I hate to open up this can of worms but I’ve run across a situation where I like having either the original plane iron or a thicker Hock iron in my scrub plane. After watching Paul’s method of converting a #4 into a scrub plane I followed his directions and put a 10″ radius on a Hock replacement iron. I had to fettle the mouth of the plane slightly but it ended up working fine. Then I ground a smaller radius, 8-9″, on the original iron, which is about a mil thinner that the Hock iron. When I switched back to the original iron, the mouth was naturally set quite a bit more open merely due to the difference in thickness of the iron and the scrub plane became an even coarser scrub plane. And it didn’t require loosening and adjusting the frog! I don’t have access to a thickness planer, so unless the lumberyard dimensions all my wood for me, I do my stock prep by hand and it’s nice having the fine vs. coarse scrub plane.