American Society for Metals, 1959. If the edge deforms that means the strength of the steel was exceeded. Tony Sculimbrene is a lawyer and gear-obsessed dad of two who believes a day spent outside is always a good day. Keep at it, as practice makes perfect. As described previously, martensite finish temperatures change for different steels and hardening temperatures, and the closer you get to martensite finish the lower the retained austenite. Knife sharpening is a fundamental piece of gear maintenance that even translates to the kitchen. A file is a good way to check hardness. 10. Lower temperatures typically mean a smaller grain size. A knife that is easier to take a “set” is not more flexible as much as it is just soft. Next, while holding the steel's grip with your non-knife hand, place the heel edge of your knife onto the steel. Many folks leave the edge much thicker, but like I said this works well for me. In tempering, the steel is heated to a much lower temperature, and it softens and becomes more ductile (pliable). The quenching medium I used was old motor oil. As long as we work to understand the mechanisms at work and to learn from reliable experiments rather than anecdotal observations we can continue to kill more myths. When the edge deforms (instead of chipping) that means the steel is tougher than one that chips. Light a propane blow torch to use as a heat source. This article provides some insights and workarounds for one of the most vexing problems you will encounter when sharpening a knife — wire edges. This technique is very dangerous for novices, but glass is exceptionally hard and will definitely kill the wire edge. But one mistake people make is thinking that if a little of something is good then more of it must be better and started adding in intermediate steps. Wire edges can be frustrating, especially for folks new to sharpening their own knives. There you have it. But even in those situations the recommended heat treatment would work fine. Using a Coffee Mug for Quick Results Place an old coffee mug upside down so that the bottom of … Finishing the Knife. Some steel-heat treatment combinations can even be relatively soft (rolling when performing flexing cuts in hard materials) but still have relatively poor toughness leading to chipping when chopping. 11. More fun - a smooth edge without bends or chips, which is … However, grain growth is controlled by both time and temperature. When the edge deforms (instead of chipping) that means the steel is tougher than one that chips. Annealed steel is made up of magnetic ferrite and hardened steel is made up of magnetic martensite. Yet higher hardening temperatures can be used in combination with liquid nitrogen up to a hardness of about 64 Rc. Manufacturer of Hardened and Ground Knife Edge Straight - Krystal Try Square Edge Straight, Krystal Hardened Ground Knife Edge Straight, Krystal Ground Steel Edge Straight offered by A To Z Magnetic Inspection Assebmbling And Equipments, Pune, Maharashtra. Most of good heat treating is about avoiding many of the potential issues or mistakes and not about finding the great secret. ), it is hard to say how much hardness is lost. We asked five pros how they made it work and what it takes to make a living in the outdoor industry "in real life.". From here, the trail slowly descends as the ridge bends around the basin. Then take a sharp file for metal working and sharpen an edge on it not to thin of an edge and not to thick of an edge. A wire edge, also called a burr, is the result of sharpening a knife. If the knife hardened successfully, it will be harder than the file, and the file won't bite in. 9. XXXX steel “needs” or “doesn’t need” cryo. The steel becomes nonmagnetic at the Curie point. You would need to grind all color left from heating out of the finished knife to be sure that the knife will retain its edge as long as possible. Sometimes edge deformation/rolling is misinterpreted as chipping and the knife user incorrectly believes that the steel has insufficient toughness when in actuality insufficient hardness is the issue. Some of these claims are even found in peer-reviewed journals. Some knife users or makers report happily that their knife edge rolled in use as evidence of its good toughness, but it is mostly evidence that the steel wasn’t hard enough and/or the edge geometry wasn’t robust enough. Of course, Wicked Edge/Edge Pro sharpeners are frequently used by knife aficionados to put really sick mirror edges on their customs, so keep them in mind if you’re looking for something like that. Imagine a sharpened knife edge zoomed way in. NordicTrack wants to give you $7,500 toward your dream adventure. This is why those very thin fillet knives are so good at flexing 90°. And with the social distancing required because of COVID-19, now’s a perfect time to really learn how to sharpen a knife. The quilts just don't look right to my eye - the binding immediately marks them out as not British. You can see a wire edge with your naked eye, but if you don’t know what to look for, that’s not helpful. There are other dangers to using short hold times, such as the heat treatment being much more sensitive to small changes at short times. For understanding those aspects better I recommend clicking on a few of the links in this article to better understand topics like annealing (Part 1 and Part 2), austenitizing (Part 1, Part 2, and Part 3), quenching, and tempering. Of course, focusing on any one of these factors at the expense of the others: steel selection, heat treatment, and edge geometry, is a mistake and each should be optimized for the given knife. The light will only reflect off of flat spots or rounded spots on the blade. The better a knife retains its edge, the harder it is to sharpen. The result is that the knife feels sharp but doesn’t cut like a sharp knife. Clay or another material is used for insulation. The Curie point is where the ferrite phase becomes nonmagnetic. There are two primary ways that a steel can become nonmagnetic: 1) transforming to the “austenite” phase, or 2) by reaching the Curie point. And as mentioned in the previous myth, superior edge geometry is often what makes a legendary knifemaker have high performance knives, but the super heat treatment is a better story. Put two things in the fire. The end of winter is a good excuse to do some gear maintenance. Is the grain refinement step around aus temp not usually associated with a quench to set up martensite that is faster to dissolve again so less time is used for the actual sub critical anneal step? Make sure you get out of the quench and straight into the cold treatment no matter what steel and heat treatment is being used. If you don’t have a strop, a belt can work. No heat treatment is capable of making high carbide CPM 15V into a high toughness steel. This long piece of steel is so you can bring up the temperature of your quenching oil. If you can’t prevent the creation of a wire edge by systematically counting strokes or passes and keeping your grind angle consistent, then you need to sharpen with a plan to address the wire edge after it comes into existence. 4. However, there is a whole industry of cryo companies advertising incredible improvements in wear resistance from cryogenic processing. Wicked Edge/Edge Pro style systems are much more finicky, since they have so many more adjustments and parts. Enter before February 8th for your chance to win. 6. Enter your email address to subscribe to this blog and receive notifications of new posts by email. Japanese knives are often made from high-quality but harder … A freezer doesn’t do anything; at least dry ice temperatures are necessary for cold treatments. The file works with a similar principle to the Mohs hardness scale, if one material can cut another then it is harder. The Mount Katahdin Knife Edge trail begins right near the summit cairn. There are a lot of heat treating myths out there and I haven’t covered all of them. You have the two sides of the blade coming together at a point, and riding along that point for the entire length of the blade is a small, toothy section of very thin steel raised up from the main edge. Below shows the retained austenite for different cold treatments after different delay times at room temperatures. I think enough stabilization of retained austenite may lead theoretically to great improvement in some low toughness steels . 13. For one, it isn’t very precise. However, it has become somewhat fashionable to talk about knife performance as entirely (or almost entirely) controlled by the knifemaker’s skill in heat treatment. Those formation temperatures are controlled by the steel composition and also the heat treatment, as higher hardening temperatures put more carbon and alloy “in solution” to affect the martensite formation. Here, we discuss the wire edge, or burr, created while knife sharpening and how to address it. Low Alloy and Low Technology Heat Treating Myths. It’s incredibly hard for a manufacturer to get it right and even harder to prime up the edge, but once done correctly, this knife is staying exactly as it is for a ton of time and loads of abuse. Cryo is not an on/off thing, and the colder you go the better for minimizing retained austenite. High alloy steels, on the other hand, can usually be austenitized over a rather wide range of temperatures because the carbides dissolve over a wider temperature range, this means that hardness changes more slowly with temperature changes, and the higher carbide content also means that grain growth is slower. However, there are still issues with using a file. Once the strength of the steel is exceeded the knife will keep bending with approximately the same level of force. I wrote about what is possible in heat treating and what isn’t in this article. Required fields are marked *. When using a furnace with a PID and controlled temperatures, high alloy steels are usually “easier” to heat treat. If quenching is done in a bath, quench the thick sections first, the cylindrical pieces straight up, and the flat pieces on edge. You may unsubscribe at any time. The correct time to temper steel for a knife is after the blade has been formed and shaped but before the final assembly and polishing. So here are some photos of how to make the knife edge - not difficult, but very neat looking - and- no extra fabric is needed. Myths about End Properties after Heat Treating. When it comes to maintaining a sharp edge, it all starts with the blade you've bought. The ASM Heat Treater’s Guide recommends 1525°F for 5160, meaning overheating by only 25°F can lead to a significant drop in properties! [1] X Research source Larger flames produce less heat while smaller flames produce a higher heat. – second modification : instead of double or triple tempering why not just tempering steel at secondary hardening range for 4 hours for example then following it by tempering at low temperatures “200-400°F” to stabilize retained austenite & temper any fresh martensite ? I reviewed the literature in this article. A few strokes on a strop (counting strokes and alternating sides) with different compounds will rid you of a wire edge. Normalizing needs to be performed from relatively high temperatures, depending on the steel, such as 1550-1650°F for 1095 steel. Heat Treating is the most important factor for high performance knives. Now it is time to finish off this knife! Above that temperature the hardness drops because of excess retained austenite, usually amounts greater than 15-20%, which is undesirable. In that way, this is not a myth. Safer - a recreated tip is much safer than a broken-off tip. high on Rockwell C scale) edges are brittle and softer edges are, well softer, but tougher, in that they take less damage and are somewhat more durable, overall at least. The King of Do-All Knives Is Half Price (and Other Amazing Knife Deals). With typical cutting, there is often some combination needed of hardness (strength to resist rolling) and ductility/toughness (resistance to fracture). 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