Floating vs Fixed Tenon Joinery

[Edward P. Surowiec]

Are Floating Tenons as strong as the conventional fixed Tenons??

I am making window frames for a garden shed. The frames are made with 6/4 stock and measure 35X30; they will pivot out on three hinges similar to a door. The corner joints will be mortise and tenon.

I am concerned about the strength of the tenons. Are floating tenons a good choice for my application?

Thanks Ed

[Dave Cohen]

From what I understand they are not as strong, but they still may be plenty strong for what you are trying to do.

[Jamie Buxton]

Think about it this way...

If you make a non-floating tenon, you're depending on glue to hold the joint together. The glue is on the cheeks of the tenon and the walls of the mortise. If you make a floating tenon, you're depending on glue to hold the joint together. The glue is on the cheeks of the floating tenon, and the walls of both mortises.

What's the difference? I can't see any.

[Justin Bukoski]

Ed, they are close enough in strength to not have to worry about it.

[Doug Shepard]

Check out the current issue of Wood magazine. They have a joint torture test and simple half-laps came out vastly stronger than M&T's if you're just aiming for the strongest joints.

[John Emmerson]

You may find this link useful.
http://www.youtube.com/watch?v=EgSPbTfJ_Xc
It's a video by Steve Muskery where he conducts tests between conventional and loose mortise and tenon joints.
John

[Chris Friesen]

Check out the current issue of Wood magazine. They have a joint torture test and simple half-laps came out vastly stronger than M&T's if you're just aiming for the strongest joints.

Unfortunately none of these articles address long-term usage. I'd like to see a forced-aging test with thousands of load/unload cycles, humidity/temperature variations, etc.

I'd buy that half-laps are strongest right after they are made, but I doubt that they would last as well over time. At least with a mortise and tenon you have the option of wedging or pinning/drawboring the joint so that you're not relying entirely on the glue.

[Jim Becker]

IMHO, I seriously doubt there is any difference in strength between fixed (traditional) tenons and loose tenons, especially with today's modern glues. In fact, you also have the option of using a stronger material for the tenon if you prefer as long as you take into consideration wood movement if the tenons are "large" in size.

[Ellen Benkin]

I use floating tenons a lot. Since a glue joint is usually stronger than the wood it surrounds, I've assumed that having both ends of the tenon glued makes it at least as strong as a tenon that is part of a part.

[Gary Keedwell]

Unfortunately none of these articles address long-term usage. I'd like to see a forced-aging test with thousands of load/unload cycles, humidity/temperature variations, etc.

I'd buy that half-laps are strongest right after they are made, but I doubt that they would last as well over time. At least with a mortise and tenon you have the option of wedging or pinning/drawboring the joint so that you're not relying entirely on the glue.
I was going to say the same thing as Chris ...so I'll just second what he said. Undoubtedly, glues are better....but they are not forever....I want something mechanical in my joints.

Gary

[Mark Singer]

The strength is the same. The floating method is usually easier. There are also advantages in eliminating cracking at joints since the wood of the main member is removed you are creating more stability. More like plywood ...
I think all woodworkers should learn the traditional techniques of M & T construction though. Since there is long grain to long grain contact in a floating tenon joint the tenon joinery connection is very strong!

[Randy Klein]

I was going to say the same thing as Chris ...so I'll just second what he said. Undoubtedly, glues are better....but they are not forever....I want something mechanical in my joints.

Gary

And I will second your comment, which I guess is "thirding" Chris's...

[Mark Singer]

IMHO, I seriously doubt there is any difference in strength between fixed (traditional) tenons and loose tenons, especially with today's modern glues. In fact, you also have the option of using a stronger material for the tenon if you prefer as long as you take into consideration wood movement if the tenons are "large" in size.

You have a good memory:rolleyes:

[Nate Rogers]

Both are incredibly strong, usually chose one over the other based on how easily I can accomplish the task....Do whatever you are more comfortable with, don't worry about it.

Nate

[Alan Schwabacher]

Over time, most of the glue release would be expected at the crossgrain join common to both traditional and inserted tenon. As long as the tenon is constructed of wood with similar expansion and grain orientation as the part it's inserted in along the grain, there will be little or no added stress on expansion and contraction. So I'd expect the differences between traditional and inserted tenons to lessen over time, while the advantages of mortise and tenon joints over other joints would probably increase over time.

Drawboring is another story, that helps very much in assembly and in holding joints tight. These things are usually more important than sheer strength, which may actually be decreased by the drawbore, if the joint is well fitted and glued. Joints are rarely stressed to the point of complete failure though; holding together long enough to be fixed after glue eventually fails from fatigue and moisture cycling is a more realistic goal, and where M&T excels.

[Edward P. Surowiec]

Thanks everyone for your comments and suggestions. Please excuse my late reply, I've been on the road.

Happy Holidays, be well and enjoy.
Ed:)