My other question is: will a millisecond of time over the blades temper actually cause any damage? In my previous comment I mentioned another maxamet blade, a native. I was amused to see the discussion on the sparks generated during grinding where they said that sufficiently fine particles will auto-ignite. Then I hone a smaller secondary bevel by hand. Then the other side was just as resistant. If that temperature is still exceeded then it wont matter, of course. There I saw examples of "great" driving for example, a quarter million dollar sports car, still displaying a temporary license plate, that had been wrapped around a cement park bench. I did a test with cardboard on a maxamet blade, and like the other comments said it got VERY hot, too hot to Touch for more than a second. I think belt grinders have their place. [2] Roberts, George Adam, Richard Kennedy, and George Krauss. I only use it wet to sharpen knives for the most part as grinding hardened blades wet makes a mess. On the order of 500-800 SFPM. due to the high rate of removal, very critical to know what one's doing. I have been trying to lower the bevel of my Cara Cara. We only do the work that is needed to fix your problem. The knife company GLOBAL compared their factory sharpened knives to whetstone sharpened knives and found a big difference [6], the information has since been removed from the website but I have hosted it here: GLOBAL CATRA testing. It's all about the operator. The knives or scissors were sharpened by hand on a grinder with 3M 220 grit Trizact belts. But, a knife seems to be warmed to 40C for 10 seconds and will detemper and soften. The use of steels capable of high temperature tempering treatments help to some extent since they can withstand more heat. Tempering is a time-temperature process, so short periods of time at high temperatures are equivalent to long holds at low temperatures. There are water cooled methods, such as the Tormek sharpener or adding a water misting system to a belt grinder: Using water cooling prevents steel from heating up during the grinding and polishing process and therefore may prevent overheating of edges and loss of edge stability and edge retention. I used it first on a cheap knife and the edge just kind of melted off. I won't argue that you always have to shoot for the ultimate edge and I won't say anyone who gets the results they desire is using a wrong method. Most certainly! And all evidence points to that being the case. JavaScript is disabled. Im certain that the Native did in fact hold its primary sharpness for much much longer than my pm2, both with maxamet. . Or is it just cardboard that makes the blade that hot? Measuring whether or not the edge has actually exceeded any given temperature is very difficult given that it is the very fine edge of the knife that we are interested in. 1000 grit does not warm the knife at all (by the touch). Consider a sharp knife and a dull knife. Particularly tool steels like Vanadis 4 Extra, 4V, 3V, and others. Finely divided powders of iron and steel can be dangerous if they are allowed to form a dust cloud or With cardboard there is a good chance the heat is being spread throughout the whole blade and not just the edge (I imagine a large portion of the friction coming from the primary grind). I have a Worksharp with the blade grinding attachment, and generally I use it to establish primary bevels only. My last exposure to chinesium was my treadmill and it was quite satisfactory. Become a patron and gain access to awesome rewards including early access to articles or a Knife Steel Nerds mug! Before stropping ot would still be hair popping arm hair. I might want to add that the first time I saw a Work Sharp grinder I thought to myself what a fast way to ruin the edge of your knife. Do you know to what degree belt speed plays a roll? People with skills can drive Honda Accords with no issues and use belt grinders on knives. It can take less than a second, or just a touch too much pressure, and you ruin the temper on a blade. Go on YouTube and search for "ruined knife sharpen" or something of that nature. regarding cooling systems, apart from the usual pressurized spray systems Ive seen the following method recommended: a tank above that drips water, via a copper tube, onto an arm mounted sponge that rotates down onto the belt. When you occasionally have in a place without power how could you sharpen a blade? Belt grinders. For example, Ive been contemplating a setup like the following: Ken Onion Work Sharp on low speeds with automated misting to keep cool, then brief time spent with whetstone sharpening to replace the very narrow section of the edge that may have still suffered some softening. Excellent article. I understand the concerns of burning the edge but as long as you are careful there isn't a problem. Not too long ago, I dropped a friend off to pick up his car at a high end auto shop. What do you think, is it possible to overheat the edge from repeated cutting if abrasive materials? Metallurgy and Testing of Knives and Steel. Thanks for the reply, Larrin. For now Im of the opinion that the pm2 was probably just underhardened, but I feel there is definetly eveidence implying that something happened in my testing that affected the steel at the edge. If you use plateau sharpening on stones (shaping both sides to the point just before they meet and form a burr and then using a few ultralight higher angle passes to form an