting that you're thinking in terms of good design practises. When building other people's designs, well... :shudder:

A couple of pros for loose tenons: Increase strength with stronger timber specie. Save tenon lengths on expensiive, decorative stock. I make and repair a lot of chairs. The main repair is usually joint failure. Particularly dowel or biscuit. Therefore I am not a lover of either. The greater the surface area the better the joint.

Originally Posted by powderpost

Chris, you didn't mention what the application that you were referring to.

For joinery a mortice and tenon joint is far superior. I was involved in a court case involving twenty six full size doors that had failed. Those doors were assembled using domino construction and built in a professional joinery shop. Admittedly there are many possibilities that may have contributed to the failure. The outcome for cabinet joinery using a loose method may have been quite different, but would still prefer a mortice and tenon joint.

I haven't, in probably sixty years, witnessed a failure like the first instance.

In open veranda construction, loose tenons were often successfully used at one end of baluster and hand rails between veranda posts and newel posts. As has already mentioned, accurate construction, application and time factors, play a part in making a decision.

Jim

Just out of curiosity what size dominos and how many? Was it a glue failure? What glue?

I had a eye-poppingly expensive quote for my doors and they were planning to use dowels.

Originally Posted by rustynail

A couple of pros for loose tenons: Increase strength with stronger timber specie. Save tenon lengths on expensiive, decorative stock. I make and repair a lot of chairs. The greater the surface area the better the joint.

I agree with these points. I have a slot morticer and have been using loose tenons for over 30 years. I make them from Vic Ash, which is usually considerably stronger than the timber being joined. Consider how strong the tenon on an Australian cedar chair rail would be. I can scale the loose tenons up or down to suit the job. A table gets 12mm tenons about 100mm long. A chair gets 10mm loose tenons. With adequate surface area there’s no way the glue is letting go.

And finally, I find machining slots is foolproof, whereas cutting the cheeks of a tenon is challenging.