I am not sure if I will have enough single logs long enough to span an entire wall in my sauna. As such, I am prepared to join them together. I've done two such joints already, as practise for the cabin, where I will have to do this multiple times, in multiple locations.
First off, I marked off the two beams in question at three inches in from the end. Then I returned them to the sawmill, where I cut vertical slots into the ends of the beams until my saw had penetrated three inches.
I returned back to the building site, where on one beam, I used the circular saw, set to a 1" depth, to cut off the outside pieces of the end of the beam, 3" in from the end.
The other beam I drilled down between the cuts from above using my 1" spade bit. This freed up the 1" by 3" block of wood in the end of the beam and created a nice slot for the tab I had just created on the other beam.
I prepared them otherwise normally, and placed them on the wall as I would any other beam.
Once in place, I again used my 1" spade bit in the drill to drill a hole from the inside, towards the outside, but checked the depth constantly to ensure that it only just reached the outside, but didn't actually penetrate anywhere.
I centered this hole on the slots and tab I had earlier created.
Into the hole I inserted a dowel, and then using a Japanese style draw saw, cut it off flush with the inside wall.
A single 2.5" screw from above ensured that it wouldn't pull free, and then some caulking to fill in the gap between the end of the tab and the half-rounded slot completed the picture.
We'll see how many more of these I have to do to complete the sauna. But it was again good practise to get it done here before I came to the main cabin, where knowledge of this technique would be a requirement!