Sharpening S30V blade

[Obsessed with Edges]

The only area where I've noticed the AlumOx not performing well in s30v (or D2 for that matter) was in a stropping compound, and that is still pretty subjective - it did polish up the bevel nicely but there was a difference in quality of the cut compared to the SiC. The Norton India stone is one tough cookie.

There's a similar difference in the cut, when comparing AlOx/SiC to diamond, at grit levels below about ~3µ (i.e. DMT EEF and finer). I've noticed the biggest advantages of diamond in polishing stages at that grit and lower, if taken that far; especially with stropping, using 3/1µ pastes. If finishing to a grit level coarser than 3µ, using SiC or AlOx or diamond, there's not as much of a difference (that I can see) in the character of the sharpened edge. That's all perfectly in-line with the stated average size of the carbides in CPM-S30V, which is 2-4µ. At 3µ and lower, the size of the carbides will become an obstacle, if trying to abrade or shape them individually with softer abrasives.

I've been spending time lately, fine-tuning and polishing the edges on two of my S30V blades (CR Sebenza and a Kershaw Leek), using the 3µ and lower diamond grits (EEF DMT -> 3µ paste -> 1µ paste). With the thinly-profiled Leek's blade in particular, it's cutting as well as my Schrade 8OT in 1095, when polished. I'd previously never seen that in S30V, and had started to assume it wasn't possible. It's come much, much more easily, after I started using the finer diamond grits to get it and keep it there. Was never able to even approach that before, when I was attempting to use finer grits of SiC wet/dry (up to 2000 grit) and/or AlOx stropping compounds. Polished OK, but the edge apex was never nearly as crisp at the highest polish.


David

 

[HeavyHanded]

There's a similar difference in the cut, when comparing between AlOx/SiC to diamond, at grit levels below about ~3µ (i.e. DMT EEF and finer). I've noticed the biggest advantages of diamond in polishing stages at that grit and lower, if taken that far; especially with stropping, using 3/1µ pastes. If finishing to a grit level coarser than 3µ, using SiC or AlOx or diamond, there's not as much of a difference (that I can see) in the character of the sharpened edge. That's all perfectly in-line with the stated average size of the carbides in CPM-S30V, which is 2-4µ. At 3µ and lower, the size of the carbides will become an obstacle, if trying to abrade or shape them individually with softer abrasives.

I've been spending time lately, fine-tuning and polishing the edges on two of my S30V blades (CR Sebenza and a Kershaw Leek), using the 3µ and lower diamond grits (EEF DMT -> 3µ paste -> 1µ paste). With the thinly-profiled Leek's blade in particular, it's cutting as well as my Schrade 8OT in 1095, when polished. I'd previously never seen that in S30V, and had started to assume it wasn't possible. It's come much, much more easily, after I started using the finer diamond grits to get it and keep it there. Was never able to even approach that before, when I was attempting to use finer grits of SiC wet/dry (up to 2000 grit) and/or AlOx stropping compounds. Polished OK, but the edge apex was never nearly as crisp at the highest polish.


David

In my own noodling I've noticed very little difference in use between the diamond pastes and silicon carbide at the finer polish levels when used on a strop. I know this might not jibe with others findings but is what I observed. The SiC performed a bit better than the alumox, and the diamond not much different from the SiC. Which isn't to say they didn't perform well, just that they didn't perform as well as they do on lower carbide steels.

When I switched to a diamond lapping film the results were night and day from the diamond on a strop, and from now on this is how I'll handle all of the higher carbide steels if gunning for a bright finish. There's no downside as far as I can see, the 6u made a finer finish than the DMT EEF at 3u, and the 1u made a virtual mirror finish - I didn't bother going to the .5u yet. This compared to the 1u diamond compound coming off the DMT EEF barely improved the edge though did brighten it up some.

I still believe they perform a lot better at a rougher finish as it seems to compliment the carbides as a cutting feature in their own right, and not just as a wear resistant stretch of the edge done to a finer level (if that makes any sense). I'd swear some of my carbon steel knives can outlast or come very close to outlasting the s30v when done to a bright finish. Stop at 600 or 800 grit and the s30v will go a long time without needing any care - same with D2.

 

[Obsessed with Edges]

HH,

I'm noticing the bigger difference when using the diamond pastes on harder backing; most often on wood, or a single sheet of paper over wood/glass/stone (should've added this before), as opposed to using it on leather or other typical strops. Obviously, all my other compounds perform better this way (generally), but the SiC/AlOx still doesn't quite hit the threshold that the finer diamond does on S30V. This sounds somewhat like what you're seeing with the diamond lapping films (assuming on harder backing).

When I first tried diamond paste for stropping, I used it on leather, and didn't see much advantage over using other compounds on leather. I think leather backing is just a bit too soft to let the diamond work as well as it could (makes me see why DMT recommends using it on balsa or MDF). Didn't really open my eyes until I started using diamond on wood (balsa/basswood/oak; I've liked it best on the basswood). The 3µ diamond in particular really impresses me; there's a big jump in polish, when transitioning below DMT's EF (9µ) or 6µ paste, down to the 3µ paste, with a corresponding jump in sharpness. The 1µ paste sort of fine-tunes it, beyond that.


David

 

[HeavyHanded]

David, I was using the diamond on my Washboard with a single sheet of copy paper. Went heavy, went light, I could see the steel coming off, but the effect was just not there compared to the lapping film - I attributed this to the abrasive being locked in place on the film (though with a bit of up and down mobility).

This jibes with what I've noticed in the past re diamonds on other steels relative to other polishing compounds and was underwhelmed in those cases too. Not that it didn't perform well, but it didn't outperform any other contenders and in some cases was bested by them (AlumOx and SiC).

If you get a chance to test some of the diamond lapping films on the higher VC or Chromium carbide steels, by all mean do so (and if you already have and decided they weren't very effective, just ignore that), especially over a harder backing. I have no doubt the diamond paste works, but the films were a lot better in my hands.