apex) you have very good control and you don't waste any steel (a burr is an indicator that you finished shaping one side of your edge which kind of is wasted steel). Required fields are marked *. Here is an image of a high speed steel tap which is darker at the edge indicating overtempering: If the edge is greatly overheated the steel can become so hot that it can actually reach temperatures sufficient to reharden the steel, usually 1400F or above, depending on the steel in question. If I could only have one sharpener it would be a belt grinder. There is no point on discussing it. It only takes off more material if you're not paying attention. Your email address will not be published. Lowered the angle on both, the pm2 was just like any other knife while the Native was extremely time consuming. Belt grinders are fantastic. Using each knife to make the same cut in a material, will result in more friction with the dull knife than with the sharp one. I can get some pretty insane edges off of it in about 15 min start to finish. Why is this? and any of my stones costs more than those. If you previously registered for the discussion board but had not made any posts, your membership may have been purged. Allowing metal dust to accumulate in the dust collector of a surface grinder can make for a VERY interesting fire. Im thinking this might remove the over tempered steel from the grinder? Each bottle was about $300. Holding the knife with bare hands or dunking in water between passes is not likely to be sufficient since the heating occurs so quickly. 010 thick behind the edge, its on the micron or less thick edge, and think about potentially how quick that would overheat on a belt, or abrasive wheel. I haven't been here too long. And it did not dissapear and can make another hole afterwards. A quick update on this. Update 2: Roman Landes gave me some microhardness measurements of an edge after being ground with 220 grit belts. Cant really say Ive ever noticed the same heat from cutting anything else. Hand sharpening or water cooled sharpening are the best methods for preventing overheating of edges. Would strop back to hairwhittling for over two weeks. Thank you for putting this together. with the blade grinding attachment, saved my sanity. Among knife users it is somewhat less common though the Work Sharp gets some use as well as Harbor Freight 130 grinders: When grinding with a belt or a wheel hard media abrades away steel as fine particles: The steel often sparks as it is removed from the steel: You might think that the steel has to be reaching extremely high temperatures to be burning up like that as it leaves the steel. DOEHDBK10812014 Primer on Spontaneous Heating and Pyrophoricity Now imagine, if instead of it happening on a blade only . I like them for setting bevels, not so much for the finish work though they can do that too with a nice belt selection. My belt grinder has a variable speed motor, I seldom run it very fast but is still way quicker than by hand. Our auto repair shop is capable of servicing a variety of models. So I keep seeing people say don't let anyone sharpen your knives with a belt grinder. Any thought on a hybrid method? [6] https://web.archive.org/web/20160118100853/http://global-knife.com/catra/. So if you're thinking of using a belt sander as your main way of sharpening for whatever reason you have (faster, easier for you, doesn't make your arm tired etc) then there is nothing wrong with it. And the tempering times are longer than necessary generally, ie similar hardness would be reached with a 30 minute temper vs 2 tempers at 2 hours, because it reaches a steady state where much longer times are required for a significant reduction in hardness. At Autochill engineering Services we maintain a level of excellence in service delivery. There are even numbers attached to these speeds. One of these bad boys would probably do the trick https://www.tequipment.net/FLIR/T560-DFOV/Building-and-Industrial-Thermal-Imagers/. Login with username, password and session length. At the point that is being ground it would be removed, of course. As I am trying to asses and understand the same thing how to sharpen best using multiple methods, here are some comments. But I do know I can achieve a sharper edge with stones than I can with a machine and have suspected this was the reasoning. https://knifesteelnerds.com/2018/04/23/what-happens-during-tempering-of-steel/, https://www.tequipment.net/FLIR/T560-DFOV/Building-and-Industrial-Thermal-Imagers/, How to Sharpen a Machete in 5 Simple Steps - Wilderness Today, https://www.youtube.com/embed/t6SEFqNbgc0, http://knifegrinders.com.au/SET/Effect_of_felt_and_paper_wheel_on_edge_retention.pdf. overheating no longer occurs. I was working with a researcher who ordered some expensive very fine aluminum nano-particles. Secure your membership in this community by joining in the conversations.www.tormek.com. When the iron dust ignites, is it touching the knife? Knife edges are easily overheated during powered grinding due to the small volume of the edge and the friction buildup from grinding. Friction MAY be created, but it isnt required. I dont know if the infrared thermometer would have the resolution required to measure a tiny edge. In this case the steel will be untempered and brittle. People here are biased towards stones, fyi. Tormek was found to work fine all the time. Just because more information is not available does not mean that the