Double M&T Joints

[ByronBlack]

Does anyone know of a good book, or online article/page that shows how to mark up and cut a double M&T. I've been thinking about it all today and can't visualise how you go about marking and cutting this joint properly. Any help gratefully received, in the meantime, I shall continue to trawl the interweb to see if I can find anything.

 

[woodbloke]

BB to clarify, do you mean a M/T as might be found at the bottom of a door where they (tenons) are 'in line' and separated by a section wot's been removed or a joint where the tenons are parallel to each other, as say in a very large finger joint? - Rob

 

[Steve Maskery]

The answer to how doyou cut them is simple. Very, very carefully.

By far the easiest way is to use loose tenons. You only have to cut accurate mortices that way, and if you have a good router mortice jig they are quick, too. Very strong indeed.

If you cut them by hand, the issues are keeping the shoulders flat all the way round and between the tenons, keeping the tenons the right thickness, keeping them straight and keeping them the right distance apart. Lots to go wrong.

Use a jig and loose tenons. Or the Domino if the job is a suitable size and you are feeling flush.

Cheers
Steve

 

[nickson71]

The answer to how doyou cut them is simple. Very, very carefully.

By far the easiest way is to use loose tenons. You only have to cut accurate mortices that way, and if you have a good router mortice jig they are quick, too. Very strong indeed.

If you cut them by hand, the issues are keeping the shoulders flat all the way round and between the tenons, keeping the tenons the right thickness, keeping them straight and keeping them the right distance apart. Lots to go wrong.

Use a jig and loose tenons. Or the Domino if the job is a suitable size and you are feeling flush.

Cheers
Steve

That the way I'd do them too............ with a router that is

 

[JFC]

OOOOOO is this the first case of us being able to say " removing the relish" :wink:

 

[Paul Chapman]

and if you have a good router mortice jig they are quick, too. Very strong indeed.

And if you don't have a jig, Byron, you could probably make up one quite easily with a couple of pieces of MDF which you could then use with a guide bush. Have a look at this from Ron Fox's tips - not exactly the right thing, but it will give you the rough idea http://www.wealdentool.com/acatalog/tips_5.html

Cheers :wink:

Paul

 

[Scrit]

BB to clarify, do you mean a M/T as might be found at the bottom of a door where they (tenons) are 'in line' and separated by a section wot's been removed

You mean relished? :lol:

OOOOOO is this the first case of us being able to say " removing the relish" :wink:

Yep, I think so :wink:

Scrit

 

[Anonymous]

Byron what are you making with double tenons? For me it means either relieved single tenons as in snap below, or rarely (er, never come to think I can't remember doing one) a side by side tenon to leave room for a mortice lock in between.
Never a loose tenon IMHO except for joining boards in an old fashioned way.
What's this "relish" thing, is it a technical term I've never heard of or summat?
cheers
Jacob

 

[ByronBlack]

Rob - what I mean by double tenon is two tenons parallel to each other from the same wide stock with a gap in the middle.

Here's a pic of what I mean:

It's for my workbench. My bottom stretchers are about 7" wide and i read somewhere that if the stock is over abut 4 or so inches you should use double tenons due to wood movement in the large single tenon.

Steve - would loose tenons be strong enough to join a large stretcher to a trestle leg (for my bench)? Also, I was hoping to have a through wedged tenon for decorate purposes, can you still achieve that with a loose tenon?

Cheers for the ideas/tip so far guys, i'll check out the Fox link, thanks.

 

[JFC]

That's just a haunched mortice and tenon . Cut a full tenon and then rip down to the depth you want and take out the rest with a coping saw until you get a bansaw .
Jacob , Scrit showed a machine that did haunching and relishing but no one knew what relishing was . Scrit found out the other day .
On another note jacob , on your pic you have no haunches just the tenon part , i've never seen that before . Whats the reason behind that please ?

 

[Steve Maskery]

Steve - would loose tenons be strong enough to join a large stretcher to a trestle leg (for my bench)? Also, I was hoping to have a through wedged tenon for decorate purposes, can you still achieve that with a loose tenon?

