Mortise & Tenons

[jfynyson]

I'm gearing up to make a few small projects where I would like to incorporate mortise & tenons for both functionality and visual appeal but mainly to get practice at it. I searched this forum and saw bits & pieces of my questions answered so thought I'd start this thread if that's ok to capture several things at once in the same place.

I'd like to know where to use what type of mortise & tenon (M&T) typically used and why each (i.e. is there a reason why to not use one over another). I know there's many more but these seem to be most typical.

• Standard hidden (or blind) M&T - faster/easier than other M&T options for butt joints but not as good for excessive movement of the piece (i.e. chair legs/arms) vs wedged M&T ?
• Stubbed M&T - good for aligning butt joints but not good for lasting strength ?
• Through M&T - good for aligning butt joints and giving a better visual appeal and show more of a craftsman touch as these are more difficult to create w/o gaps showing but not good for lasting strength w/ excessive movement ?
• Wedged Through M&T - same attributes as the through M&T but adds the strength missing but is more difficult to create ?
• Tusk M&T - good adding strength to through M&T and for knock-down connections; also for visual appeal but a little tougher to make ?
• Haunched M&T - good to cabinet doors to hide groves created for panels ?
• Twin M&T - helps with excessive movement of the piece (i.e. chair legs/arms) vs standard M&T ?
• Pegged & Drawbore M&T - helps pull butt joints together tighter for longer lasting connection as well as visual appeal of showing the pegs ?

Thanks for your input as always !

 

[Roy G]

Jeremy, whichever style you choose will depend on how much force you contemplate will act on the finished joint. A small box will not experience much, but a table apron attached to a leg will require a strong joint. A good rule of thumb is keep the mortise 1/3 of the width of the piece it is in. And cut the mortise first so you can fit the tenon to it.

Roy G

 

[JimD]

Jeremy, with modern glues I don't think there is a structural reason for wedged or pinned mortise and tenons. Glue alone is sufficient. But if you like the appearance that could be reason enough. I don't know why you think standard mortise and tenon joints are insufficient for chairs. I've made over 20 that way, some 20 years or more ago, and all work fine. Mortise and tenons are the best joint in my opinion for chairs and table legs to aprons.

I have a domino and my normal form of mortise and tenon is thus a loose mortise and tenon. Two mortises and one tenon glued into both sides. You did not list that type but may want to consider it. You can use a plunge router to cut the mortises if you do not have a domino. I size my tenons as I normally would, not based upon the sizes of pre-made tenons. I make the tenons so they can be any size I need. It's a little bit of a hassle to have to glue up both sides of the joint but it's a lot easier to cut the one loose tenon and to get a great shoulder fit.

 

[mdbuntyn]

The one that you use largely depends on what you build.

I consider stubbed M&T to be the same as locating dowels. There generally isn't enough glue surface for a secure joint.
Through M&T are slightly stronger than a blind M&T, but are mainly a design choice.
Wedging a through M&T offers some protection from glue failure, eliminate gaps, and can add a nice design element if made from a contrasting color.
Tusk M&T were originally for easy disassembly, but now it's largely a design element.
A haunched M&T is more resistant to twisting forces.
Twin M&T are for when then tenon piece is so wide that two smaller mortises is preferable to a single large one.
Pegged M&T offer protection from glue failure, and can be a nice design element.
Drawbored M&T don't require glue, since the drawboring pegs lock the joint together.

 

[jfynyson]

Thanks for the feedback thus far !

@JimD, my thinking on the standard M&T being less strong for chairs is only based off of old chairs I see always need repairs at that joint. However, it's likely as you state that glues these days are superior in strength that their no longer as much an issue (assuming a good fit & glue surface during construction).

 

[Mike Davis]

The one that you use largely depends on what you build.

