Difference in Sharpness: CV and 1095

[DEPBID]

Hello folks. I use the Sharpmaker with the ultra-fine rods, then finish up with black and green compound on a leather strop. I test my edges with phone book paper (the smoother/quieter the blade passes through the paper, the sharper, right?)

I've got some CV steel on a Case knife built in the 70s that will slice through the paper like butter and some 1095 on a Great Eastern Cutlery knife that slices pretty well, but not as quietly as the case.

Is that just the nature of the steels, or my shortcomings as a sharpener? Does 1095 require a slightly different technique?

I suppose it doesn't really matter, both steels get sufficiently sharp, but it has me wondering.

Thanks

 

[Obsessed with Edges]

I've learned that very small differences in the blade/edge geometry have a bigger impact on ease/smoothness/quietness of slicing, especially when comparing two very similar carbon steels like 1095 and CV. Both of these steels can be made wickedly sharp, but very subtle differences in the cross-sectional shape of the edge can make one or the other stand out. Two seemingly identical blades, but one that's just a little thinner-ground than the other, can show a noticeable difference in slicing. A big difference can be seen simply by convexing the shoulders (only) on an otherwise V-bevelled edge. I never knew how 'noisy' the extra drag of the V-bevel's shoulders are in cutting paper, until I smoothed 'em down the first time. Slicing became immediately quieter and slicker.

Other differences between steels, like the alloying elements and heat treat, can and will usually impact the perceived 'ease of sharpening', which can lead one to believe one steel can't be made as sharp as another. They usually can be, but the difference is in the time required to fully finish the job. It's easy to be discouraged by the extra time & effort required in attempting to sharpen a really abrasion-resistant steel, and give up on it before the edge is completely apexed and finished. Other steels may sharpen fairly easily, but be more prone to forming wire edges (420HC, VG-10, ATS-34), which if not recognized and properly dealt with, will make a blade seem to go dull very fast (wire edge folds over).

Regarding the two knives you've compared ('70s Case CV and current generation GEC 1095), I'm pretty sure the Case blade is likely hardened to lower RC. It's been known that many of the older knives weren't hardened to the same degree as more modern makes. Some old ones have even been RC tested in the 40s on the scale. Between these two knives, I'm betting the difference in 'ease of sharpening' is impacting the results you're seeing. I have a 1965 vintage Case Folding Hunter (6265 SAB), which sharpened up easily & fast, and took an amazing edge. It did seem almost disturbingly 'soft', using diamond hones, compared to the modern blades I've sharpened. But it slices like crazy (I convexed the shoulders of the bevel, BTW), and holds it's edge surprisingly well.

 

[DEPBID]

Thanks David, I was hoping you'd chime in.

I'll keep with it--that's part of the fun. Sounds like convexing the shoulders is my next step.

Have you noticed that the soft steel on you Folding Hunter loses its edge sooner than more modern blades with higher RC?

 

[Obsessed with Edges]

Thanks David, I was hoping you'd chime in.

I'll keep with it--that's part of the fun. Sounds like convexing the shoulders is my next step.

Have you noticed that the soft steel on you Folding Hunter loses its edge sooner than more modern blades with higher RC?

I haven't noticed that yet. That's not to say it won't lose it's edge sooner, but I haven't really pushed it that far. After sharpening it up to tree-topping hairs, I used it to shred a cardboard Priority Mail box that was laying around. Cut the box into strips about 1/2" wide, until none was left. Considering how 'soft' the steel felt on the hones, I was surprised to see it still tree-topping after finishing that. I would've expected to see some degradation of the edge, but couldn't tell that anything had changed. That made me re-think a little bit, about the factors that really affect edge-holding. It's sort of a fundamental principle with steel, that the carbon content has greater influence on edge-holding than all other factors, with the heat treat being next-most important. Being that this blade has at least 0.8 % carbon (assuming Case's old carbon blades are the same exact CV composition), I've begun to look more closely at carbon content when comparing different blades, as opposed to just looking at the RC hardness numbers alone. I also believe the edge's shape (such as convex) really does impact the durability of it, as well as cutting performance. Especially in an example like this, with a supposedly 'soft' blade. I feel like I really learned a lot with this particular knife, which is why I continue to be fascinated by all this.

