I'm just starting to try to hand cut some dadoes in some old knotty pine, the kind of wood paneling found in many older homes from the 30's, 40's and 50's.
I'm trying to cut cross grain in wood that is 1 & 1/2 inches wide. The dado dimensions are 3/4 inch wide by 1/4 inch deep.
The technique that I'm trying is to first chisel a saw channel on each side of the dado, then to saw down to 1/4 inch depth. My first attempt gave poor results and it was just too easy to cut too far, even though I was stopping very frequently to check my sawing progress.
So, I stopped using the 12 tpi back saw, and tried a hacksaw. This gave better results:
1. the kerf is very clean and narrow
2. the cut is not aggressive, which allowed good precision in sawing down to the 1/4 inch depth - this was a great help!
3. the "open" nature of the hacksaw allows you to see both side of the cut at the same time
I'm just beginning and I'm sure that there may be drawbacks to this method, but so far it is working better than the back saw.