Wednesday, 3 May 2017

Making 30 M&T Joints

Spring isn't getting warmer.

That will give me some more time to complete the bench.

A lot of mortise and tenon work has to be done.

The last week I had a few days off. I thought I could spent my days in the shop. As always, it came differently than one thinks. Nevertheless I made progress.
The main parts of the frame together it now came to the point of caring about the back slats. I decided to go with 15 slats. Don't ask me how exactly I came to this number. One criteria was amount of material. As I were cutting it I found out that I had some pieces which weren't usable. Some started to split, some other had resin encapsulations. 
That in mind I found a good spacing. The slats are 30 mm wide and the distance between two slats is 40 mm now. I think, so it isn't looking too uniform.
Having 15 back slats does mean 30 mortises and tenons had to been made.
To layout the mortises I have clamped the back and the crest rail together and then marked the spacing first.

Layout out of the spacing

Next I have set a marking gauge and laid out all the mortises. If you are asking yourself what the heck are the middle lines good for, then the answer is pretty easy. I have marked the middle of the joint, so that I have a reference point for drilling out the waste. I'm not very good at eyeballing. So I grabbed this little help.

Mortises laid out

Next was drilling. Setting the drill bit onto the middle line and start boring. As easy as that.

Drilling out the bulk of the waste

Drilling out the bulk of the waste is a good method as I find. For me it is quicker than chopping only.
It is quieter than chopping. And finally the last step to clean the mortises or more paring than chopping action.

Chiseling out the waste

After I had drilled out the waste I have defined the walls of the mortises. As mentioned by mostly paring.
The only action were I have used a hammer was for the ends of the hole. 
Done that 15 times, the back rail was done. 

Back rail done

Now the crest rail could be done with the same procedure.
I had made a test slat so that I could verify every mortise. It was slightly undersized so that it would fit in every case.

Test fit of the first slat

Impatient as I am, I had to have a sneak peek. A few holes to go and then 15 slats with 30 tenons will have to be made.
I already have roughly prepared all the needed slats.

All slats roughly cut

So far, so good. It takes time.

Finally I have got a question for you about draw boring. I plan to draw bore the longer rail joints, because I haven't got clamps which are long enough. Maybe the question is stupid, but has the hole for the pin in every case going through the complete material. Or can be done, let's say concealed (don't know if that is the right term)? Every opinion is welcome.

Take care!



  1. Stefan,

    I work both ways, peg all the way through the mortise piece and 'stop' peg. If you are doing a 'stop' peg you have to be careful to make the peg shorter than the depth of the bore hole. If you do not and are not careful you can punch out the back side.

    Either way works.

    That is a ton of mortises, while I enjoy the process I might have to split that job up.


    1. Hi Ken,
      thanks for the input. That make sense for me.
      Yeah, I had split up this job too and done a little side project.


  2. Something to consider if you used stopped draw-bore pegs - you need to taper the end of the peg so it will get into the further hole. But with a stopped hole, you need to have enough depth so that the tapered part of the peg goes completely past the further hole and the non-tapered part of the peg can do its job inside the further hole. So the amount of thickness in the mortise "cheek" is important. Always best to try a test joint first.

    Not sure if I said that properly, but hopefully you get the idea.

    1. Hi Matt,
      thanks for your input. Yes, I think I got your point.
      So, I have to make pretty short tapers at the pegs. And deep enough stopped holes.


  3. For your first attempt I will go with thru holes for drawboring. That way you will gain the most strength and no worries about blowing the back or erring on the cautious side hand not engaging deep enough both sides of the mortise.
    My two canadian cents (No idea how much that is in Euro :-)

    Bob, as told by Rudy

    1. Hi Bob,
      that's about one cent in Euro ;-)
      But every valuable hint is priceless. So thanks for your advise.
      I have already got some experiences with full thru draw boring. I was just wondering if they have to be thru in every case.

      All best and give Rudy a treat.