# tenon shoulders on the edges



## gj13us (Apr 19, 2016)

I was watching Paul Sellers' videos about mortise and tenons, and noticed that when he cuts a tenon he cuts shoulders only on the face of the wood. He doesn't cut shoulders on the edge grain. Any idea why? Given my skill level, if I can get away without cutting the edge-side shoulders, all the better, because they otherwise increase the chances that something will go wrong. Too many degrees of freedom, as it were.


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## epicfail48 (Mar 27, 2014)

Id say its probably because for a lot of cases it just isnt needed. The faces need to be cut because the tenon has to fit into a mortise in an equally thick piece of wood, but its pretty seldom youre joining 2 pieces the same width, so no need to narrow the width. Saves time and effort, and you arent really losing anything if the joinery allows for it


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## woodnthings (Jan 24, 2009)

*My "theory" .....*

The reason is that a shoulder does two things. It prevents racking in one or both planes at 90 degrees and it "hides" a mortise that may be less than perfectly cut. The face is the wider surface typically, unless the part is square, so it is most resistant to racking. Chair legs and table aprons are the most common applications where racking is an issue and extra strength is required. 

A discussion of this topic here:
https://www.woodworkingtalk.com/f9/tenon-shoulders-trestle-table-stretcher-88305/


As others have suggested, it may not be required and it would save time and effort if done with hand tools. However, I have made tenons using the bandsaw with depth stops on the fence which goes extremely quickly.


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## Steve Neul (Sep 2, 2011)

Unless you are building a rack to store concrete on I don't see the point of making a shouldered joint. The shoulder is there to hold any vertical weight on the rail so all the weight wouldn't be on the tenon. Why make an unsightly joint that most people wouldn't understand being there in the first place?


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## gj13us (Apr 19, 2016)

Thanks for the answers. After I posted here, I thought someone might say, 'Why ask us? Why not ask him?'. So I did. And they answered. The answer is that both types of tenon are acceptable. The edge shouldered tenon is used for finer furniture to help hide the joint


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## FrankC (Aug 24, 2012)

gj13us said:


> Thanks for the answers. After I posted here, I thought someone might say, 'Why ask us? Why not ask him?'. So I did. And they answered. The answer is that both types of tenon are acceptable. The edge shouldered tenon is used for finer furniture to help hide the joint


Good for you, it was an opinion they had so good to hear their logic, wish more people did that.


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## DrRobert (Apr 27, 2015)

> Unless you are building a rack to store concrete on I don't see the point of making a shouldered joint. The shoulder is there to hold any vertical weight on the rail so all the weight wouldn't be on the tenon. Why make an unsightly joint that most people wouldn't understand being there in the first place?


I don't understand this. The tenon would be holding vertical weight, the shoulder is there to add strength. Basically the function of a tenon is to hold two intersecting pieces of wood together. It is arguably the oldest ww'ing joint known.

Haunched tenons add some strength, however if the tenon is fitting well, not much. 

The main place to use one are door frames, or top of a leg to accept an apron. In a case where racking is a concern, best way to strengthen a M/T joint is to pin it. 

FWIW, generally usually make at least a 1/8" haunch on any tenon, , mainly because I don't have to be as precise with my joinery and worry about a gap showing.


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## gj13us (Apr 19, 2016)

I'll add another question: 

If I'm joining a 2x4 rail to a 4x4 stile, I don't have to cut shoulders at all? I can cut a 1 1/2" x 3 1/2" mortise into the 4x4 and just shove the 2x4 into it? Let's say this is for a garden trellis, or garden gate, or workbench. (i.e., not for a roof or another structure where long-term safety is a consideration).


I guess this should be obvious to even the most novice woodworker, and the question shows the depth of my knowledge deficit. Sometimes I've got negative knowledge.


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## FrankC (Aug 24, 2012)

Every situation is different, your example of fence construction is not in the same category as bench or table construction. In short you use the appropriate joint for the job.


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## woodnthings (Jan 24, 2009)

*You could ... but don't do it !*



gj13us said:


> I'll add another question:
> 
> If I'm joining a 2x4 rail to a 4x4 stile, I don't have to cut shoulders at all? I can cut a 1 1/2" x 3 1/2" mortise into the 4x4 and just shove the 2x4 into it? Let's say this is for a garden trellis, or garden gate, or workbench. (i.e., not for a roof or another structure where long-term safety is a consideration).



First off, you would take 1/2 od the structure from the 4 X 4.
Second, the shoulders prevent racking in the direction/plane of the face. Once it's glued or pinned in place, you can't move the opposite end up or down because the shoulders prevent it. Shoulders add a great deal of strength. 



:vs_cool:


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## FrankC (Aug 24, 2012)

One way to build a fence is to cut through mortices in the posts (4X4's) set the posts, measure 2X4 rail to length mid point between posts and cut to length. Rail is pushed through far post and pulled back into near post. Advantage is ease of assembly, and you don't have a shoulder on the rail trapping moisture.

This has no relation to furniture making which is another topic entirely.


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