eliotandmax
I read your post a couple of times and noticed that you excepted HSS. What't the problem with it? The plane iron I just sharpened is something with a rather high hardness( I think Rockwell 82 -or was it 62?) And it was cryo -hardened. I did have a hard time sharpening it on my stones. I even started at 250 and couldn't get anywhere. Tried a Tormec , which also took forever. Finally took it over to the wheel I use for turning tools.That took a few seconds! Then finished with all the Nortons I have, up to the 8000. I happen to have some old honing blocks that I picked up at an antique shop years ago -- I think for razors -- and finished up with those. I believe it's really sharp. The only way I have to test is the old thing about shaving hairs off my arm; is there a better test? Oh, I forgot. I also have two so-called 'Spider' ceramic sharpening "stones"( One is labeled 'fine' and the other 'super fine'). I always end with these. I believe these give the best edge but don't know that much.