A question about loose tenons

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Forum topic by RockyTopScott posted 04-05-2009 01:34 PM 1419 views 0 times favorited 11 replies Add to Favorites Watch
View RockyTopScott's profile


1186 posts in 4041 days

04-05-2009 01:34 PM

Topic tags/keywords: joining

I am using loose tenons to construct face frames.

The final depth of the wood will be as close to 3/4” as my planer and calipers can get.

My question is what size mortise is recommended? I am considering 3/8” and have read some about sizing integral tenons but not so much loose tenons.

I notice in the Domino videos that the mortise it produces is not that wide. I will be using a router and upcut bit to do mine.

Any suggestions from the more learned LJs out there?


-- “When you want to help people, you tell them the truth. When you want to help yourself, you tell them what they want to hear.” ― Thomas Sowell

11 replies so far

View tenontim's profile


2131 posts in 4307 days

#1 posted 04-05-2009 03:29 PM

My choice is to use a 3/8” tenon on 3/4” material. The width will be determined by the width of your frames. Leave enough wood on the end, so that you don’t have a weak spot that will break. It’s a good idea to leave the excess, dog ears, on the end of your frame pieces, until you’re all glued up, then cut to length.

View araldite's profile


188 posts in 3966 days

#2 posted 04-05-2009 05:18 PM

My understanding is the tenon should be 1/3 the thickness of the stock being mortised. In your case, I would go with 1/4” as DaveR recommends. As the mortise gets bigger, it weakens the mortised stock. Having said that, for face frames I doubt if it makes much difference since it will be attached to the body of the project where it will get most of its strength. It’s not a load bearing joint.

-- Failure is the road to success if you learn to learn from your mistakes - Vince, Greenville, SC

View kolwdwrkr's profile


2824 posts in 4152 days

#3 posted 04-05-2009 07:08 PM

I agree with DaveR and araldite. But I also wonder why you chose loose tenons for the joinery. Why not biscuits? Pocket screws? araldite is correct when he said it is not a load bearing joint and loose tenons would be overkill. But, having said that, it is good experience, will make a strong frame, and the project will be an heirloom. I am anxious to see this in the projects section. Good luck

-- ~ Inspiring those who inspire me ~

View Francisco Luna's profile

Francisco Luna

969 posts in 3956 days

#4 posted 04-05-2009 07:29 PM

That number comes from the mortise chisels you have for the task, or drill bits if you are using a press drill~mortiser. 1/4”, 5/16”, 3/8 would be fine, Titebond III make wonders!

-- Nature is my manifestation of God. I go to nature every day for inspiration in the day's work. I follow in building the principles which nature has used in its domain" Frank Lloyd Wright

View Waldschrat's profile


505 posts in 3998 days

#5 posted 04-05-2009 07:33 PM

Dave and the rest are right, 1/3 is the standard! go with that!

-- Nicholas, Cabinet/Furniture Maker, Blue Hill, Maine

View RockyTopScott's profile


1186 posts in 4041 days

#6 posted 04-05-2009 09:45 PM

kolwdwrkr hit the spot..this is my first real project (kitchen cabs) and I want the experience of doing loose tenons for future reference.

I think I am going to use the 1/4” with TiteBond III and see how it works.

If I miss, it surely won’t be my last mistake. I am hopeful to learn from reading this site and practice practice practice.

Tenontim, I never thought about the dog ear concept but will try that as well.

The cabs, frames and doors will be cherry and I am considering a Maple countertop, so I will be back for guidance on that in the future.

thanks to all for your responss. Scott

-- “When you want to help people, you tell them the truth. When you want to help yourself, you tell them what they want to hear.” ― Thomas Sowell

View Karson's profile


35209 posts in 4963 days

#7 posted 04-05-2009 09:59 PM

1/3rd the thickness/

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Appomattox Virginia [email protected]

View tenontim's profile


2131 posts in 4307 days

#8 posted 04-06-2009 12:01 AM

Not saying anyone is right or wrong. I guess I went to an older school of thought than most of these guys.
The “old school” says the sides of the mortise added together should equal the thickness of the mortise, other wise you have a weak tenon. So that makes the tenon half the thickness of the piece, not a third. It probably doesn’t make any difference on face frames. Once they’re attached to the case they don’t have any stress on them anyway. You just might want to do some more research into joinery layout before you build anything that is going to be stressing the joints.
That’s my old $0.02 worth.

View Eduardo Rodriguez's profile

Eduardo Rodriguez

37 posts in 3933 days

#9 posted 04-06-2009 08:16 PM


-- Tempus fugit...better work wood!!!

View tenontim's profile


2131 posts in 4307 days

#10 posted 04-07-2009 06:04 PM
January/February 2009 Fine Woodworking, for you magazine readers. This will give you some probable doubt.

View Julian's profile


884 posts in 4088 days

#11 posted 04-07-2009 06:36 PM

For a face frame, there is no reason to have a m/t joint more than 1/3 of the total thickness. In most cases when you make a m/t joint in cabinet door, your mortise will be the same as the groove for the panel which is 1/4”.

-- Julian, Homewood, IL

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