This is where I got to today. Four braces with tenons done and 3/4 of the mortices marked out. I ran out of light.
I had the benefit of Ben’s presence this morning and he showed me how to do the nose on the lower tenons which I struggled with yesterday. This is how it’s done.
Marking up the tenons
Start by marking the position of the brace on the side of the post and the underside of the wall plate.
These are the positions we are working to.
Transfer this line to the brace using a plumb line to give you a mark for the bottom of what will become the tenon shoulder.
Move the plumb line to the other side of the brace to get a mark for the top of the shoulder. Then before removing the brace make a rough, hand-drawn mark on the underside of the brace roughly parallel to the side of the post. This will be handy when you flip the brace over and are trying to locate the shoulder marks.
With the brace flipped over, use you hand-drawn line to help you locate your precise shoulder marks and mark the shoulder with a straight edge.
Now you can mark the tenon and what you do next depends on whether you want a nose on the tenon like this…
…or not. We have decided not to have nosed tenons at the top of the braces. So, for the top tenons we proceed as follows. We mark the outside side of the tenon at a right angle back from the shoulder line from the point where the shoulder line hits the under side of the wall plate.
To make a nosed tenon we move the square back an appropriate distance along the shoulder.
To get the size of nose we want, we found that we need to move 16mm back.
With the lower edge of the tenon marked. You just need to mark the tenon depth. We’ve gone for 80mm tenons.
You can now cut the basic shape of your brace. This what the markings look like for a nosed tenon.
Once cut, you can mark out the tenon itself on the brace “blank”. In our case all the braces on the front and rear walls have just one shoulder.
Marking up the mortices
Once the tenons are in place you can mark out the mortices. I used plumb line or spirit level to do this. The outside edges of the mortices line up directly with the edge of the tenon shoulder (with or without nose). However, the inside edges of the mortices need to be slightly elongated. I’m not quire sure why this is but it’s definitely a feature of the oak frame of our extension. To get a consistent elongation, I used couple of spacers.
Then I used a plumb line from this mark to define the inside edges of the mortices.
With the ends of the mortices marked, I used a spirit level to mark the mortice sides.
Onwards and upwards.