Size for size, loose tenons are just as strong, and much easier to cut, as traditional tenons. What you have drawn is not what I thought you wanted. That is jstt a nomal tenon with the centre cut out. I though you meant side by side.

Personally for rails in a bench I'd use stub tenons (loose if you like) for location only, and use a bedbolt KD joint for the strength.

If you want through wedges, you'll have to square up the mortices with a chisel, or saw a slit in the tenon (after gluing it into the stretcher) and drive the wedge into the slit. You'll still get a good tight tenon. But if you do that, the bench will be solid and you'll have great difficulty in moving it should you ever need to.

Loose tenons and bedbolts. Fast accurate and strong. What more do you need?

I'm afraid I can't be any more helpful here, but if you email me

 

[Scrit]

Size for size, loose tenons are just as strong, and much easier to cut, as traditional tenons.

Are they just as strong, though? I'd have thought that the continuous grain in a "conventional" tenon would actually have more shear strength - which is probably why joinery manufacturers still use them as opposed to going over to loose tenons - and those guys are really into knock-it out quick. As to being easier to cut, well maybe, but learning how to do a mortise and tenon joint - the basis of a large amount of things we make is surely a skill worth acquiring?

Personally for rails in a bench I'd use stub tenons (loose if you like) for location only, and use a bedbolt KD joint for the strength.

I've tried them but find you keep having to tighten them up. Next heavy bench I make is using foxed M&Ts for the end frames and rails held by wedges - 'coz they're easily adjusted with a "Birmingham screwdriver" :wink:

Scrit

 

[Steve Maskery]

I'd have thought that the continuous grain in a "conventional" tenon would actually have more shear strength

Scrit

I'd have thought that if you use straight-grain timber and a good glue, and given that when a joint fails, it's often the timber rather than the glue, then, to all intents and purposes, there is no appreciable difference.

As to being easier to cut, well maybe, but learning how to do a mortise and tenon joint - the basis of a large amount of things we make is surely a skill worth acquiring?
Scrit

Undoubtedly.

I've tried them [KDs] but find you keep having to tighten them up.

That's one of their advantages. You can tighten them up. And whilst I don't spend as much time at the bench as you do, I can say I've only had to tighten up mine once in ten years or more (just a few months after originally making it, after it had "settled"). I don't consider that to be onerous, and well worth it for the ease of assembly and disassembly.


I simply wouldn't make a bench that way, but if I had to, I'd use a router jig, simply because I have one which is easy to set up, reasonably quick and above all cuts tenons which are accurate, and, if you really want, wedgable too. And I don't need a big router to do it, although of course, it helps. I just don't think it's the best way to go about it for the average home woody like me, that's all

Cheers
Steve

 

[Anonymous]

Byron what are you making with double tenons? For me it means either relieved single tenons as in snap below, or rarely (er, never come to think I can't remember doing one) a side by side tenon to leave room for a mortice lock in between.
Never a loose tenon IMHO except for joining boards in an old fashioned way.
What's this "relish" thing, is it a technical term I've never heard of or summat?
cheers
Jacob

Absolutely!

What he said.

I would not use a loose tenon, especially for a workbench.

As folr the domino, it will not cut deeply enough for your requirement

 

[JFC]

Whats all this about slits in tenons rather than cutting out the mortice to take the wedges !!!!!!! Again another trick for the knock it out fast mass production companies .
Why cant you say more here Steve ? I earn my living from working with wood but always give my tips etc publicly . ( Thats not having a go it was just a question )

 

[Scrit]

I'd have thought that the continuous grain in a "conventional" tenon would actually have more shear strength

I'd have thought that if you use straight-grain timber and a good glue, and given that when a joint fails, it's often the timber rather than the glue, then, to all intents and purposes, there is no appreciable difference.

To my mind there is one annoying but inherrent weakness in any mortise and tenon joint and that is thet you are gluing grain at right angles, i.e. where the shear strength is not the greatest. A conventional M&T has only one "set" of surfaces on which glue line shear failure can occur and that can be overcome in part by fox wedging the joint so that in the event of a failure the joint will still have mechanical strength. Loose tenons on the other hand have two sets of surfaces and I'm not sure that they can be foxed all that effectively without running the risk of splitting them end to end. Or perhaps I'm just being a bit too "traditional" in my approach?

