Replies

1. 
   lat_axe | Mar 20, 2024 05:41am | #1

   A lot of my furniture uses wedged M&Ts. There's two approaches:

   1) The wedged tenon is used without glue, as it provides a mechanical grab, with the wedged splay of the tenon preventing the tenon pulling out of the mortise once its inserted and then wedged. The advantage is that it's easier to disassemble if necessary, especially if you leave the wedging shards proud, so easy to pull out of the tenon ends. You can also shape the ends and wedging shards to be decorative, with contrasting wood for the shards. You can also leave them proud, as a "feature".

   2) The tenon is wedged but also glued (both into the mortise and the wedging shards into the tenon ends ). This makes a "belt & braces" very strong joint, with both mechanical grab and glue grab between the parts.

   With the no-glue variety, you have to be careful how you cut the gaps in the tenon ends into which the wedging shards will be knocked. The cuts for the shards should run parallel with the grain of the tenon, if possible, so that the tenon grain structure doesn't crumble when forced apart by the wedge shards being knocked in.

   With the glued joint the grain direction is less critical as the wedged tenon, when glued, becomes one strong piece.

   In both cases, the mortise needs to be flared so that the wedged tenon will completely fill it, with sufficient flare to provide that mechanical grab (a sort of internal dovetail in a dovetail socket. Especially with softer timbers that compress easily, insufficient flare of the mortise and wedged tenon might allow the tenon to pull out if there's a sufficient force on the tenonned member to compress the flare so that the wedging ceases to work as a retainer. This is most likely with the unglued variety.

   The usual convention is to make two cuts for two wedges in the tenon ends, not one. This gives more scope for flaring without a grain crumble or snap in the tenon. Cutting the slots for the wedged shards near to the tenon ends also tends to make it easier to flare the tenon.

   You can cut the tenon-ends with the wedge shards in it flush with the apron its inserted through. You can, in some designs, leave the tenon ends and wedge shards proud, making them very neat to become a decorative "honest" joint. (Boasting the joinery to any observers of the piece). But perhaps not in that design of yours, which is quite delicate looking and minimalist.

   Your design, by the way, could achieve the same glue + mechanical grab of the upper cross members if you used a dovetail joint, with the tails on the cross member ends and the sockets cut into the top of the tables aprons. For extra security, you could also screw or dowel the tails into the aprons. That joint might weaken the rather minimal aprons, though - but perhaps not if very well-made and glued.

   Lataxe

2. 
   starideda | Mar 20, 2024 06:04am | #2

   Thank you.
   As a beginner the mortice and tenon join with wedge in it seems the most easiest solution to make plus it is a strong joint.
   I mostly saw wedged mortices that use two wedges, but did not know where is the advantage so I though one would work. But it makes sense that putting wedge closer to the edge of a tenon makes it easier to put wedges in it.
   I did not however completely understood the part on flared mortice. Does it have to a little bit "more open" on the side where is receives the wedges so the tenon could "spread out" a bit? Or should the tenon be a little narrowed so it expands once it receives wedges? I guess the mortice has to have constant width so it could receive the tenon in the first place, right?
   I do have hand tools only and I plan to make slots for the wedges using Ryoba japanese saw. But I guess this does not matter much.

3. 
   rob_ss | Mar 20, 2024 06:10am | #3

   Lataxe is right of course, but I'm going to disagree a little anyway!

   You don't need wedges.

   Glue is strong enough if the joint is well-made.

   I don't do much through-tenon work and have used wedges occasionally, but they are really only there for decoration. The exception is if the joinery is not perfect - a wedge can be a handy 'design opportunity' to fix that.

   There is overmuch concern over what makes the strongest possible joint, but in most tests I see, the forces required to break the weakest joints are far in excess of those which are seen in any well-designed furniture, chairs possibly excepted.

   Thing is, if you design your piece properly, it should minimise the forces on the joints, and should account for the forces where they are unavoidable. The joints where you plan the wedges really should not experience any significant forces - the legs will fail long before that happens.

