Great idea about the pig sticker! I find that it’s easiest to just use a 25 degree bevel. It makes resharpening much easier. I use a belt sander to establish the bevel. Just be very careful. I drew the correct angle on the sides of the chisel (with a protractor), and put the bevel to the belt sander until I reached that angle. Be mindful to make sure there is absolutely no wood saw dust in your belt sander, and don’t use a shop vac. Because the metal sparks can cause a fire. And there’s not much need to hone a mortise chisel to a fine grit. This is a wedging tool, rather than a paring tool.