Does Sharpening with a Grinder Ruin Your Edge?

I have bought several high end pocket knives including some in M4 and one especially I'm pretty sure chipped bad and needed several sharpenings before it suddenly became my favorite knife. As of yet I haven't seen any chipping or edge rolling in any of my knives including the pass around test knives. I also have leaned the shoulder on the hollow grind of the pocket knife I had chipping issues with and belt sharpened it a few times without the problem returning. I use sharp new belts when sharpening and while I have done it dry now I wet the belt as well. I'm not saying that this is proof that no damage is being done but that probably there is some real negligence with sharpening commercial knives. I think slow speed, a light touch and sharp wet belts help to minimize damage but it would be interesting to see someone come up with a test that checks the difference. Also a last thought is that one of the so called advantages of belt sharpening is the convex edge that is supposed to be tougher. If I recall correctly from the CATRA paper it was found that a finer edge last longer. If one is going to do a test there should be some sort of control to make sure that the edges are the same or else the test is flawed from the start.

Great article Larrin. Thanks for putting it together.
 
JG Custom Metal Works said:
My only complaint is the rust issue with my grinder(KMG). Does anyone use a water additive to prevent rusting? I’m thinking I might just spray paint my grinder with rustoleum and be don’t with it. Any advice on this issue would be appreciated.
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I'll occasionally peal off the thick layer of dusty shmoo off my grinder and find that yes, it is quite rusty. I don't care. It works and it makes me money. When the rust on the tool arm gets bad enough that it doesn't slide in and out smoothly I'll scrape it off. We put a KMG outside to grind dusty nasty stuff and for high speed deburring that makes a lot of dust and mess. It got pretty rusty too. I don't care.

Years ago I did use rust preventative in the water to prevent rusting the knives. Pretty much anything you use will leave residue that builds up and the stuff I was using would get funky smelling.

My advice would be don't worry about the grinder, it will be fine.
 
Ocelot85 said:
You're coming after Larrin for bias when he only posted the data he and others found and reported from independent third party testing. You've shown no actual data to support your belief besides relaying your own past anecdotal experiences in a non-quantifiable way since you didn't actually test anything to verify the results and record them.

You keep speaking about factors such as sharpening time which have absolutely nothing to do with the topic, the paper speaks only to one specific variable which is edge retention between different sharpening methods. All other factors that make your life more enjoyable or the process more expedient are completely and totally irrelevant to the subject.

Also you talk about the scientific method and fairness, yet your bias is as blatant as it could possibly be. If you disagree with the data set out to disprove it with the scientific method that you claim to care about. Set up a testing procedure and show us your data. Since you're a aerospace engineer I'm sure you'll design a procedure that will eliminate personal bias and show us verifiable proof of your claim. I look forward to seeing your paper on the topic.
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Did I strike a nerve? Good, that was the point. Why? Because nearly everything you're bashing me for, you can go right ahead and bash Larrin for too. ;) Check your emotions and alliances for a moment, keep your post in mind, and go back and read his article again. You'll see what I am saying. I am playing "Devil's advocate" here for good reason. Larrin is fresh out of school, and still learning. All I am trying to highlight here is that he's not giving fair chance to the complete picture. A technical review committee would tear him apart for this! Been there, done that, on both sides of the fence. Larrin can either think me an ass for this (which will surely be his initial reaction), or he can learn to be more objective and learn from it. The latter comes with time and experience. We call it wisdom.

Yes, I am bias towards using the grinder, my time is valuable to me and my personal experience has shown that I don't suffer appreciable edge retention as a result. That doesn't mean that I don't ocassionally shapen by hand, both for therapeutic reasons and to stay proficient. While I could absolutely set up and run the experiment you suggest, I have zero intention of doing so (and to answer your next question, yes, I have published several technical papers over the years, and typically write 2 technical reports every year, averaging 100 pages each). Why not? Because I already have the data to back my claim, and while it may be personal experience and not necessarily quantitative data, as I mentioned previously, it IS good enough data to prove the point. TO ME. Yes, nobody else will believe it until they do it themselves, and I don't expect them to, nor do I expect them to believe me. But I have a valid point here, and anyone that's being objective about the situation should see that. Shouldn't you require that Larrin do his own experimentation and generate his own data to back his claims if you ask that of me? Why does he get a pass and I don't? Bias? O_o
 
SpyderPhreak said:
Did I strike a nerve? Good, that was the point. Why? Because nearly everything you're bashing me for, you can go right ahead and bash Larrin for too. ;) Check your emotions and alliances for a moment, keep your post in mind, and go back and read his article again. You'll see what I am saying. I am playing "Devil's advocate" here for good reason. Larrin is fresh out of school, and still learning. All I am trying to highlight here is that he's not giving fair chance to the complete picture. A technical review committee would tear him apart for this! Been there, done that, on both sides of the fence. Larrin can either think me an ass for this (which will surely be his initial reaction), or he can learn to be more objective and learn from it. The latter comes with time and experience. We call it wisdom.