information we do have should be dismissed. If you want quality service for your car with a more personal and friendly atmosphere, you have found it. So, if sharpening with stones leads to lower temperatures at the edge and protects the edge also, then do you think the process of sharpening an edge without a burr would be a better method of sharpening? Guys, thanks for your positive feedback! I am curious if any study has been done to show yet, that water cooled grinding does indeed fully prevent temper damage. The measurement of knife sharpness and the impact of sharpening technique on edge durability. (2016): 1-7. Especially in the current lockdown situation I have enough time to become familiar with the new belt grinder. Or they mean that only one hand sharpening on whetsones fixes all the detemepring made by the factory power grind! Or, Typically bainite is less affected by tempering than martensite. I sharpen on my 272 but I run the belt at a very slow speed. Paper does not mention neither speed of pulling nor grits used. BTW, Friction is not required to raise a burr. They wore the edges of the knives by making cuts into bamboo and measured the sharpness after 30, 60, and 90 cuts. I need to reprofile 10 of my knives (all in S30V and S35VN) and really wanted to get a WS Ken Onion to do so without murdering my hands/wrists doing it all freehand. But still the edge should be just as hot in my mind? He reports that nearly all manufactured knives have the problem, while hand sharpened knives generally do not. Seemed easier than using stones. Very mild warming can be felt only on coarse grits (220). The native was also noticably resisting sharpening way more than the pm2. But at least it doesnt throw out a lot of dust. If I want a very quick edge I shape on a coarse stone and apex on a fine stone, doesn't have that nice mirror polish people love but it'll cut and be sharp, just looks coarse. There is also a result from 1065 Cr mod which has 0.65% carbon along with 0.7Mn-0.25Cr. They do not mention knifes or steels used, judging from the picture, it is a stamped blade <55 HRc if not worse, seems not German, so likely a Chinese one (they are from .nz). The long tempering times are recommended for larger parts and for decomposing/destabilizing retained austenite. A very sharp edge can have a diameter under a micron. I can also do the same using a 2k and 5k belt sander followed by stropping on plain leather. If a knife is cutting cardboard, it gets quickly hotter than can be held in hand. I'd just rather use a more conservative method if I can. Here is a tempering curve for a simple high carbon steel, 1095: You can see that as the temperature goes up the hardness goes down. Thanks to Ken Kneringer and Nevin Ng for becoming Knife Steel Nerds Patreon supporters! Certain steels are designed to be tempered at high temperatures. Makes sense The same work done, but less friction. We have invested in all the latest specialist tools and diagnostic software that is specifically tailored for the software in your vehicle. So my conclusion from this is that either my first blade was underhardened or the cardboard test did in fact draw put the temper. Thanks dude. For me when it comes to knives using stones is a hobby. I am wondering if there is a decent way for a guy in a garage without expensive equipment to evaluate this idea. avoiding power grinding for the most part). The shoulder was just resisting my strokes forever until I finally managed to raise a small burr. Bad things would happen pretty often. I use a slow speed and fresh belts, I only sharpen 7 knives per belt. Problem solved. Iron/steel powder that is allowed to build up on flat Ive really enjoyed this blog. I like my stones too, but I'm always looking for better ways to do things. If you want nice clean, fresh oats, you must pay a fair price. J. Neilson has two great videos on the subject on youtube. I added them to the Effect on Knife Edges section. Up to a 5 Rc difference was measured, and of course even microhardness can only get so close to the apex of the edge. Perhaps they actually have collected the data privately for their own use, but Im not holding out hope that it will reach us. If the over-tempered portion of the edge is removed by the stones then it would work. However, if the tempering temperature is exceeded then softening will continue and it will travel down the hardness curve above. PS. I feel like anyone who has ground a knife very thin behind the edge.can back up these results. I had thought that I would get some belts for my belt grinder, but I think Ill only use the belt grinder prior to heat treat. So why do people get all worked up if you mention a belt grinder? If it already is frying my edges, would spraying the blade down with water from a spray bottle between each pass on the abrasive help? We provide top notch maintenance service for all types of vehicles. Tool steels. I would love to test one of my machine sharpened blades to see how it holds up. Very helpful. Page created in 0.426 seconds with 20 queries. Not sure Ive never looked into that effect before. It is clear that one can overheat a knife on a grinder. ASM international, 1998. Yes, it certanly can. A typical tempering temperature for a knife steel is 400F or so, resulting in the desired hardness such as in the range of 58-62 Rc. They were using the original Work Sharp with no adjustable speed so a full grinding speed had to be used, but did not mention