At what angle should a grafting knife be sharpen… and what kind of stone should be used?
You want to have the knife at a fairly shallow angle (i.e. the knife is almost laying flat – but not quite). If you use a greater angle, it just means you’ll need to sharpen more often (something I do anyways).
I use a green oilstone. Don’t know the brand or type, as I bought it used at an antique mall (came with a wooden holding case).
I also use a diamond sharpening tool for field sharpening (like a chef’s sharpener, but much smaller).
Hope this helps.