Stone wear

sickpuppy1

sickpuppy1

Joined
Sep 27, 2018
Messages
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I realize the answer to this has a lot of variables,but I'm asking anyways.
I bought a set of GritOmatic SIC stones for my M2. the 120 and 240 don't have the name on the stones (gritomatic) but the 400,600,1000,and 2500 all have the name stamped on the stone itself, as well as name and grit on the back too. My question is, how long do you think the name would stay on the stones? I ask because I wonder if I'm pressing too hard or not hard enough is the only reason. Just trying to gauge things overall. I realize it varies if I'm re profiling or just touching up an edge. I've done 6 knives so far and did a 2-3 degree change on 2 of them,5 degree on another and touch ups on the other 3. I can still see the name clearly on all of them but its starting to blur alittle on the 1000 and 2500. So as I see it, not much wear at all.
Thoughts?
 
sick, I don't own that brand of SiC stones. I do have a Norton and Carborandum brand. The finer one goes with this type grit the less wear
is shown on the stone. The 400 and up packs tightly together. The 120 coarse grit stone is where you'll see a lot of wear. DM
 
David Martin said:
sick, I don't own that brand of SiC stones. I do have a Norton and Carborandum brand. The finer one goes with this type grit the less wear
is shown on the stone. The 400 and up packs tightly together. The 120 coarse grit stone is where you'll see a lot of wear. DM
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No...that's actually the opposite of what's true from a manufacturing standpoint. The finer the grit is, the greater the grit/bond ratio becomes and the softer the stones start getting at a given press rate for the vitrified abrasive. The fact that your experience with the coarse stones is that they're softer has to do with the formulation of those particular stones rather than an inherent property of stones in a general sense. This is actually part of the reason why Japanese water stones are so notoriously soft. Yes, it's partly their philosophical approach their sharpening process, but it's also largely integral to the vitrified bonding process as a manufacturing dynamic. You can't make hard fine abrasives easily, especially above ANSI 400, as the mix becomes more like thin pancake batter in the pre-fired state and so cannot be so readily compressed like it can be when it behaves more like wet fine sand.
 
Ok, so with that in mind, and higher grit, say the 1200-2500, and after 6 knives the ink of the brand name is barely even smeared, I’m not pressing too hard. And maybe even a bit soft?
 
FortyTwoBlades FortyTwoBlades It seems that somehow Boride Engineered Abrasives gets around the problem you describe, as the finer stones through F1200 (~J4000) do not seem softer than coarse stones of the same series. Some are treated but others are "naked" like the silicon carbide CS-HD stones.
 
I have had the same thing happen with higher grit stones as well,I find the same thing you do that the lower grit stones tend to wear a a bit faster.

sickpuppy1 said:
Ok, so with that in mind, and higher grit, say the 1200-2500, and after 6 knives the ink of the brand name is barely even smeared, I’m not pressing too hard. And maybe even a bit soft?
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Mr.Wizard said:
FortyTwoBlades FortyTwoBlades It seems that somehow Boride Engineered Abrasives gets around the problem you describe, as the finer stones through F1200 (~J4000) do not seem softer than coarse stones of the same series. Some are treated but others are "naked" like the silicon carbide CS-HD stones.
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Again, it's a formulation of other variables involved rather than being specific to the grit size. Stones may be made harder or softer by adjusting the compositional variables and how they're processed. But as a rule of thumb, if all else is held constant then the shift to a finer grit results in a softer stone, at least where vitrified bonds are concerned.
 
I don't exactly get your question. The dye goes deep into the stone. I would judge stone wear by how much grit seems to be coming off the stone with a few passes AND how much the stones are dishing over time judged with a straight edge across the surface of the stone.
That said here are a couple of vids taking about why stones wear and how steel types can effect that and how force applied relates.

This vid skip ahead to 4:40 minutes in. (he says what that stone is at 3:40)
 
FortyTwoBlades said:
But as a rule of thumb, if all else is held constant then the shift to a finer grit results in a softer stone, at least where vitrified bonds are concerned.
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I won't argue that
but
My high grit stones : Shapton Glass 4,000, Shapton Pro 8,000 and 15,000 Norton 8,000 tend to hardly wear at all and do not need flattening near as often as the much more coarse stones down in the 200 to 1,000 range.
Probably because the edge is apexed at that point and the force applied is lower.
(here it comes, you knew it was coming : That and I use sharpening jigs so I am not inadvertently digging into the stones while hunting around trying to get on the edge as I would be while hand sharpening.)
 