Yes, I am bias towards using the grinder, my time is valuable to me and my personal experience has shown that I don't suffer appreciable edge retention as a result. That doesn't mean that I don't ocassionally shapen by hand, both for therapeutic reasons and to stay proficient. While I could absolutely set up and run the experiment you suggest, I have zero intention of doing so (and to answer your next question, yes, I have published several technical papers over the years, and typically write 2 technical reports every year, averaging 100 pages each). Why not? Because I already have the data to back my claim, and while it may be personal experience and not necessarily quantitative data, as I mentioned previously, it IS good enough data to prove the point. TO ME. Yes, nobody else will believe it until they do it themselves, and I don't expect them to, nor do I expect them to believe me. But I have a valid point here, and anyone that's being objective about the situation should see that. Shouldn't you require that Larrin do his own experimentation and generate his own data to back his claims if you ask that of me? Why does he get a pass and I don't? Bias? o_O
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He presented information, from actual studies and testing. You presented opinions, with no factual backing from testing or studies. You're not playing devils advocate, you're upset because your bias was challenged. That's totally fine, if you don't like the information you can set out to disprove it with your own studies. Simply stating your opinions and anecdotal experience means absolutely nothing to the rest of us, find or generate factual information from testing to compete against what he stated.
 
Ocelot85 said:
He presented information, from actual studies and testing. You presented opinions, with no factual backing from testing or studies. You're not playing devils advocate, you're upset because your bias was challenged. That's totally fine, if you don't like the information you can set out to disprove it with your own studies. Simply stating your opinions and anecdotal experience means absolutely nothing to the rest of us, find or generate factual information from testing to compete against what he stated.
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I'm not upset at all, and I frankly couldn't care less what someone else thinks, because I have already proven to myself what works for me. Anyone could do the same for themselves. I'm just pointing out that he didn't present a complete picture, and there's more to the story here. Take it or leave it. That's playing Devil's advocate. I didn't write his article, so why should I have to generate that missing data for him? I shouldn't, and he should do it. If he couldn't find the data, then say so, or produce your own. The reader has no responsibility to do that for him. As written, his article is biased and incomplete, drawing a somewhat incorrect conclusion due to the missing data.
 
SpyderPhreak said:
I'm not upset at all, and I frankly couldn't care less what someone else thinks, because I have already proven to myself what works for me. Anyone could do the same for themselves. I'm just pointing out that he didn't present a complete picture, and there's more to the story here. Take it or leave it. That's playing Devil's advocate. I didn't write his article, so why should I have to generate that missing data for him? I shouldn't, and he should do it. If he couldn't find the data, then say so, or produce your own. The reader has no responsibility to do that for him. As written, his article is biased and incomplete, drawing a somewhat incorrect conclusion due to the missing data.
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Larrin has no responsibility to do anything for anyone else here when it involves his article or website www.knifesteelnerds.com, if you don't like his information it's on you to dispute it with verifiable facts if it's that important to you. Otherwise state what you believe as your opinion, agree to disagree and let it go.
 
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Ocelot85 said:
Larrin has no responsibility to do anything for anyone else here when it involves his article or website, if you don't like his information it's on you to dispute it with verifiable facts if it's that important to you. Otherwise state what you believe as your opinion, agree to disagree and let it go.
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Well, this isn't Larrin's site. ;) If it's not his responsibility to to present the data, it sure as hell isn't mine! :rolleyes: You seem to have lost sight of something; I'm not disputing any of his facts or data. I am saying that what he's presenting is an incomplete picture, and therefore he draws an incorrect conclusion by saying that grinding ruins an edge, when that isn't always true. That's NOT for me to do anything with. He can fix it if he chooses, or leave it as is. I am just making sure folks don't treat what he is saying as gospel, since it is incomplete.

I am not wrong in this, so please stop trying to downplay what I am saying. I'm sure Larrin can comment himself, as he has clearly been reading this. I would love to hear from him instead, he doesn't need you to keep running interference for him.
 
If I waited for every missing piece of information before publishing an article I would never post anything. I have no personal stake in what the best way to sharpen a knife is. But the knifemakers arguing with me certainly do. The accusations of bias are rather ironic.
 
Larrin said:
If I waited for every missing piece of information before publishing an article I would never post anything. I have no personal stake in what the best way to sharpen a knife is. But the knifemakers arguing with me certainly do. The accusations of bias are rather ironic.
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Acknowledge that there is missing data then, don't just ignore it altogether. I have no stake in this either, but I do think that the whole picture should be acknowledged for the benefit of the community.
 
SpyderPhreak said:
Acknowledge that there is missing data then, don't just ignore it altogether. I have no stake in this either, but I do think that the whole picture should be acknowledged for the benefit of the community.
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You are implying that I have intentionally misled people by hiding something. That is not the case.
 
