Exactly how flat does a sharpening stone need to be? Exactly how flat, for that matter, does a plane need to be?
I’m on holiday. Here is a toy plane, a soft building block, and a half brick (not cut by me):
The plane started out rather rusty, as did the iron (why do I always forget to take ‘before’ photos?). The plane sole, lubricated with water, was used to flatten off the soft building block, and it was then used to take the rust off the iron. The half-brick did a much better job of sharpening, but it wasn’t perfect. Then I found a better stone:
Same drill—flatten with the plane sole, then sharpen. It wasn’t the best edge I’ve ever made, but it was pretty sharp. The plane is rather all over the place, but it made rounding off the table edges easy:
