Tenon question

[Michael Hammers]

I am in the hopes of trying to get some input on a really long shot question...
I was looking at alternatives for big thru tenons and found a picture in Andy Raes book "choosing and using hand tools".
Anyway there is a section on holding work that shows a wedge tenon that fits over the tenon and not thru it. It is shown on the construction of some shopmade horses.

Just curious if anyone has seen it and if you think it would be structurally sound?
I like that idea better than boring thru and weaking the piece..

I will be honest, I have been stalled on this part of my bench build because quite frankly I am unsure of myself.
I fear that I will blow the sides of my rails out if I bore thru it...
Any help would be great...
Thanks

[Lucas Bittick]

I have never built a joint like this, but if the mortise/tenon is constructed like so, then I imagine it is pretty robust:

[Chris Friesen]

That looks like it's shaping into a sweet bench base. I like it.

The general idea you describe makes sense, it would be sort of like an inside-out tusk tenon. It might be a bit harder to make the wedge; assuming it wedges on both sides it would have to be about as thick as the tenon itself and I'd worry about breaking it at a weak point when pounding it into place.

I'd probably go ahead and bore through the tenons vertically for a standard tusk tenon. Take it slow and you shouldn't have any problems blowing out the side. Even if that does happen, it's only a cosmetic blemish and it will still function just fine.

If you think about the mechanics of a tusk tenon joint, the sides of the mortise where the wedge fits are only there to transfer tension from the wedge to the rest of the stretcher. Wood is really really strong in tension, so that generally won't be a weak spot. The critical part of a tusk tenon joint is the wood on the outer ends of the stretcher. The wedge is pushing outwards, and if there isn't enough material there it could shear the chunk of endgrain right out of the stretcher.

If you really don't want to mortise the tenon vertically, you could do a horizontal mortise and use a pair of "folding wedges". These are simply a pair of wedges coming from opposite sides so that the mortise doesn't need to be tapered. The downside is that you don't get any help from gravity holding the wedge in place, so you may have to tighten them up more frequently.

[Alan DuBoff]

I'm a fan of draw bored as it holds the joint together on something like a workbench base. However, if one was thinking about having a bench that could be knocked down, a tusk tenon or similar could work for that.

Is it this type of tenon:

http://sawdustmaking.com/woodjoints/images/f153.jpg

If so, that would probably work fine.

Bob Lang used some wedges on large dovetails he designed into his knockdown bench recently, featured on the cover of Popular Woodworking.

http://blogs.popularwoodworking.com/editorsblog/content/binary/0630BLOG_1839.jpg

Since I don't have Andy Rae's book, I am not exactly sure what you describe.

[Pam Niedermayer]

Lucas, your example is a fox wedge tenon, typically used in furniture, a bit tricky to get it right, probably not all that good for a bench.

Michael, a wedge, as in cutaway the side(s) of a tenon and insert wedge on assembly, should work fine. A secondary advantage is that your bench will be knock down.

Pam

[Lucas Bittick]

I'm confused-- so does the "wedge" in wedge tenon refer to the mechanics or the shape? From Michael's pic, it looked to me like a tenon was capped with a mortised block. The fox wedge was the only thing I could relate to that would hold it together.

So how does this all work? A removable wedge allows the disengagement of the tenon?

[Pam Niedermayer]

I'm confused-- so does the "wedge" in wedge tenon refer to the mechanics or the shape? From Michael's pic, it looked to me like a tenon was capped with a mortised block. The fox wedge was the only thing I could relate to that would hold it together.

So how does this all work? A removable wedge allows the disengagement of the tenon?

"Wedge" is a generalized description, of which there are several varieties, and generally refers to the mechanics which drive the shape. I can't see any wedges in Michael's bench at this point; although there appears to be a cut out above the tenons for wedges, one each leg.

Since Michael's will be through tenons, there's no place for a fox wedge, which needs a blind mortise to work. However, a fox wedge is defined by the blind mortise; and probably in Michael's bench your wedges would be just wedges, would work fine. My bad, I was thinking about a wedge on the top of the tenon because of Michael's slot.

Yes, a removable wedge allows you to knock out a tenon for disassembly.

Pam

[Frank Drew]

As Pam notes, the fox wedged tenon is a tricky joint and once it's together you can't take it apart; that's also what makes it so chancy to make... you really only get one shot and that's at final assembly since the very thing that makes it strong makes it impossible to take apart once the wedges hit the bottom of the mortise and start spreading the tenon. If you've mismeasured something you're likely SOL.

[Michael Hammers]

Hi everyone,
Yes, without pictures it is rather hard to envision the joint in question.....
Suffice to say that instead of boring through the center of the protruding "tenon"...you make a 2 degree angle wedge and cut on the OUTSIDE of the tenon. So you have one cut on each side of the cheek where the wedge slides over the rail and the wedge acts like any other wedge.
My main concern is that of lateral movement. So looking at this pic the waste is removed on each side of the cheek verses the center as a traditional tusk. I think it would draw the leg up nice and tight, I just was more fearful of it not having material on each side of the wedge, effectively leaving it exposed.
Make sense?

[Marcus Ward]

What exactly are you going to do on this bench? Land aircraft on it? The wood you're making it out of isn't exactly kindling. Unless you're planning to push it off a moving truck, boring through the tenon and pegging it will work just fine. I've tested these joints, the mortise fails first. Trust me. Trust the thousands of craftsmen who came before you. :)

[Robert Rozaieski]

Make the through wedge for the tusk tenon go through the tenon horizontally rather than vertically and there will be no chance of blowing out the sides of the rails.