how should I size tenons?

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Forum topic by JesseTutt posted 11-03-2012 03:43 AM 1605 views 0 times favorited 4 replies Add to Favorites Watch
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854 posts in 2528 days

11-03-2012 03:43 AM

Topic tags/keywords: question mortise and tenon sizing a tenon

I am going to build a new workbench this weekend. I plan to use existing 2×4s that I have on my wood rack. I need to get rid of them and make space for “real” wood. I was going to mortise and tenon joinery. My plan calls for through tenons on the horizontal rails connecting the front left leg to the rear left leg. The top joint will actually be a bridal joint and the lower a through tenon.

Assuming that the 2×4 is actually 1.5×3.5 I am planning on making a 1×3 tenon.

My question is “Are there any rules on how to size a tenon?”

-- Jesse, Saint Louis, Missouri

4 replies so far

View pintodeluxe's profile


5949 posts in 3231 days

#1 posted 11-03-2012 03:46 AM

Tenons are usually 1/3 the thickness of its stock. IE 1/2 tenon for a 1-1/2” board, although a little fatter is also acceptable. I usually plan for mortise sizes that correspond to my hollow chisel sizes 1/4”, 5/16”, 3/8”, or 1/2”.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View John's profile


47 posts in 2491 days

#2 posted 11-03-2012 05:53 AM

The 1/3 rule applies more to the piece that gets the mortise. ie, if you’re joining two pieces of 3/4” stock, you’d make the joint parts 1/4” thick so you leave enough meat around the mortise that it doesn’t split or blow out. If you don’t have to worry about the mortised piece, then the bigger the tenon, the better, as long as you leave enough shoulder to firmly register the joint.

So for a 2×4 going into a mortised 4×4, a 1×3 tenon is fine. Same if it’s going into the wide side of a 2×4.

View Woodknack's profile


12842 posts in 2798 days

#3 posted 11-03-2012 06:15 AM

Hmm, I’ve always made my mortises 1/2 the stock (or closest chisel size), so a 3/8 mortise in 3/4 stock. Maybe I’ve been making them too big?

-- Rick M,

View cutworm's profile


1075 posts in 3211 days

#4 posted 11-03-2012 10:56 AM

I’m told that the tenon length should be twice the tenon thickness.

-- Steve - "Never Give Up"

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