I simply wouldn't make a bench that way, but if I had to, I'd use a router jig, simply because I have one which is easy to set up, reasonably quick and above all cuts tenons which are accurate, and, if you really want, wedgable too. And I don't need a big router to do it, although of course, it helps. I just don't think it's the best way to go about it for the average home woody like me, that's all

Perhaps you're right (about the home woody, that is :wink: ) but I thought Byron was looking to make a traditional joinery base. The "medium weight" benches I've made for myself would probably cause the elitists to throw up their hands in horror - the frames are effectively timber ladder sections with housing joints, glue blocks and screws for goodness sakes. They bolt together with coach bolts...... :roll: Traditional they aren't. Quick, cheap and stable they are and they require no fancy joinery at all. Oh the shame, the shame of it

Byron -

I though you might find these of interest:

Above: Twin Tenons

Below: Double Tenone for Wide Rails

Stages in Cutting Wide Tenons (by hand)

All taken from Charles H. Haywards' "Woodwork Joints" (publ. 1951)

 

[Paul Chapman]

Byron,

Unless you want to cut mortise and tenon joints for the sake of it, you could use a couple of dowels for location and then bolts and nuts to actually hold it together. When I made mine I used 6mm threaded rod, metal cross dowels and brass heads for the threaded rod to hold the base together, as you can see in this picture

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I did it that way because I thought it was going to be a temporary structure, but I've been using it for about 10 years now and it's still completely solid.

All depends really on whether you want it to be an heirloom piece or something that simply works :wink:

Cheers :wink:

Paul

 

[Scrit]

Whats all this about slits in tenons rather than cutting out the mortice to take the wedges !!!!!!! Again another trick for the knock it out fast mass production companies.

Nah - they use dowels, don't they? :roll:

Scrit

 

[Scrit]

Does anyone know of a good book... .....that shows how to mark up and cut a double M&T. I've been thinking about it all today and can't visualise how you go about marking and cutting this joint properly.

Why not try the library for:

"Carpentry & Joinery - Book 1: Job Knowledge" (2nd Edition) by Peter Brett (Nelson Thornes, publ. 2005, ISBN 9 780748 785018).

This is a standard City & Guilds text and is used to teach carpenters and joiners. There is a chapter (Chapter 3) on joints which includes a large variety of techniques together with the proportion "rules" applicable to setting-out various joints and a whole chapter on setting out, mainly site oriented although use of the workshop rod, geometry, etc are dealt with in detail. I'd suggest borrowing this first unless you are really keen to learn about site joinery because I imagine chunks of it will bore you to tears (they do me)

Alternatively go and trawl the Interweb thingy and look for:

"Woodworking Joints" by Charles H. Hayward (publ. Evans)

last published around 1978 (so take a look at Abe Books for a second-hand one, generally better than Amazon I find). Not so good on setting out and nothing about proportions, but nonetheless interesting

Scrit

 

[Anonymous]

That's just a haunched mortice and tenon . Cut a full tenon and then rip down to the depth you want and take out the rest with a coping saw until you get a bansaw .
Jacob , Scrit showed a machine that did haunching and relishing but no one knew what relishing was . Scrit found out the other day .
On another note jacob , on your pic you have no haunches just the tenon part , i've never seen that before . Whats the reason behind that please ?

The haunches are there, 1/2" to fit the slots for the panels. Its the snap, you can't see them very clearly. So "relishing" is taking out the middle bit then? I call it a "relieved" tenon, don't know why, I might have made it up myself: any tenon which is less than the full width of the piece.

how to mark up and cut a double M&T. I've been thinking about it all today and can't visualise how you go about marking and cutting this joint properly.

The answer is as usual: a rod.
One thing is to cut out the centre bit first whilst still all square with all the marks visible, whether or not you've already cut the cheeks, then cut the tenon shoulders last of all - after all moulding, rebating etc

cheers
Jacob