If you are not pressing down hard enough the stones will glaze over and not cut as well, too hard and they will wear prematurely. This is VERY general advise, there are lots of variables, nearly all are related to the stone in use. I tend to use light pressure when I use vitrified stones and have yet to have one glaze on me, all are EP. If you do get one to glaze a quick dressing with loose abrasive on a flat plate will fix it.

The coarser stones do more work and when they shed abrasive grains they are much bigger, hence more wear.
 
Wowbagger said:
I won't argue that
but
My high grit stones : Shapton Glass 4,000, Shapton Pro 8,000 and 15,000 Norton 8,000 tend to hardly wear at all and do not need flattening near as often as the much more coarse stones down in the 200 to 1,000 range.
Probably because the edge is apexed at that point and the force applied is lower.
(here it comes, you knew it was coming : That and I use sharpening jigs so I am not inadvertently digging into the stones while hunting around trying to get on the edge as I would be while hand sharpening.)
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That's a whole bunch of other variables. Again, it applies specifically to vitrified bonds with all other variables held fixed (other than the necessary change to the grit/bond ratio because otherwise they'd fall completely apart.) Other bond types can be used, including different kinds of binder within vitrified bonds, let alone shifting to different bond types entirely. Then there's structural changes like the density vs porosity of the stone. You can have hard fine stones. But it requires adjusting other variables than just the grain size. Making the grain size finer makes the stone at a given mix softer, not harder. Think of it like walking on riprap or cobblestones vs walking on sand. Another way of thinking about it is that if you take a formulation and make the grit coarser it will behave harder. But you can make a soft coarse stone or a hard fine stone. There's just a lot of interrelated variables that impact that so you have to adjust those totally different variables to achieve those results.

Say Stone A has a medium hardness at the same grit size as Stone B, which is a hard bond. Reduce the grain size without changing anything else and you may very well make Stone A a soft bond and Stone B a medium bond instead. This is simply describing how grain size relates to stone hardness because the assertion was made that coarser stones are softer. That's not inherently true. While it's very possible to make coarse stones that are soft, and many are, it is not because it is using coarse grains.
 
Stone mfg process is one I hadn’t even considered. I was asking a long winded version of how do I know if I’m pressing too hard or not hard enough, erring to soft pressure rather than too hard.
I actually believe I’m going too soft(story of my life,lol) and figure worst case it takes longer. I’m going to watch the vids once I get home.
 
It's different with every stone, and just takes experimentation to figure out what works best. Few manufacturers list a suggested pressure, and even those that do can only give you a vague sense compared to just trying it out for yourself. :)
 
David Martin said:
It is likely I work a blade more on the coarse stone, removing metal & setting the bevel than on the finer stone. DM
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Very often the case. I can tell you that I go through coarse grinding belts 5 to 1 with my medium belts, and have seldom had to replace my fine ones.
 
I first use a coarse Venev diamond stone, about 160 microns, to establish the apex. Then, I switch to the SiC stones for the remainder of the sharpening. Since the diamond stone remains flat and doesn't wear, I find this method saves lots of time and money.
 
S.T.A.T.E.S. said:
I first use a coarse Venev diamond stone, about 160 microns, to establish the apex. Then, I switch to the SiC stones for the remainder of the sharpening. Since the diamond stone remains flat and doesn't wear, I find this method saves lots of time and money.
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It does, though. Just slowly. Abrasives do wear and blunt over time. Because it's super hard, diamond does take much longer to wear than other abrasives, but it does wear.
 
FortyTwoBlades said:
It does, though. Just slowly. Abrasives do wear and blunt over time. Because it's super hard, diamond does take much longer to wear than other abrasives, but it does wear.
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Yes, you are right. Diamond does wear but much, much more slowly. Specifically, the Vickers hardness of diamond is 112 GigaPascals whereas SiC is only 24.5 GPa. SiC doesn't even achieve the "superhard" category by the traditional tribology standard of hardness > 40 GPa on the Vickers scale. When using diamond for high speed machining of tool steel, it does show wear, but how many years would a normal person take to put 1,000 linear miles on a stone?

Edit: I estimate that it would take 8 years of 2 hours of sharpening at 1 stroke per second for 365 days per year before the diamonds showed wear. Usually the substrate is what wears, often from pressing the diamonds deeply into the soft steel and tearing them out of their adhesive substrate. Best to let the weight of the diamond stone do the work and not apply additional pressure.
 
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