I consider stubbed M&T to be the same as locating dowels. There generally isn't enough glue surface for a secure joint.
Through M&T are slightly stronger than a blind M&T, but are mainly a design choice.
Wedging a through M&T offers some protection from glue failure, eliminate gaps, and can add a nice design element if made from a contrasting color.
Tusk M&T were originally for easy disassembly, but now it's largely a design element.
A haunched M&T is more resistant to twisting forces.
Twin M&T are for when then tenon piece is so wide that two smaller mortises is preferable to a single large one.
Pegged M&T offer protection from glue failure, and can be a nice design element.
Drawbored M&T don't require glue, since the drawboring pegs lock the joint together.

Dang, you know a lot. Why aren't you teaching somewhere?

 

[Rwe2156]

To add to what Matt said:

Cope and stick doors are stub tenons. They do fine for that, and that's about all.

Wedged thru tenons can actually be structural, for example a shelf with a couple through tenons will add structure to a carcase. Another example is a chair leg that is housed in a seat, such as a Windsor chair.

Tusk tenons are very common in stretchers, and are necessary when a piece needs to knocked down for transport, or example a trestle table.

Draw boring has it's place, such as a breadboard end. Some people pin tenons to imitate an antique as in reproduction furniture.

Historically, draw bored and pinned tenons were frequently done in furniture to add strength, as the only glue then was hide glue and it was sometimes of questionable quality and prone to failure. We could question the quality b/c back then they did not have the refined manufacturing processes, and the "glue factory" used whatever they could get. No doubt the product coming out was not that always consistent.

The glue pot was tended by a shop boy over a fire and no doubt was we could easily conclude it was frequently overheated and denatured. In addition, often joinery that didn't show was more or less hacked out by an apprentice, and the pins gave the master of the shop some "insurance", after all hide glue can only fill to much gap.

And, there was also a lot more wood movement back in the days prior to climate control, so hide glued joints were more prone to failure. In fact, a lot of furniture was made using draw bored tenons and no glue at all.

 

[BML]

I’d agree that it depends largely on what you will be building.

 

[JimD]

I've never seen a failed mortise and tenon joint but I would not be surprised to see one. Chopping a mortise with a chisel is difficult to do well leaving straight sides and a tight fit. Combine that with weak glue and the joint could fail. But a well fitting joint of a reasonable size glued with modern glue has always worked well for me.

The chairs I see failed have all been dowel joints - also apparently glued up with hide glue.

I've made some pretty large raised panel cabinet doors with just the little 3/8 tenon you get with a router table cope and stick bit. But I certainly would not trust tenons of that size for a table leg to apron joint or a joint in a passage door.

 

[Mike Davis]

I bought a screen door for my shop a few years ago. It is made with cope and stick style tenons. Already failed, it sags about 2 inches. Seems like only the screen holding it together now.
After I build the new gates for my fence that will be the next project.

 

[Rwe2156]

The reason dowels fail in chairs is lack of glue surface and rotational instability. Over half the glue surface is endgrain. It has nothing to do with the glue.

Have you all seen the video of drilling a pocket hole deeper and inserting a dowel instead of a screw?

 

[1075tech]

OP, I appreciate your question. As a novice, I had no idea that there were that many types of mortise and tenons.

I've actually learned a lot just by reading up and watching videos about the different types

 

[Jim Wallace]

My understanding is that the drawbored mortise and tenon was designed to deal with wood that was not kiln dried which was the general rule in the 17th and 18th centuries. It was intended to contend with dimensional changes more than with glue failure.

 

[Hmerkle]

@Dee2 is there an article in here somewhere?

 

[Roy G]

Mike, when I need a screen door I always buy L brackets and T brackets to go with it. Screw them on the door and no sag.

Roy G

 

[Dee2]

@Dee2 is there an article in here somewhere?

Maybe. All posters - anyone up to drafting a M&T how-to article? I'll help with editing.

 

[jfynyson]

Maybe. All posters - anyone up to drafting a M&T how-to article? I'll help with editing.

I'd love to have one of those but I'm certainly not qualified to assist in writing. I do believe the various woodworking books I have do not do this subject justice while the Wood Whisperer's book on Joinery seems to be the closest.