My apologies Larrin. I have sent a message to both parties to knock it off.

I personally use both stones and a belt. 95% of blades get sharpened on a belt. I grind very slow, and in some cases use a Kool-Mist. Stones finish the job on some knives, like yanagi-ba.
On most blades I sharpen for chefs, they say they never had a blade as sharp and an edge that lasted so well.

I think the biggest problem with belt sharpening is using non-VS grinders and the wrong type belt. Too fine and the belt heats the apex of the edge easily.

SLOW speed with mist lubrication is almost like using a stone.

I did find your article interesting. Thank you for writing and posting it.

Where I see it causing disagreement is that everyone has different belt grinding parameters, so it is hard to quantify the results of belts beyond the ones used in the tests. Stones are pretty universal, so the data on stones can be considered more-or-less universal. I don't think anyone would disagree that a stone can get the best edge. I wouldn't say that using a belt "ruins" the edge, but done wrong it can be far worse than a stone edge. How close you get to a stone quality depends on your skills and equipment. Your article shows where to work on the process to improve one's edges and sharpness.

I think the best summation is YMMV.
 
Larrin said:
You are implying that I have intentionally misled people by hiding something. That is not the case.
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Your thread title and article DO imply that using a grinder ruins the edge. That is not the always case! Maybe acknowledge that using a grinder doesn't always ruin an edge?

Stacy E. Apelt - Bladesmith said:
Where I see it causing disagreement is that everyone has different belt grinding parameters, so it is hard to quantify the results of belts beyond the ones used in the tests. Stones are pretty universal, so the data on stones can be considered more-or-less universal. I don't think anyone would disagree that a stone can get the best edge. I wouldn't say that using a belt "ruins" the edge, but done wrong it can be far worse than a stone edge. How close you get to a stone quality depends on your skills and equipment. Your article shows where to work on the process to improve one's edges and sharpness.

I think the best summation is YMMV.
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This is what I have been trying to get across here. And yes, I also acknowledged that it can go badly quickly.

I'll bow out of the discussion now.
 
SpyderPhreak said:
Your thread title and article DO imply that using a grinder ruins the edge. That is not the always case! Maybe acknowledge that using a grinder doesn't always ruin an edge?
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The title is a question. The article says that using water cooling prevents overheating.
 
Thank you SpyderPhreak for letting it go.

BTW, on the subject of belt sharpening, when I use a mist spray, I use the Kool-mist cutting/lubricant additive ( concentrate). It seems to work well. The mist itself is very cold. If the air pressure and flow rate balance are set right, the mist doesn't even get things particularly wet. It sort of evaporates as it cools things.

I will have to make a test and see how cold the mist makes a blade, but I can tell you it will make your fingers really cold if they get in the direct spray

For those doing grinding post-HT and belt sharpening I can't think of a better accessory that a mist spray system.
 
SpyderPhreak has a good point. "Does Sharpening with a Grinder Ruin Your Edge? " the answer is no, of course not. Only most of the time.

Some folks might read this thread as indicating that makers who sharpen on belts are doing it wrong (this harkens back to the old quench oil wars) when the reality is almost the only way to sharpen knives in production is using a belt powered grinder and it can be done on a powered belt grinder without overheating the edge, except the vast majority of folks sharpening on a powered grinder are, in fact, damaging their edge.

You can do it really slow. Or better, slow and wet. But most folks don't. So, yes, powered grinding can wreck an edge. Most of the time. But it is not universally a bad approach and in reality it is the only approach for folks doing it in production. So the answer to the thread "Does Sharpening with a Grinder Ruin Your Edge", the answer is no. Despite that fact that most of the time it is "yes".
 
bmilleker said:
Do you know the speed the belt was moving in his tests? Assuming a fast speed, I would love to see the same tests done at a slow speed, and then again with cooling.
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I asked Roman these types of questions years ago on the hypefreeblades forum (what pressure was used, feed rate, how sharp were the abrasives, etc) but got no answer. These are all factors.

And for those questioning sweeping conclusions drawn by Larrin, the articles states that "Hand sharpening or water cooled sharpening are the best methods for preventing overheating of edges" it doesn't make the conclusion that it absolutely beyond doubt will prevent any temper damage.
 
Larrin, do you know how the tap was ground? I know when I send my end mills out for sharpening they come back brown at the edges sometimes, which I'm guessing means they probably don't use coolant.

Sharp abrasives vs. dull are key as well I when it comes to belt sharpening... For example, the trizact gator belts will "glaze" over and generate more heat than if they are freshly dressed.

I set up my water cooling system based upon Nathan's, he did a great job describing how to set it up without making a mess. I find that I rarely need to use my chiller platen, even with the rubber backing belt, I just set up a second mister to hit the inside of that belt to lube it and everything stays surprisingly cool. I do use Kool mist coolant as it helps prevent rust on carbon steel blades (not completely, but much better than straight water).
 
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