# Using a full thickness of a board as the tenon? (not cutting a tenon into the end)



## Jimothy (Oct 29, 2015)

I'll admit, the first time I did this I was a novice. I understand traditionally you cut a mortise and then create a tenon that fits in by sneaking up on it until it fits nicely. What would be the harm in just sneaking up on the actual thickness of the board itself to fit into the mortise? You could easily do this with a drum sander taking small increments until the fit is good.

Is there a reason we spend time cutting a tenon into the end instead of just using the board itself? I guess if youre using very thick stock then your mortise would have to be very big to accomodate that, but are there any other reasons why this is a big no no ?

Thanks!


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## Lazyman (Aug 8, 2014)

There may situations where that would work but part of the strength of a mortise and tenon joint is the shoulder of the tenon fitting tightly against the joining board.


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## Jimothy (Oct 29, 2015)

I didnt think of that, but isn't that part basically just an end grain joint?


> There may situations where that would work but part of the strength of a mortise and tenon joint is the shoulder of the tenon fitting tightly against the joining board.
> 
> - Lazyman


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## Sylvain (Jul 23, 2011)

> There may situations where that would work but part of the strength of a mortise and tenon joint is the shoulder of the tenon fitting tightly against the joining board.
> 
> - Lazyman


+1
I would add, if one look at tusk tenon assembly (with a little slack in it to allow knock down) while the key secure the assembly, the tenon shoulders are ensuring the correct geometry of the assembly *and absence of rocking*.
(the same for assemblies with bed bolts)









As there is no glue in a tusk tenon assembly, the question of end grain isn't relevant.
In a glued assembly, it is mainly the glue on the tenon cheeks that keeps the pieces together.

Have a look at Paul Sellers method for (nearly) guaranteed mortise and tenon fitting:





Now instead of making shoulders the traditional way, one could glue shoulders.
I only know one implementation of this idea:
https://theapartmentwoodworker.com/2021/10/16/something-refreshing/

Keeping the pieces together and ensuring correct geometry/absence of rocking are two different functions.


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## wapakfred (Jul 29, 2011)

Not trying to be a smartarse (really) but the best way to find out it's a bad idea is to go ahead and try it. That shoulder is a very functional part of the joint, though it isn't glued or fastened.


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## RClark (Jun 1, 2012)

> There may situations where that would work but part of the strength of a mortise and tenon joint is the shoulder of the tenon fitting tightly against the joining board.
> 
> - Lazyman


Very true. That shoulder, particularly on the bottom end of the joint, is transferring weight forces from above the joint to the structure below. It also resists racking action from lateral forces.

Depending on the project, the lack of the shoulder could weaken the joint over time.

The perfect fit without cheeks/tenons has a very small margin of error. I suppose it could be easy to sneak up on the fit and get a tight joint line. However, in practice, I think getting a clean line is probably easier with cheeks and tenons. The actual mortice and tenon fit being concealed allows for a wider margin of error, and a poor fit can be easily remedied without impacting the clean look on the outside of the joint.


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## Sylvain (Jul 23, 2011)

Further than being structurally important as explained above, 
the shoulders also serve as abutment when clamping everything together during glue-up.
They allow precise form and dimension.


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## splintergroup (Jan 20, 2015)

All good points.

Another is a general rule of thumb that the tenon is about 1/3 the thickness of the mortised wood. You need enough "meat" in the walls of the mortise or else they can break if torqued.


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## bondogaposis (Dec 18, 2011)

The shoulder on the tenon prevents racking and since tenons are the easiest to cut part of a mortise and tenon joint, there is not much point in avoiding them.


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## Sylvain (Jul 23, 2011)

> [...] since tenons are the easiest to cut part of a mortise and tenon joint, there is not much point in avoiding them.
> 
> - bondogaposis


+1 The mortise has its role in the geometry. A sloppy mortise will conduct to a warped frame.

In addition to the tusk-tenon and bed-bolt assemblies, I should have also mentioned pegged mortise and tenon (without glue).


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## HorizontalMike (Jun 3, 2010)

IMO, is to skip cutting tenons on the "end" of a board. After I started using floating tenons, I never looked back.

First, what ever setup you use to cut your mortise correctly,... use that same method to cut another mortise into the other board to be joined. That way both your mortises will match (be centered).

Second, cut your tenon(s) from a long piece of stock, plane it to proper width and thickness, then start cutting individual floating tenons to fit. I sometimes have to actually cut a small groove into the side of the tenon in order to get the glue to flow out, because these tenons can be mated so tight that the excess glue gets stuck in the mortise making nearly impossible to seat the tenon completely.

Just my 2-cents…


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## Sylvain (Jul 23, 2011)

HorizontalMike,
That might be true when using machinery but not for hand tool only.
The OP doesn't say how he works.

Going in that direction, there are also dowels and biscuits.
I have used floating tenons for repair.
One can create shoulders like in "the apartment wood worker" link above which is a variation of laminating boards together as frequently used in workbench building.

Answering the OP question,
The final conclusion remains tenon shoulders are very highly recommended whatever the form/nature of the tenon or the way to create shoulders.


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## LittleBlackDuck (Feb 26, 2016)

Get a *ROTEX*!


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## MarkCh (Jul 7, 2020)

The shoulders can be cut precisely on the ts and hide any goofs on the mortise


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