I have a new Collins pick mattock, it's great for the typically useless substance Ozarkers are fond of calling dirt. My little piece of it is about 50% rock once it have struggled down thru it to clay.
There's a reason the Army Engineer School is in the Missouri Ozarks, and the Infantry School is in sandy old Georgia. Engineers have heavy equipment and explosives, soldiers only have an entrenching tool, there's only so many hours in the day to teach something.
Thanks for the pic of the belt sander, yes, without the platen, it gets a convex edge nicely. They are rare in tool shops, however, most people seeing a belt sander have an electric powered hand tool in mind. I have a Bosch, runs great, I never sharpen anything on it. Upside down on a bench covered with tool drawer liner, it doesn't move around, but I have never figured out how to get the platen off it. Don't expect to, either.
Suggesting an expensive knifemakers shop grinder for the average guy is a bit pointless when most don't want to pony up the dollars for one. Harbor Freight's are $40 to 70, a Burr King $2,000. A good file is $10 and you can take it with you. Like filing a chain saw, you can stay ahead of it on your break. It's a bit harder to run a belt sander out in a woodlot, and I don't see the cost being a minimum 2X the tool as a positive. If you already have one, use it all you want.
Again, the axe makers need our support. Grind away.