# Tenon joint question



## Novicesaw (May 8, 2011)

I have to cut a tenon for three slats in the back of my mission dining chair. I have seen some people round off the tenon and some square off the mortise does it Matter which way it is done?:help::help:


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## mdntrdr (Dec 22, 2009)

Square is traditional, I've never done round.

It's up to you, wich you prefer. :smile:


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## Locodcdude (Oct 24, 2010)

To me I don't think it matters, But I'm sure other die hard Mortise and Tenon guys here would LOOOOVEEEE to differ. I typically do what ever is easier at the time. If the mortise is shallow, I'll just square it up, if it's deeper, I'll round the tenon.


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## Novicesaw (May 8, 2011)

How long (deep) should the tenon's be if the rail is 2 inches wide and how wide would you make the tenon if the rail is 3/4 thick?


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## mdntrdr (Dec 22, 2009)

Novicesaw said:


> How long (deep) should the tenon's be if the rail is 2 inches wide and how wide would you make the tenon if the rail is 3/4 thick?


A basic rule of thumb is... tenons are 1/3 width of stock and length is 5 times width.

This can't always be achieved with thinner legs etc., but with todays glues it usually isn't a problem. :smile:


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## cabinetman (Jul 5, 2007)

mdntrdr said:


> A basic rule of thumb is... tenons are 1/3 width of stock and length is 5 times width.
> 
> This can't always be achieved with thinner legs etc., but with todays glues it usually isn't a problem. :smile:


+1 (with a caveat). Some tenons can't be of a specific length, as in stub tenons. There's not much stress on those slats and the M&T even with a tenon that may not be that long will be more than adequate if fitted well. 

Since your slats may be rectangular or square, the shoulder of the tenon will appear as a rectangle or square, but the tenon could be either rectangular or square. For round, the same theory for the tenon can apply. IOW, it doesn't really matter. 











 







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