Wedged M&Ts

[Windows]

A quick survey about your use of wedged through M&Ts please:

1. Do you angle the mortice all the way to both edges or do you stop short leaving a 90° part to the mortise?
2. Do you cut the kerfs in the tenon roughly parallel to the sides of the tenon or do you angle the cuts?
3. Do you drill holes in the tenon at the bottom of the saw cuts?
4. If you drill holes, why are you doing it?
5. Do you consider there to be a relationship between the shoulders on the tenon and the wedges?

Thanks for taking part if you decide to do so.

 

[Mike G]

1. I leave a short square part.
2. I've done both. I haven't made my mind up yet which I prefer. Bear in mind that many, if not most, wedged tenons are done without a kerf at all, with the wedge being inserted between the tenon and the sloped sides of the mortice.
3. Yes
4. To stop a crack caused by the wedge from penetrating out into the rail
5. I don't understand the question. The wedges are pulling the shoulders up tight against the stile, and forming a dovetail to keep them there.

 

[Dr.Al]

2. I think I've done it straight on the ones I've done, but haven't really spent any time thinking about it.

For all the others my answers are the same as Mike's.

 

[Windows]

Thanks Mike. I made Q5 a bit vague, didn’t I? What I really mean is do you define the size of the wedges/mortice in relation to the size of the shoulders on the tenon or vice versa?

I have seen someone create the wedges from the pieces cut off the tenon to create the shoulders. I also wondered if people might size the wedges to match the tenon shoulders for aesthetic reasons even when using different material.

 

[Mike G]

Using waste material from the tenon to make the wedges is sensible, because it is already the right width (thickness). Other than that, I just pick a random angle on my gauge, trying to balance the odds of breaking the tenon (outside the kerf) with the maximum steepness I can get for strength. There is no formula.

 

[toolsntat]

A quick survey about your use of wedged through M&Ts please:

1. Do you angle the mortice all the way to both edges or do you stop short leaving a 90° part to the mortise?
2. Do you cut the kerfs in the tenon roughly parallel to the sides of the tenon or do you angle the cuts?
3. Do you drill holes in the tenon at the bottom of the saw cuts?
4. If you drill holes, why are you doing it?
5. Do you consider there to be a relationship between the shoulders on the tenon and the wedges?

Thanks for taking part if you decide to do so.

In joinery not furniture making....
1, Stepped 90
2, never done it
3, never done it
4, never done it
5, yes, always use tenon haunch material as wedges

Cheers, Andy

 

[Windows]

6. Do you cut the mortice entirely square through before cutting the angle or do you do it as one operation?
7. How do you cut the angled part so as to leave part of the mortice square? Are you using a guide for your chisel? Or eyeballing?

 

[Dr.Al]

6. Do you cut the mortice entirely square through before cutting the angle or do you do it as one operation?
7. How do you cut the angled part so as to leave part of the mortice square? Are you using a guide for your chisel? Or eyeballing?

6. Yes
7. Eyeballing

 

[Steve Maskery]

For something like a window, I would cut my mortices on my hollow-chisel mortice and use a wedge underneath the workpiece to cut the angled ends of the mortices. In that way I can cut all my wedges with a single setup.
S

 

[toolsntat]

6. Do you cut the mortice entirely square through before cutting the angle or do you do it as one operation?
7. How do you cut the angled part so as to leave part of the mortice square? Are you using a guide for your chisel? Or eyeballing?

6. no angles
7. machine from shoulder side to appx over midway and do the same from wedge side but moving chisel over lines giving space/step for a gap.

 

[Trevanion]

Because I do all my mortices with a hollow chisel morticer, I found the fastest way to produce the wedge space is to put roughly half the chisel over the edge of the mortice, plunge into the stile and crank the handle so that the chisel is travelling into the mortice at an angle as you pull down. Obviously, you need quite a stout machine to do this operation and I don’t think you’ll manage it with a bench-top model. Some people claim that it does shorten the life of the chisel but I’ve had very few chisel breakages, these mostly happen when the auger snaps and wrecks the chisel box.

For wedges I do reuse the material that comes off the haunches as others have already mentioned. It used to be done with a coping saw to cut out the bits in between the tenons but these days I use an oscillating multitool. There used to be special haunching/relishing machines that would actually cut the haunch and make wedges out of the pieces using a series of circular saw blades, but I have only ever seen these in very old catalogues.

As for kerfing the tenon for the wedges to go into, I personally do not do this and I don’t think it’s best practice either. I always wedge between the end grain of the stile and the long grain of the tenon, the compression against the end grain locks the wedge in place. Wedging into the tenon can cause the rails to split, which I have seen happen with heavy-handed joiners who do this practice, especially with bare-faced rails for overboarding. You will see the method I use often on traditional joinery, whereas wedging into the tenon itself seems quite a new technique as you only really see it on modern work.

 

[GaryR]

I'm going to disagree (mildly). If you place the wedge outside the tenon, then mechanically you have nothing more than a finger joint that relies on glue to hold the joint in tension, and it is no stronger than a straight unwedged tenon. If you wedge inside the tenon, when under tension the tenon has to compress. It resists compression and that wedging action is what holds the joint rather than glue.

The counter argument is that if you glue the wedge onto the tenon from the outside, and glue is stronger than wood, you are effectively making a dovetail which should be as strong as an unglued dovetail.

 

[Mike G]

.......The counter argument is that if you glue the wedge onto the tenon from the outside, and glue is stronger than wood, you are effectively making a dovetail which should be as strong as an unglued dovetail.

Well, exactly. I'm not sure why you would argue as per your first paragraph when you then counter it with the obvious in your second.

 

[GaryR]

A subtle distinction comes from how you glue the wedge. If you attach the wedge to the outside of the tenon, then it should be glued only on the tenon interface. If you glue the wedge onto the mortice face as well, then you eliminate the wedging action and the tenon is held only by resistance to shear rather than wedging.

If you insert the wedge into the tenon, then you can glue one or both faces, or neither, and still get the wedging action.

 

[AndyT]

I've not looked at your spreadsheet yet but it's interesting how the discussion is going.

A common use case for wedged through tenons is in making room doors and some answers are about that. I expect that one extra reason for preferring wedges outside the tenons in door making is that you can selectively adjust the wedges to make sure that the door is properly square, even if you don't have long cramps available.

If you are making a door, you will inevitably have some haunched joints, so the wedges would naturally be cut from the haunch material - it's obviously efficient.

You want the wedges to finish beyond the stiles, so they can be trimmed off neatly once the glue is dry, therefore you don't splay the mortises to the full depth. (If you did, you'd make extra work cutting longer wedges separately.)

Some of my old books show the stiles marked all round for the mortises but with extra marks for the splay just on the face side and edge. I expect this was helpful for a beginner following the book, to make sure they'd cut everything right, before starting to glue up, but would soon become unnecessary as experience was gained.

But room door construction is not the same as fine cabinetmaking, where different timbers and dimensions scale would apply.

I expect the same goes for the measurements, you'd get a feel for what looked right.

So often, you can just look at an existing example of what you need to make, and copy that.

Except if you are an amateur, wanting to try a bit of everything. Then, some suggested sizes will be helpful!