that. Buy a 130 and 220 silicon carbide belts and keep the belt wet with a sponge. The Work Sharp led to better sharpness (9) than the stone sharpening that they performed (8.5), but dulled much more rapidly: The belt sharpened knife was only 6.9 after only 30 cuts on the bamboo; the stone sharpened knife was still a 7 even after 90 cuts. Whether an entire blade gets warm is not the question, it is whether the very edge does. After 60 cuts the belt sharpened knife was only a 6.5 as measured with the Anago while the stone sharpened knife was still a 7.4. They do this through additions of elements like tungsten and molybdenum that form very tiny carbides at temperatures in the 900-1100F range that increase hardness: Non-high speed steels with sufficient molybdenum or tungsten additions can also be tempered in that high temperature range. I wouldnt think so, but you can try it out and tell us what you find. Roman Landes gave me some very interesting measurements of 8660 steel (German 1.2795) which is a 0.6% carbon steel with about 0.8Mn-0.5Cr-0.2Mo-0.6Ni. However, to my way of thinking, and please correct me if I am mistaken, getting a burr requires friction, and friction is equal to heat. Great article Larrin, thanks for putting this together. For Sale: Custom & Semi Production Knives (Dealer), KnifeMaker's Market: Knives & More for Sale, Wanted: Knifemaker / Craftsman / Related Services, Busse / Swamprat / Scrapyard Knives For Sale, For Sale: Traditionals, Slipjoints, "Old Timey", International (Non-US) For Sale & Trade Forums. (thats no why i do it, im just trying to establish the initial edge quickly ). Update:Michael Drinkwine sent me another report from Global where they reported factory sharpened and waterstone sharpened knives. I have had knives to sharpen that would have taken an eternity with those. Using steels with a high temperature temper can help prevent softening if the edge remains below the tempering temperature of 1000F or so. However, in both cases a hardness drop was measured at the edge. Or have never ground a knife with a very thin geometry. Recommended reading, I mean throughout the website knifegrinders.com.au. That is on high speed. . It's all about the operator. If you are saying that wishful thinking doesnt do much to help with the best science that we currently have, then I totally agree with you. Im so torn! You can read more about how small edges are and what controls sharpness in this article. Without knowing how long (how fast) someone was grinding particular spot and the grits and the steels involved, results are useless. disturbed due to poor housekeeping practices. They wear out good knives too fast. Im new on sharpening systems and I believe IMHO after reading and reading that belt grinder stick you on power tools. You must log in or register to reply here. So if that technique does lead to lesser performance it would be a concern. Why test then, in the smallest possible grinder? Analysis of defect mechanisms in polishing of tool steels.Production Engineering5, no. It is funny how we can use High speed tool steels to make a hole in a concrete with the red hot drill bit. To test the edges they used an Anago sharpness tester which I have not previously discussed. A stone is going to take off the same material, just slower and with more time to mess up. Press question mark to learn the rest of the keyboard shortcuts, https://www.bladeforums.com/threads/measuring-the-maximum-temperature-of-an-edge-during-belt-sanding-initial-results.1357231/. So stones are the best and really the only generally applying way for me. My blades never get hot to the touch, even at the very edge, but then I obviously cannot measure the temperature at the very edge of the blade as it is in contact with the belt. I have a harbor freight unit as well! I looked into infrared thermometers but the problem is exactly as you mentionedthe area of measurement for the infrared beam is too large to accurately measure the very edge of a knife blade. Last summer, I got a Viel 1x42 belt sander and modified it with a variable speed DC motor and reversing switch. It could be very slow or even unattainable without water cooling because of how small knife edges are (microns). I think the study is limited by the choice of the Work sharp as the grinder. That being said, it definitely takes practice and its very easy to ruin a knife on if you apply too much pressure or use bad technique. https://www.youtube.com/embed/t6SEFqNbgc0 seems to have been set to private. Even some stainless steels like 154CM can be tempered in that range. The Harbor Freight 1x30 has helped, also. I also played with the speed control pots to get the speed way down, to reduce the heat but also just the speed of material removal. Light coming from all directions (i.e., a full ring light) will not highlight edge details very well -- but if the light is directional, and the direction is appropriate, details like burrs, scratches, and unsharpened regions become very visible. Then at the surface where it was rehardened it is 62 Rc, this value is lower than the original 65 Rc because it was improperly hardened. Am I doing it wrong? For a better experience, please enable JavaScript in your browser before proceeding. Straight Razors I only use stones personally but since its actually touching my face then feel and comfort is way more important than how sharp it is. Now I am confused. [1] Klocke, Fritz, Olaf Dambon, and Barbara Behrens. I vaguely remember someone using paint that changes with temperature but I dont remember how well it worked. Yes, one can. If its an expensive knife that I have an investment in then Im partial to taking my time and using stones but at the end of the day knives are tools so I treat them as such. Grinding of edges to sharpen them is relatively common for knife makers and companies. The easiest way to avoid overheated edges is to sharpen by hand, of course. Unfortunatelly, this article did not provide any knowledge for me. Thanks for all the great information, by the way. Is this a real effect? It shouldnt be, since then the surface area would be smaller and the bulk piece would be pulling away heat. We call them handle makers. [5] Mulder, Joshua, and Jonathan B. Scott. