Timber Framers Guild Forums General General Forum Questions Cutting a tapered mortise

I was feeling motivated, so I drew it up. Here's an 8x8, that is way of out square (it measure 9.5" on on corner) to exaggerate things. The tenon slopes 1.5" over 8", the wedge slopes 3/4" of 8", and it is haunched to 7".

[IMG]http://i167.photobucket.com/albums/u122/timberwrestler/Halfwedgeddovetail1.jpg[/IMG]

This shot describes things a little bit. The haunch would be cut out after the mortise is complete.

[IMG]http://i167.photobucket.com/albums/u122/timberwrestler/Halfwedgeddovetail2.jpg[/IMG]

And here's a shot straight on at the inside of the post showing those 3 angled surfaces:

[IMG]http://i167.photobucket.com/albums/u122/timberwrestler/Halfwedgeddovetail3.jpg[/IMG]

It's weird, but it works. Maybe I should make a video...

As a blanket statement, all of my out of square timber are diamond shaped, they don't change in size. I use a slightly different approach. The two opposite sides are parallel and I only drop down the next best face, for the most part, and connect lines on the opposite side of the next best face. This could change if I choose to make the side of the timber the best face, which I don't usually do.

Hello everyone tonight

Great topic

I have been following the conversation with interest because I had the opportunity of examining an early truss in a 1865 lutheran church's attic

This truss's bottom chord was 12" square hand hewn, and the bridge truss that supported half the weight of the spire had legs that were fastened to the chord with half dovetails held in place with wedges driven from the top

with shrinkage over the years the dovetails have moved upwards about .5" out of their seatings but still holding tight--great joint

NH