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Best way to sharpen O1?
- Thread starter Ferahgo
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Looking at the site from which the chart was linked, it also mentions the chart was generated for Cubic Boron Nitride (CBN) grinding wheels, so the 'grindability' estimates might be skewed a bit. With CBN wheels on powered grinders, I'd expect most steels to be easy to grind that way, as compared to doing it by hand.
It might also take into account the actual size of the carbides too. The CPM steels have much smaller carbides (albeit they're harder vanadium carbides) than something like D2 (it's chromium carbides can be huge, up to ~50µ or larger), so smaller carbides will usually be easier to grind out of a (softer) surrounding steel matrix, even if they're harder than the great big chromium carbides in D2. The CPM process was created to make very wear-resistant steels easier to grind, by making the carbides smaller and more evenly distributed throughout the steel. I'm giving the benefit of the doubt in assuming there's at least some validity to the referenced chart, but who knows...
David
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Why?
The chart says it has "high grindability" not that its "extremely easy to grind" ... whatever those things mean
This what the text accompanying the chart says
http://www3.telus.net/BrentBeach/Sharpen/jig%20faq%2006.html#ts6 said:
Then
http://www.crucibleservice.com/eselector/prodbyapp/tooldie/cpm10vt.html said:
So is CPM10V in the wrong place (easy/high grindability)?
Probably not , UAMA ought to know their products ... i dont know
Does that mean 10V is easy to "grind" on a benchstone or beltsander?
Probably not but i dont know
However, if you have to "grind" a knife instead of merely sharpening ...
From reading articles by Phil Wilson yes it's very hard to grind to the point he refuses to make kitchen knives in it anymore because of the size and a sic belt will be shot in a couple passes on a small hunter. That's why I thought that was funny. I've never ground or sharpened 10v but I presume it's more difficult than any of the other steels in that chart
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Ok, I see that
Not exactly surprising, SIC is friable .... he also posts pics of grinding on belts without coolant/lubricant, so ... not lubricated wheels ...http://www.seamountknifeworks.com/articles/CPM_10V.pdf said:
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This is the correct answer, the knife needs a secondary bevel to allow easier sharpening. My thinking is you have not fully apexed the knife because it takes much longer to remove the amount of metal necessary for such a wide edge bevel.
Take a few passes grinding the edge directly into the stone to blunt it, note the light reflecting at where the apex should have been. Then you must grind until all this light has stopped reflecting, actually just slightly more passes than it takes for this. At this point, even off a very coarse stone the knife should be shaving sharp if you have fully apexed it. If it does not do this, you haven't fully apexed and you need to keep grinding. Don't move on to finer stones unless you have achieved this.
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This is why I mentioned the chart was possibly skewed relative to using CBN grinding wheels. SiC is less hard than the tons of vanadium carbides in 10V and similar steels. Combine that with the friability of the SiC, and it's no wonder it doesn't work well. CBN is much harder than vanadium carbide, and it's also less prone to breaking down under high heat generated from powered grinding, so it's usually recommended for grinding such wear-resistant steels.
David
Oh I'm sure cbn is a very good abrasive for high vanadium steels as its almost as hard as diamond. But that doesn't mean it'll cut 10v easier than o1. It'll cut 10v easier than aolx would. Even diamond abrasives cuts high wear resistant steel slower than low alloy steel it just closes the gap more than a normal stone. And sic is still harder than vanadium carbide. Not by much though. That's why sic abrasives is considered a minimum for these steels. Other than the last two entries the chart looks right. It places m4 in a harder to grind area than o1 which is correct. If what's being said here is the case that cbn cuts 10v easier than o1 than the list would show m4 as being easier the grind than o1 but it is in its proper place. I think the chart is a typo and the last two entries should be in the top
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SiC is almost as hard as vanadium carbide, but still less-hard. Per Norton's chart below:
SiC can still grind vanadium carbide steels by digging or 'scooping' them out of the matrix steel, as opposed to acually grinding or abrading the vanadium carbides themselves, which it won't do well, if at all. But it'll still be less efficient doing it and will be worn by it.
The earlier referenced chart does make me scratch my head a bit; the O1 measure being part of that. There may be other factors in how they arrived at their own conclusions, maybe due to loading/clogging of the abrasives by certain steels or other factors. For example, some lower-carbon steels are notoriously bad for clogging abrasive wheels & stones, which slows grinding to a halt at times. But again, who knows how they measured it...