   Even so, I'd totally put a bit of maple in there, just for the look of it.

4. 
   starideda | Mar 20, 2024 07:00am | #4

   I understand that wedges mortice and tenon could be an overkill for such construction but there are things here:

   1. I am a beginner woodworking working with hand tools only, so the joints might not be completely precise and crisp.
   2. The table will be used in a bathroom where moisture is expected. Although it will be glued with waterproof glue and covered in linseed oil several times, I expect that the wood will continue to work and could weaken my (unprecise) joints.

5. 
   gulfstar | Mar 20, 2024 07:19am | #5

   Wedges are good but dont overdo it, I see in your sketch à beefy tenon with a wedge in the center, that makes a lot of stiff wood to push sideways. I prefer two thin wedges 1/4 inches from the edges so the wood can bend without breaking at the base of the tenon.

6. 
   _mj_ | Mar 20, 2024 07:39am | #6

   If you are not confident in cutting perfect joints maybe it's better not to dive in with through tenons. A stopped tenon with a drawbored pin will do what you need and not show wide glue lines on the outside surface. It is still functional and a bit fancy if you choose a contrasting wood for your pin.

1. 
   john_c2 | Mar 21, 2024 02:46am | #10

   This.

2. 
   russ_rva | Mar 21, 2024 09:22am | #11

   I am a hobbyist woodworker and have been thinking about using through tenons on a coffee table design.

   Since I will be looking a this table in front of my chair and will be seeing the through tenon mortises every day, I am attracted to the idea of stopped tenons. I like the idea of using a contrasting wood pin, but I’m not clear how a draw bored pin works in a stopped tenon.

   I may be the only reader who doesn’t know this.

1. 
   _mj_ | Mar 21, 2024 09:56am | #12

   Enter " drawbored " into the search box at the top of the page, you'll find lots to read.

1. 
   Deleted | Mar 21, 2024 10:14am | #13

   “[Deleted]”

2. 
   russ_rva | Mar 21, 2024 11:20am | #14

   Thanks for a prompt reply.

   I should have include a picture of the table I am thinking about. Photo attached.

   I have been inspired by this Nakashima table. Rather than make my best effort at a copy, I wanted to think about using through tenons for the spindles and/or the attachment of the legs to the table top.

   That's a lot of opportunities for a hobbyist like me to create some mortises that are less than perfect and a constant reminder that Nakashima pieces are masterpieces for a reason.

   I thought that a draw bored pin for the tenons would make an interesting modification. But I don't that this particular design would accommodate that.

   Thanks again for helping me think about this.

   
1. 
   _mj_ | Mar 21, 2024 11:29am | #15

   Yeah, this looks nothing like the sketch that started the conversation.

2. 
   russ_rva | Mar 21, 2024 12:03pm | #16

   A missed communication on my part. I interrupted the original thread with an entirely different design question. Sorry.

7. 
   lat_axe | Mar 20, 2024 08:37am | #7

   There's a quite a bit on wedged tenons within the Fine Woodworking archive. Here's the link to a basic article from 1997:

   https://www.finewoodworking.com/project-guides/joinery/designing-the-wedged-mortise-and-tenon

   There are many more articles, often as part of a build, so you can see the various usages of wedged tenons in practice.

   Lataxe

8. 
   starideda | Mar 20, 2024 09:22am | #8

   I was thinking about stopped joints which to be honest look better to me (the side element is without any holes/disruption), but I was concerned about the strength of them. This is why I started thinking about getting full through the side elements and possibly making wedges.
   But if this is not necessary, I would go rather with stopped mortice and tenon joints.

9. 
   rjlii | Mar 20, 2024 09:51am | #9

   I've wedged thru tenons as well as pinned both stopped and thru versions. I like the look.

10. 
    joeleonetti | Mar 21, 2024 03:51pm | #17

    I've used wedge tenons before. I like to use them from time to time. Go ahead and try them. You could always first do it on a practice piece before the real deal. Good problems to have.