# Mortise and Tenon Question



## ScottyB (Mar 1, 2009)

I have not done any M&T joinery before but have a couple projects in my future where I would like to. The Tenon seems fairly straight forward but I am wondering if there is a formula or guideline as to how big the tenon should be in relation to the material used. Also, I do not have a mortising tool but I do have a router. When making mortises with a router do you just square up the ends with a chisel or is there a better way? Does it work to chamfer the corners on the tenon instead? Yes, I'm looking for easy, but not at the expense of the joint.


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## johnv51 (Oct 27, 2008)

I've rounded the corners of many a tenon going into a router made mortise. You'll be fine. Keep your mortise and tenon width to no more than a third of the width of the stock.


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## Willie T (Feb 1, 2009)

John's right. Clip off the corners of the tenons with a chisel. Leave the mortises alone.


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## Tony B (Jul 30, 2008)

Generally, a mortise and tenon is 1/3 to 1/2 the thickness of your stock. 
If you are using 3/4" stock, 1/3 would be 1/4" which is way too thin. 
For 3/4" stock, use 3/8" mortise and tenon which is 1/2 the thickness of your stock. 

If you are using a router to make the mortise and your tenons are rectangular, it is much easier to use a chisel and round out the tenons than it is to square up the mortise.


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## ScottyB (Mar 1, 2009)

I forget my manners. Thank you for the help on this. I really appreciate it.


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## Chiefwoodworker (Jul 17, 2008)

Fine Woodworking did an article on the strength of various joints and no surprise the M & T won big time. But they pointed out that thicker tenons were stronger. This is true because the thicker tenon provides more shear strength. But the M & T is so strong to begin with that the increased strength of the thicker tenon was sort of moot. In 3/4" stock either a 1/4" or 3/8" is fine. More important is to get a snug but not overly tight, or worse, loose fit.


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## Tom5151 (Nov 21, 2008)

just did a whole bunch of M&T on a couple of tables....

I cut the mortisies with a plunge router and a 3/8 upspiral bit. I used a homemade jig to position the router.

I used 3/4 stock and made the tenon 3/8 thick. I did them on the TS with a stacked dado. Then took a very sharp chisel and beveled the corners of each just enough to fit into the mortise......

everything fits nice and tight and was really pretty simple to do....

if you do need to tune the fit I'd proabably tune the tenon as opposed to the mortise...just my opinion......


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## Chiefwoodworker (Jul 17, 2008)

Tom5151 said:


> just did a whole bunch of M&T on a couple of tables....
> 
> I cut the mortisies with a plunge router and a 3/8 upspiral bit. I used a homemade jig to position the router.
> 
> ...


Your opinion is correct. Also, mill the mortises first. Then cut the tenons to fit snug. Creep up on the tenon thickness (creep down actually) to get a really good fit. A shoulder plane id good for this.


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## Tom5151 (Nov 21, 2008)

Chiefwoodworker said:


> Your opinion is correct. Also, mill the mortises first. Then cut the tenons to fit snug. Creep up on the tenon thickness (creep down actually) to get a really good fit. A shoulder plane id good for this.


oh...and make sure to have plenty of stock the EXACT thickness of the boards you are cutting the tenons from so you can make test cuts and sneak up on the thickness as has been mentioned. It won't do you any good to use scrap of a different thickness to makes test for tenon thickness. If you do that and then transfer those settings to your production work you will find out like I did,.....:blink::thumbdown:... that your tenons will mysteriously be too thin or too thick and you'll spend countless hours trying to figure out why......LOL


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## Chiefwoodworker (Jul 17, 2008)

Tom5151 said:


> oh...and make sure to have plenty of stock the EXACT thickness of the boards you are cutting the tenons from so you can make test cuts and sneak up on the thickness as has been mentioned. It won't do you any good to use scrap of a different thickness to makes test for tenon thickness. If you do that and then transfer those settings to your production work you will find out like I did,.....:blink::thumbdown:... that your tenons will mysteriously be too thin or too thick and you'll spend countless hours trying to figure out why......LOL


I agree completely. That could ruin a whole day. A week maybe.


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## Tom5151 (Nov 21, 2008)

Chiefwoodworker said:


> I agree completely. That could ruin a whole day. A week maybe.


oh it sure could...it sure could......:wallbash:


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## Verndog (Jan 19, 2009)

There is some very good advice on numerous other posts in this area on M&T joints. Someone had a link on this forum or maybe it was another that covered complete descriptions of the joint with size requirements, with through explanation of cheeks, shoulders. loose tenon etc. I think the link was to woodworkers journal but the link I have doesn't seem to work any more. I wish I could find it again, maybe if someone has seen it they could post it.
Good Luck
Vern:smile:


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