Please school me on tenons

[Frederick Skelly]

Hi guys,
The infamous butcher block project continues. I've cut the mortises for the aprons and I'm now making the split tenons. Never used split tenons before, so tonite I made a bunch of practice joints to get the hang of it. (Am using backsaws, but what I'm asking is generic to which type tools.) The 3" tenon is cut into two
1 1/4" wide tenons, with 1/2" between them. I dont know what to call the two "halves" of that split tenon, so I'll call them each a "half tenon", for this post.

1. Should I undersize each of the half tenons about the width of a saw kerf for expansion? Or is that a waste of time? Different books/articles say conflicting things. IMO, one end of each half tenon better fit flush against one end of the mortise or the joint won't be as strong as it could be.

2. I normally use Tightbond 2 for M&T joints, but the butcher block will get banged on, bumped, etc (it's a butcher block, right?). Should I go down to the hardware store and get some 60 minute epoxy? Or is that overkill in a well fitted M&T joint?

As always, thanks for your advice and experience.
Fred

Edit: I may have misused the term split tenon. The right one might be double tenon. If so, please pardon my ignorance. There's a pic below in post #5.

[Jerome Sidley]

I used Split tenons on my bench I cut the tenons the same width as you normally do, cut the slots installed and hammered in the wedge I did not use any glue and they (the legs) are still tight and the bench get a heck of a lot of banging more than a butcher block I would imagine.

[Mike Cutler]

1. Should I undersize each of the half tenons about the width of a saw kerf for expansion? Or is that a waste of time? Different books/articles say conflicting things. IMO, one end of each half tenon better fit flush against one end of the mortise or the joint won't be as strong as it could be.

The tenon is not a clamp. It is the glue in the joint that is doing the work.The tenon is the mechanical method that the joint gains strength.There are tenons, such as the foxtail tenon,a and a through drawn tenon where the tenon is the both the mechanical strength and provides the joint strength, but in the tenon you are using it is not. It is the adhesive that will hold the joint together.

2. I normally use Tightbond 2 for M&T joints, but the butcher block will get banged on, bumped, etc (it's a butcher block, right?). Should I go down to the hardware store and get some 60 minute epoxy? Or is that overkill in a well fitted M&T joint?

If it's not going to get wet, or require the use of powerful cleaning agents, Titebond should be more than adequate. The adhesion strength of epoxy and Titebond is about the same at 4000psi. One concession you could make is to pin the joint if at all possible.

As always, thanks for your advice and experience.
Fred

I think you'll be fine gluing up what you have. It sounds as if you've thought it out well. Don't succumb to "paralysis, by analysis". ;)

[Frederick Skelly]

Thanks guys!

[Brian Holcombe]

What's the point of doing a split tenon? Having a 1/2" of short grain between them seems like a recipe for disaster? I use double tenons regularly, but I can't see the purpose of a split tenon.

[Frederick Skelly]

What's the point of doing a split tenon? Having a 1/2" of short grain between them seems like a recipe for disaster? I use double tenons regularly, but I can't see the purpose of a split tenon.


Brian, maybe I used the wrong term. Here's a pic of what I'm doing. Is this a split tenon or a double tenon? I'd value any advice you can give me. What I've read led me to believe this approach would reduce wood movement that could cause joint failure (though many people use 3" tenons without issue). But that was my thinking.
361334

Thank you!
Fred

[Brian Holcombe]

On wider stock I often make double (side by side) tenons. 3" is not wide enough to cause concern and that short area between the tenons is liable to cause grief. It reduces the effective glue surface as well. If I can be frank, I would discontinue this practice in smaller tenons.

[Bill McNiel]

On wider stock I often make double (side by side) tenons. 3" is not wide enough to cause concern and that short area between the tenons is liable to cause grief. It reduces the effective glue surface as well. If I can be frank, I would discontinue this practice in smaller tenons.

J'accord. x

[Jay Aubuchon]

3" is not wide enough to cause concern and that short area between the tenons is liable to cause grief.

How wide would be enough to cause concern? 4"? 5"? More?

Asking for a friend.

[Brian Holcombe]

How wide would be enough to cause concern? 4"? 5"? More?

Asking for a friend.

It depends on a host of factors. Most often I use rift sawn material for rails, stiles and frame members. On a large tenon I would likely do something like a keyed through tenon so that I could leave a gap above the tenon to allow some movement.

Furthermore wood compresses across the grain, some more than others.

[Jay Aubuchon]

On a large tenon I would likely do something like a keyed through tenon so that I could leave a gap above the tenon to allow some movement.

How about on a door or gate?

[Andrew Hughes]

I thought you were taking about splitting a tenon with a wedge of a wedge tenon.Glad I didn't respond.

Ive seen that tenon with the middle missing.When I took apart some old doors for the wood they lasted a very long time and held together well.So I do the same when they are wide like that.

[Brian Holcombe]

How about on a door or gate?

A split tenon still expands as a whole, if I needed to make a tenon especially large I would work everything in my favor; IE use draw bored M&T....not glued solid and use radial grain (rift and VG) of a wood that doesn't move that much.

On the bottom rail, I might be so inclined to make the tenon 4-5" tall and the remainder would be a haunch (floating stub tenon).

Use your judgement and planning, depends on the many factors previously mentioned.

[Jerome Sidley]

I also thought you were speaking of a wedged tenon please strike my remarks from the record.

[Frederick Skelly]

I also thought you were speaking of a wedged tenon please strike my remarks from the record.

Yeah, that was my bad Jerome. Thanks for trying to give me a hand.
Fred

[Frederick Skelly]

Thanks again to all of you. I appreciate the advice!
Fred

[Robert Engel]

You can make a slight taper to the mortise, maybe 2° or like 1/16" wider tapering down to nothing at the bottom.

This give room for the wedges to expand the tenon and gives even more strength to the wedge joint.

I think this would be a good idea in your application.

Yes, I would use epoxy glue, also for waterproof qualities. Personally I don' think TBIII is as "waterproof" as you might think.

[Prashun Patel]

I would have no reservation making the two 1 1/4" tenons snug in their respective mortises.

How thin are your legs. I think the double mortise has the positive effect of not requiring such a large void in the leg.

[Frederick Skelly]

Thanks Robert!
Thanks Prashun! The legs are 3 1/2" square. So the tenons are each 1 1/4" long x 1/2" wide. I've got nearly all of them cut and Im pleased with the fit - snug but not "pound in" tight. The shoulders fit well. I've gotten better at sawing too - an added bonus!