 

[Kbrasmodeler]

I haven't noticed that yet. That's not to say it won't lose it's edge sooner, but I haven't really pushed it that far. After sharpening it up to tree-topping hairs, I used it to shred a cardboard Priority Mail box that was laying around. Cut the box into strips about 1/2" wide, until none was left. Considering how 'soft' the steel felt on the hones, I was surprised to see it still tree-topping after finishing that. I would've expected to see some degradation of the edge, but couldn't tell that anything had changed. That made me re-think a little bit, about the factors that really affect edge-holding. It's sort of a fundamental principle with steel, that the carbon content has greater influence on edge-holding than all other factors, with the heat treat being next-most important. Being that this blade has at least 0.8 % carbon (assuming Case's old carbon blades are the same exact CV composition), I've begun to look more closely at carbon content when comparing different blades, as opposed to just looking at the RC hardness numbers alone. I also believe the edge's shape (such as convex) really does impact the durability of it, as well as cutting performance. Especially in an example like this, with a supposedly 'soft' blade. I feel like I really learned a lot with this particular knife, which is why I continue to be fascinated by all this.

Hey, David, how fine do you refine the edge? I find that my edges seem to last longer when I polish more. My longest lasting edges com from 1,500-2,000 grit sandpaper, followed by stropping on chromium oxide. It looks like a mirror, cuts like a demon, and lasts a long time. Do you find smilar results?

 

[Obsessed with Edges]

Hey, David, how fine do you refine the edge? I find that my edges seem to last longer when I polish more. My longest lasting edges com from 1,500-2,000 grit sandpaper, followed by stropping on chromium oxide. It looks like a mirror, cuts like a demon, and lasts a long time. Do you find smilar results?

Up to ~2000 grit, plus some polishing on strops with Simichrome or diamond paste has worked pretty darn well by me. With wet/dry paper in particular, it's pretty easy to take it that far and get a respectable 'mirror' without getting too hung up on making it perfectly polished. I've found anything above that becomes too much of a hassle to keep it that way, as the slightest and smallest particles of dirt/dust/grit from stones will scuff it up again. From a functional standpoint, these edges are great cutters too, and very simple to maintain on strops with compound.

I've started to experiment with 'working edges' at something lower in grit (currently with ~800), just to see the differences in how an edge like that cuts. The slightly more toothy edge does well also, and I've found it to be a very quickly-attained edge too, as well as simple to maintain by stropping on the rough side of my leather belt. From a 'simpler is better' standpoint, this seems to be a very good compromise.

Whatever the finishing grit, I firmly believe the quality/purity of the apex itself is what really makes a great edge. If the two bevels meet cleanly and perfectly at the apex, and any burrs or wires are cleaned up and eliminated, that's what makes an edge really pop.

 

[db]

I'd agree the edge shape really does make probably the biggest difference. We all know that the Vic SAKs have soft short lasting edges right? I put a shallow convex on a Cadet an already fairly thin blade. My shallow convex edge goes up almost half way up the blade thinning it and convexing it. I'm amazed at how much longer a very sharp edge lasts on this little Vic. Cadet. It has been a main carry of mine for the last few years, and the edge holding is as good as any other edge. When it does need a touchup that is quick and easy. A few strops or if I wait too long a stroke or two on a hone and I'm back to sharp.

 

[Obsessed with Edges]

I'd agree the edge shape really does make probably the biggest difference. We all know that the Vic SAKs have soft short lasting edges right? I put a shallow convex on a Cadet an already fairly thin blade. My shallow convex edge goes up almost half way up the blade thinning it and convexing it. I'm amazed at how much longer a very sharp edge lasts on this little Vic. Cadet. It has been a main carry of mine for the last few years, and the edge holding is as good as any other edge. When it does need a touchup that is quick and easy. A few strops or if I wait too long a stroke or two on a hone and I'm back to sharp.

For some reason, I hadn't (yet) considered trying a shallow convex on a SAK blade, but it sounds intriguing. Bet it looks good, too. I'd noticed the benefit of a real shallow convex on a couple of Opinels I thinned out, so I have no doubt it could do some nice things for a SAK too.

 

[db]

I think you'll find it does work just as well on a sak as on an Opinel. In fact that is what I was really trying to do. Make the SAK cut as well as my Opinel. I really am a big believer in the shallow convex edge. Easy to maintain, cuts better, and I think they just look cool.