Quote Originally Posted by TwistedOak View Post
to add to the comment about SS being hard and therefore requiring more honing time. Isn't carbon steel generally "softer" and easier to put an edge on than Stainless?
If my memory is correct, then that would make using the same honing routine for both steels a recipe for 50% success at best. I would use a minimum circle/stroke benchmark on a bevel setting stone for any type of razor, but only as a reference for when to start checking if the bevel is fully set. Then continue on as each individual razor requires.
The stainless on older razors is probably actually a softer spec, but the carbides that are in it are much harder than any plain carbon and iron mix.

On new razors, I don't think a lot of the carbon razors themselves are really that hard, so it's hard to say.

When you use tools, and you get to high speed steels and other highly alloyed abrasion resistant steels, when they are equal hardness, the carbides make the high speed steels or hard stainless type steels much harder to abrade on a stone.

I would imagine that the friodurs are probably 440C or some reasonable approximation of it, because that would be a good inexpensive stainless that hardens and tempers well in the 58-60 range of hardness. They are cryo treating the razors to disperse the carbides and make them much more uniform and integrated into the steel matrix, so you might never notice that something is even stainless in terms of sharpenability if it's a click or two softer and cryo treated.

Cheap stainless will have large carbides, and non cryo stuff that is loaded with carbides (like D2) will often fail with tiny chips early, and then retain whatever edge is left after that for a very long time.

Anyway, it's my supposition after running into these steels with woodworking that if they were to do anything to make sure that stainless was sharpenable on natural stones, it would be to cryo treat it and then make it a tick or two softer on the C hardness scale so that it retains sharpenability. 62 hardness 440C or steels like D2 are not particularly friendly to natural stones (D2 has a lot of chromium, IIRC).

If you are using synthetics, you can disregard most of this unless the steel you're using (if you get a custom razor) has a bunch of vanadium carbides in it. If it does, even aluminum oxide or alundum type stones (like pretty much all of the synthetics we use are made of) are softer than those carbides.

There's a nice chart at the bottom of this page with knoop hardness of various things.
https://www.tedpella.com/Material-Sc...ng_Systems.htm

Carburized steel is around 800, aluminum oxide is around 2100, chromium carbides (like you'd have in 440C) at 1735. When you get to nutty stuff like vanadium carbides, it's 2660 on that chart (there are a lot of knives made now with vanadium carbides in them in droves, which I have no clue why anyone would want that).

Anyway, when you're using an abrasive like quartz or silicon dioxide or novaculite that's barely harder than carburized steel, then it won't cut chromium carbides. Thus they have to be dispersed or you'll have nodules of unsharpenable material. You can help that along by making the overall steel a little softer after the carbides have been evenly dispersed.