David
SiC can still grind vanadium carbide steels by digging or 'scooping' them out of the matrix steel, as opposed to acually grinding or abrading the vanadium carbides themselves, which it won't do well, if at all. But it'll still be less efficient doing it and will be worn by it.
The earlier referenced chart does make me scratch my head a bit; the O1 measure being part of that. There may be other factors in how they arrived at their own conclusions, maybe due to loading/clogging of the abrasives by certain steels or other factors. For example, some lower-carbon steels are notoriously bad for clogging abrasive wheels & stones, which slows grinding to a halt at times. But again, who knows how they measured it...
David
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Ya I've read a chart that had the sic slighter harder. Oh well. The knife maker recommends sic stone on his blades including 10v so it must works but we've derailed the thread with our silly science. Lol. Yes I agree some cheap stainless which is soft and easy to grind can be gummy on the stones or belts even in its "hardened" state. In this case as long as the heat treat was done well there should be no problems. Even going non magnetic and quenching it while not going to get all the performance of o1 will still net a very good blade. I will disagree though on adding a secondary bevel when sharpening. That's going to make sharpening easier but will only make the thick grind of the knife worse. Of course my opinion as I don't like scandi grinds and see them as a way to get a knife out to a customer without the work of properly grinding the blade. And please makers who utilize this grind take no offense. You're making what your customers want based on how popular this grind is. I have a couple moras and I like them. I bought them because they were cheap and I could learn how to completely regrind a knife and not be too upset if I ruined it. To the op this long sharpening session was probably evening out the original grind and subsequent sharpenings should take a fraction of the time now that you have two even flat bevels
Ferahgo
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Don't worry about it. I enjoy the learning experience this has given me.
Bill DeShivs
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And look how wide your secondary bevel is!
The primary bevel is wrong on this knife. It's more like a cold chisel. The bevel should be at least twice as wide as it is, and it could actually go all the way to the spine.
As it is the knife is a flat pry bar with a chisel edge.
The primary bevel is wrong on this knife. It's more like a cold chisel. The bevel should be at least twice as wide as it is, and it could actually go all the way to the spine.
As it is the knife is a flat pry bar with a chisel edge.
Ferahgo
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The secondary bevel is actually shorter than it looks. The stropping took off some of the patina around it, so it looks wider than it is. And I won it in a GAW, so I will certainly not complain. It is a good knife that has served my well this far.
bodog
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It's kind of hard to see, is that a scandi grind? If so, you'd have to remove A LOT of metal to get to the apex. You can sharpen any steel with anything that's more abrasive than the steel. Maybe your stone is clogged. Take it to the sink and scrub it. O1 is not hard to grind. If you can't get it sharp then you're not hitting the apex and/or not removing the burr and/or rounding the apex when you strop. That's all it really ever is in any of these threads.
The reason you may not be hitting the apex is likely because of the stones you're used to using. They're slow to cut and quick to glaze. Clean them or buy a new set. Try a spyderco bench stone if you're used to freehanding. They're not that expensive.
The reason you may not be removing the burr is because a lot of the steels/knives you mentioned could form burrs that are easier to remove and that's what you're used to. With this one you may just be flip flopping the burr back and forth until it breaks off leaving a rougher, coarser edge. If that's the case sharpen until there's the smallest of small burrs on one side, do the other side the same way, then increase the angle by several degrees and very lightly make a couple of passes on each side to cleanly cut the burr off.
If you're rounding the apex then just keep a more consistent angle and make fewer passes when you strop.
The reason you may not be hitting the apex is likely because of the stones you're used to using. They're slow to cut and quick to glaze. Clean them or buy a new set. Try a spyderco bench stone if you're used to freehanding. They're not that expensive.
The reason you may not be removing the burr is because a lot of the steels/knives you mentioned could form burrs that are easier to remove and that's what you're used to. With this one you may just be flip flopping the burr back and forth until it breaks off leaving a rougher, coarser edge. If that's the case sharpen until there's the smallest of small burrs on one side, do the other side the same way, then increase the angle by several degrees and very lightly make a couple of passes on each side to cleanly cut the burr off.
If you're rounding the apex then just keep a more consistent angle and make fewer passes when you strop.