The Width of a Tenon

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Forum topic by bruc101 posted 01-11-2010 04:55 AM 2073 views 0 times favorited 5 replies Add to Favorites Watch
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1075 posts in 2959 days

01-11-2010 04:55 AM

Last night in our guild meeting a question was asked by someone about the max width a tenon should be.
He through out a 4 1/2” board width x 3/4” long tenon. I was amazed at all the answers and suggestions that came out of it. I would like to get your opinions on this.

-- Bruce Free Plans

5 replies so far

View bill1352's profile


130 posts in 2539 days

#1 posted 01-11-2010 05:00 AM

personally for a 4 1/2 wide board that is 3/4 thick i’d want a 2 1/2 long tenion thats 3/8ths thick. bigger the better.

-- Keep Your Stick On The Ice

View Scott Bryan's profile

Scott Bryan

27251 posts in 3240 days

#2 posted 01-11-2010 03:00 PM

With M&T joinery the strongest joint is produced by using a tenon that is 1/3 the width and length of the board. For a 4 1/2” board that is 3/4” wide this would yield a tenon that is 1/4” in width and 1 1/2” in length.

-- Challenges are what make life interesting; overcoming them is what makes life meaningful- Joshua Marine

View stefang's profile


15512 posts in 2752 days

#3 posted 01-11-2010 07:29 PM

I think Scott pretty well nailed it. However there are lots of exceptions/compromises when design is the overruling factor. Also, strength isn’t only a mortise size issue. The amount of glue service also has something to do with it. Here I’m thinking of double tenons and probably other variations as well. It is an interesting subject, so it would be interesting to hear more discussion about it.

-- Mike, an American living in Norway.

View TheDane's profile


4930 posts in 3081 days

#4 posted 01-11-2010 08:59 PM

I go with Scott on this … a 3/8” tenon in a 3/4” board means mortise walls that are only 3/16” thick.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View bruc101's profile


1075 posts in 2959 days

#5 posted 01-11-2010 11:04 PM

Interesting answers guys. I also forgot to mention the 4 1/2” board would be going into a 3/4” x 2 ” face frame.

-- Bruce Free Plans

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