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register. They work great for all types of sharpening. In that test, the entire knife is drawn through a grid-like material so that sharpness values are found over the entire length of the edge: The Anago measures sharpness on a 10 point scale where 10 would be an infinitely sharp edge (unattainable). Would a split second at 600f actually do damage, and if so, how much? If it works, it works. http://knifegrinders.com.au/16SET.htm Then grab some popcorn and watch videos of the glorious destruction of beautiful blades and most likely how the video creator fixes them. Sadly, many will use it to claim that grinding is bad. Ive been using a 120 grit belt to put an initial edge on my blunt knives, before sharpening on ceramic whetstones. Larger damages would take time to get out or multiple sharpenings even, but it would be doable and a 400-800 grit edge is just fine as a kitchen or working knife. Roger Hamby of CATRA also tells me that in their testing of edge retention that over 75% of the knives they test suffer to some degree of edge softening due to the sharpening process. A study was conducted in 2016 [5] where they compared a knife sharpened on the Work Sharp belt sharpener with traditional sharpening on stones. I do not know that for now, and certanly not from this article. Paper wheels on a grinder were found to work well, albeit conditionally. Thanks for the heads up btw. Normally that reaction is slow but with small particles they have a very high surface area and the reaction occurs immediately in air. It would be interesting to get close up thermal footage of an edge being set by various speeds on the grinder, then perhaps a comparison with the water misting. High speed steels, in particular, are designed for operating at high temperatures without softening. I got myself a kalamazoo 1x42 not too long ago and I have to say that I can put a fantastic working edge on a knife in a minute or two. I have done it once. I have a wet/dry 142 grinder and can drip water onto it with the top guard on. This tells me that my method of hand sharpening with silicon carbide sandpaper is good. Likely only once if one is setting the new sharper angle on the knife. Your email address will not be published. When a burr forms, it's usually easy to see as a thin bright line on the edge apex -- a line which had not been there moments ago. Sharpening on a belt grinder using Tormek jigs, Re: Sharpening on a belt grinder using Tormek jigs, Look here for the TormekCalc - Advanced grinding calculator, Quote from: Jan on April 07, 2020, 03:22:01 pm, https://www.pasovebrusky.com/product/pasova-bruska-h03/---prislusenstvi-k-h03/pripravek-pro-ostreni-nozu/526, Iron sharpens iron, and one man sharpens another, QR Code --> Calcapp Knife Sharpening Calculator. To some extent steel choice can help. Haha fossilized piece of shit. Some people are just biased, or they are "elitists" who think "My way is the only correct way", when at the end of the day if the results are what you were looking for then the method doesn't fucking matter. But the reality is that I have nowhere near enough data to determine whether or not that is a good option; Id just have to go for it and trust my intuition or very low sample size testing. buy some chinesium blades to practice on. At the very least a 130, if not a 242 or 272 should have been tested as well. I suspect it will take more material off the knife, but I can't visually prove this. only reprofiling with 220 grit will warm it a bit. After tempering, if the steel is heated to some temperature below the tempering temperature, the hardness will likely not be affected unless it is held there for very long periods of time. We can not comment on what are the factories doing. The formation of iron oxide (rust) is an exothermic reaction (it generates heat). Me personally, I'm fine with having to spend more time on a stone for the control and flexibility they give me and I like to experiment with my results and edges. I would highly recommend this place to any one who wants great service, honest value, and really great people.". Do you think an infrared thermometer be effective in measuring this? If using very fine iron particles they will react in a similar manner when exposed to air even without grinding: Instead it is the heat generated by friction in the grinding process that can lead to overheated edges. Do you think after carefully reprofiling them down to 15 dps on the WSKO at low speed, that putting 17 dps microbevels on by hand would likely remove the overheated edge and give me back max edge retention?
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