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!

 

[toolsntat]

Too late to expand on this tonight, but shrinkage is worth considering and why you don't glue the outer part of a wedge.

cheers, Andy

 

[Trevanion]

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.

You smack a wedge in between the tenon and the mortice, the wedge compresses against the end grain of the stile as well as pushing end grain into the mortice much like a cut nail.

If you pull a wedge out of traditional work you will see that it is significantly deformed from being compressed against the end grain. It’s that friction that holds the wedge in place, glue or not.

 

[Windows]

More questions:
Q8. Are you also pegging your wedged M&Ts?
Q9. What sequence do you wedge, peg, glue?
Q10. Please tell me all about which parts are being glued?

 

[Mike G]

More questions:
Q8. Are you also pegging your wedged M&Ts?
Q9. What sequence do you wedge, peg, glue?
Q10. Please tell me all about which parts are being glued?

Rarely, but yes, it does happen. And here's the glue, too:





The glue on the tenons is only on the inside, allowing the outside to expand and contract with humidity changes (as a matter of interest, it hasn't moved at all). The wedges are fully glued. Pegs are dry (indeed, they're waxed). I'm pretty sure I would have pegged it first, with the draw-bore action pulling the joint up tight before I whacked the wedges in.

 

[AndyT]

Here's a sample of the sort of thing I have been reading. The Woodworker, Issue No 3, December 1901.






Don't worry if you missed the first few issues, just get the book version of the series:

 

[Richard]

Regarding wedges. I suspect the method I use most often is because I'm a furniture maker. I widen the mortice leaving the inner few millimetres square. The reason for this is that the inner mortice length matches the tenon width, thus the tenoned part can't be caused to to drift left or right as wedges are driven in. Going back to that furniture maker comment of mine, I saw cut the tenon and bore a hole at the end of the saw cut to prevent long running splitting. Typically, but not always, a furniture maker's tenon wedging is both aesthetic and strength giving, see below.

Joiners, in my experience having also worked in joinery workshops, are frequently even more driven by a need for speed than us prissy craft furniture makers. So, take a typical architectural door with six through wedged M&Ts into the stiles, some of which are forked M&Ts, i.e., the mid and bottom rail. Allow, let's say ≤60 seconds per saw cut plus a hole bore and all of a sudden that's perhaps 12 or more minutes taken up with just that task, all depending on how many saw cuts you decide to make. Note; there could be up to twenty saw cuts if the joiner follows the pattern for the forked tenons as shown at the end. So, much easier and quicker just to whack the wedges in at the outer ends of each tenon into the angled mortice, job done ... next. Slainte.

​

 

[Windows]

I’m finding this thread very interesting & useful. Thanks to all who have responded so far.

 

[Cabinetman]

Thanks for the pics from the Woodworker Andy, very informative as always, the only books of mine that weren’t dumped when they all become mouldy- far too valuable!
Took me a minute to see any benefit in fig20 V, widen the mortice and then fill it in? But of course when the side grain of the tenon is glued to the sides of the wedge it forms an immovable shape, so much better than a straight tenon just glued in, and of course also better than gluing to the end grain inside the Mortice.
Another benefit of this over traditional fox wedging is that if you get it wrong it could be removed whilst the glue is still wet which isn’t at all the case with the other method (at W).

 

[Woodbloke]

Wot @Richard above does, except that more often than not the tenons aren't flushed off (boring) but left proud by around 3mm and then rounded over with chisels and sanding blocks. Tricky but looks better - Rob

 

[chataigner]

Can I pop in a supplementary question pls ?

For exterior joinery, windows for example, do you prefer through tenons which expose end grain to the weather but simplify wedging, or fox wedging, trickier to do and probably less strong ?

 

[Trevanion]

Can I pop in a supplementary question pls ?

For exterior joinery, windows for example, do you prefer through tenons which expose end grain to the weather but simplify wedging, or fox wedging, trickier to do and probably less strong ?

I've always done through mortices with wedges, but I know a lot of people do blind mortices with no wedges at all, just glue and some nails fired through the face. I suppose with modern glues, traditional jointing methods aren't quite as relevant, but I still think it's good practice should the glue ever fail.

I've personally never seen old joinery fail from the end grain of the tenons back into the stile, it typically fails at the top edge corners of the middle and bottom rails, where the mortices goes into the stiles. Most of the time, where you see end grain failures is where it's been left in contact with the ground, like a door that's been left to sit on the floor because the hinges have caused it to drop down.

 

[NickM]

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.

Sorry, late reply to this:

1. I try to go as close to all the way as possible but leave 1 or 2 mm square.

2. I've done both but was taught at Edward Barnsley to angle the cuts. I go to about 1 or 2mm from the edge of the tenon.

3. If the kerf in the tenon is angled as in 2 above, you don't need a hole. Before I angled the kerf in the tenon, I did drill holes.

4. The hole makes it easier for the wedge to go in.

5. I haven't thought about this. You need to leave enough "meat" outside the mortise so that the wedge diners blow out the end.

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. Square first and flair it later.

7. Mark the flair and then chisel it by eye. I usually chisel from both ends of the mortise.

 

[Windows]

It seems to me that through tenons exposing a small amount of end grain to the side of a window are small beer compared to the area of end grain at the ends of the stiles at top and bottom of the window. But none of these areas seem to suffer the worst of it because windows are actually quite well protected at top and sides by eaves and frames and various overhangs (at least on older houses), and of course by paint, oil, etc so they last quite well.

Personal experience suggests that the worst hit parts of a window are in the bottom third on the exterior face where a horizontal part joins a vertical or behind cracked putty. The rain protection from the rest of the house is reduced lower on the window, putty drying or differential movement of the wood causes paint to crack at the joint, and the horizontal doesn’t shed the water while the remaining paint film prevents the wood from drying. These are the failures I’ve seen anyway.

Worth noting that the design of the wedged M&T means that the exterior bottom edge of the mortice slopes down so if a failure occurs in that area, the chance of water sitting there is reduced.

But I think the considerations for a window must be pretty different than those for a gate that could be completely exposed to weather on all sides and sits lower to the actual ground.

 

[Windows]

So say you’re at the stage where you’ve cut the straight mortice and tenon and you’re doing a dry fit, how do you decide whether a problem is going to be fixed by adjusting the M&T versus some other fix? What level of perfection do you expect at each stage?

For example, suppose at the dry fit for a window, stiles and rails are at 90° to each other, but there’s a perceptible <1mm level change on the face of the window where stile and rail meet. Are you not bothered because it’s a common problem and you always plane after window is complete or is this a rare issue that needs addressing straight away and must be caused only by an ill-fitting M&T?

Basically, what kind of checks do you make and what troubleshooting steps do you follow at the dry fit stage and each stage of assembly?

 

[Mike G]

1mm is quite a lot. Is it the same on the other side? If it is, then it means that one piece is twisted in relation to the other. If you introduce a twist in a joint, you risk introducing a twist into the window (sash, casement, or frame). If the other side of the joint is flush, then you have a stock preparation issue, and that could lead to a twisted or mis-sized final piece.

 

[Windows]

Yeah 1 mm is a lot. Let’s say it’s 0.4 mm or 0.3 mm. Sounds like you have low tolerance for defects at this stage. You’d check the stock and the mortice/tenon then and eliminate the issue before going further?

 

[Mike G]

Well, 0.3mm is a different thing. So long as nothing is in twist, then I'd carry on. The thing is, I tend to make all the components at the same time, so I wouldn't see an issue like this until the final dry assembly. If everything sat flat and true, I'd just plane it away. If, however, there's a twist, I'd be remaking the part/s in question.