Hi coolford,
Thanks for adding a couple great posts to the thread! When I get an old plane with an iron that’s dull, nicked, pitted, etc, I generally try to determine the angle and then grind a new one. On a typical bench plane, that’s usually somewhere around twenty five or thirty degrees. I really like your low tech, but effective, method of re-grinding the cutting angle. And like you mentioned, as long as one doesn’t overheat the steel, your method for re-grinding is sound and efficient. It’s a good idea!
Many years ago, when I started to figure out that planes were GREAT tools to have and use, it became apparent pretty quickly that they weren’t so great if they were not tuned and their cutting irons weren’t super sharp. A really sharp iron is half the battle, and they make the plane a lot safer to use. Anyway, I bought a book and a few other things (like stones for instance), and did some investigation into sharpening my plane irons, as well as chisels, and other tools. I did it all by hand and got pretty good at it, but as you likely know, sharpening can be a slow process. I’ll freely admit that it’s not my favorite activity out in the shop, but certainly a necessary one. So, after years of sharpening by hand, I bought a slow speed grinder that bathes its wheel in a water trough as it spins. The slow speed and water essentially eliminate the possibility of overheating a cutting edge, which I did more than once on my regular grinder. The slow speed grinder was equipped with a few jigs that allow the user to achieve almost any angle uniformly across a cutting edge. It speeds up the process tremendously and the accuracy is right on the money! Once I have the desired angle, I polish it to a mirror-like finish on sandpaper glued to a flat granite slab, or a section of float glass. I adhere the sandpaper to those flat surfaces with spray adhesive. I usually start at 400 grit and end somewhere around 2000 grit. I do it by “feel” and totally free hand. Once I’ve got the cutting edge polished, I mount the iron back on my slow speed grinder and run the edge over a leather strop wheel loaded with a fine grit paste polishing compound. When I’m done, the finish on the cutting edge is literally a mirror, and SUPER SHARP!
Jim C.