I've settled into liking ~320 or so for Case's blades, precisely due their slightly lower hardness. I sort of found this indirectly, in noticing how one of my cheap Japanese-mystery-steel paring knives responded to the coarser grit, when looking for a decent sharpening solution for that one. That knife simply wouldn't retain any bite at anything much finer. I'd even noticed it was easy to over-strop it on simple green compound (on leather); even that would polish finer teeth out of it quickly. With that knife, I think it's issues were all due to a combination of low hardness and coarse grain; it seemed as if the finer 'teeth' on the edge would just crumble away, like sand, with just a little abrasion. Still tends to do this at coarser grit, but at least the bigger teeth last a bit longer before needing touching up.
Case's SS is better than that one, in terms of holding an edge with some bite. But it's still similar in it's ability to sharpen up easily (that's low abrasion resistance, as opposed to hardness), and in how it cuts at a given grit; that's why I tried the coarser grit on the Tru-Sharp, and discovered I really liked it. Buck's 420HC is a little harder (RC), so it tends to finish up at a somewhat finer scratch pattern for the same grit. To get the same 'tooth' out of it, I'd likely take a step down in grit, to ~220 or so.
Opinel's Sandvik stainless is in another league, so far as I'm concerned. Not so much difference in elemental makeup, but their manufacturing process is famous for it's purity and producing even finer grain. Combine that with higher finishing hardness (they spec 12C27Mod up to RC 59), and it makes for some very fine edges that will hold for a while. I've also noticed, for whatever reason that I haven't yet understood, it always seems to retain some 'teeth', even at higher finish (my Opi is finished to above 2000 grit).
I'm coming to the conclusion that softer and less wear-resistant steels like 420HC and similar kitchen-grade cutlery all respond better to a lower-grit, toothier finish. Attempting to polish them too high, even though great shaving edges are possible this way, always seems to degrade durability of the edge. On the other hand, better quality stainless that's taken a bit higher in hardness will take very coarse or very polished edges equally well, and hold them longer. Opinel's stainless is what convinced me of this, in spades.
David
David,
I'll probably move this set of questions over to the Maintenance forum later this week, but will start the conversation here.
Could you say more about why you're suggested a toothy grit (320) for Case SS as opposed to taking it down to finer grits?
In particular, can you compare what you would suggest in terms of grit for Case SS (420HC at 56Rc), Buck's 420HC (at 58Rc) and Opinel's Inox (Sanvik 12C27 at 58RC)?
I'm choosing these 3 because, as I understand it (and correct me if I'm wrong), at the base level 420HC and Sanvik 12C27 are very similar and have similarly small carbides, allowing for a naturally keener edge (less toothy on account of carbides as with 440C or D2).
Another way to ask the question is, would you also suggest a 320 grit for Opinel Inox and if not, why not?
FWIW, I find my Case to be noticeably harder to hone than my Bucks or Opinels due to the speed it will take a wire edge. It also dulls faster.
