Mykl Clark
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Yes they are called Ginsu
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Can some knives CANNOT be sharpened?
- Thread starter golok
- Start date
Cliff Stamp
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Crayola :
Most metals were at one time and still can make servicable tools. I had a Al knife made awhile ago, same maker. We were discussing alloys and he mentioned some of the materials he had made knives out of and pretty much in responce to my amazement at some of the alloys used, he went ahead and ground one out of an AL bar I had.
He shaped it with a file and polished it with sandpaper and brasso, it didn't take very long at all. When he finished it was easily sharp enough to cut soft foods and woods. He then destroyed it to give examples of some materials properties we were discussing (chopped into it with a 1095 machete and broke it showing notch sensitivity).
I am actually writing a review of one of those pieces now, a large bowie, very nice geometry actually. Yes it came very sharp, and will take a fine edge well, fine being relative of course, easily push shaving sharpness anyway. The cutting ability will be fairly high because of the geometry, but the edge durability it a concern, deep hollow grinds on AISI 420 is not a great recipe for high strength.
Consider this, awhile ago on one of the metal newsgroups someone was asking about blade steels to make knives out of and specifically asked about 440C. He was given a number of replies which basically said 440C is too hard to make knives out of use 440A instead. How does that perspective compare to the responce you would get here?
Yes, mild steel blades are rather soft, but its not like your teeth are 60+RC and you can easily chew up all manner of foods, and if desperate and without a knife (for some odd reason), you can easily bite through cord, take pieces out of most woods etc. . However, yes, it is obviously a far cry from 52100, or even a simple hardenable carbon steel like 1084.
They were knives for use on soft foods, especially ones that he would take into the woods with him. It was my impression that they were not long term tools, really just enjoyed making them, so having to grind another if one got to badly damaged was no big deal. He also makes swords out of mild steel as well. These were used for students who were just learning, they could get the feel and balance down without having to worry about damaging a fine blade. When the skill was high enough they would get a forged spring steel version.
-Cliff
Most metals were at one time and still can make servicable tools. I had a Al knife made awhile ago, same maker. We were discussing alloys and he mentioned some of the materials he had made knives out of and pretty much in responce to my amazement at some of the alloys used, he went ahead and ground one out of an AL bar I had.
He shaped it with a file and polished it with sandpaper and brasso, it didn't take very long at all. When he finished it was easily sharp enough to cut soft foods and woods. He then destroyed it to give examples of some materials properties we were discussing (chopped into it with a 1095 machete and broke it showing notch sensitivity).
I am actually writing a review of one of those pieces now, a large bowie, very nice geometry actually. Yes it came very sharp, and will take a fine edge well, fine being relative of course, easily push shaving sharpness anyway. The cutting ability will be fairly high because of the geometry, but the edge durability it a concern, deep hollow grinds on AISI 420 is not a great recipe for high strength.
Consider this, awhile ago on one of the metal newsgroups someone was asking about blade steels to make knives out of and specifically asked about 440C. He was given a number of replies which basically said 440C is too hard to make knives out of use 440A instead. How does that perspective compare to the responce you would get here?
Yes, mild steel blades are rather soft, but its not like your teeth are 60+RC and you can easily chew up all manner of foods, and if desperate and without a knife (for some odd reason), you can easily bite through cord, take pieces out of most woods etc. . However, yes, it is obviously a far cry from 52100, or even a simple hardenable carbon steel like 1084.
They were knives for use on soft foods, especially ones that he would take into the woods with him. It was my impression that they were not long term tools, really just enjoyed making them, so having to grind another if one got to badly damaged was no big deal. He also makes swords out of mild steel as well. These were used for students who were just learning, they could get the feel and balance down without having to worry about damaging a fine blade. When the skill was high enough they would get a forged spring steel version.
-Cliff
- Joined
- Mar 13, 2001
- Messages
- 1,157
Anyone who has done a lot of sharpening over a number of years is going to come across a blade every once in awhile that cannot be sharpened. I had someone bring me a 5/12" fixed blade last week for me to try and sharpen. This is a stainless blade that has a highly polished look to it, almost like chrome, and is extremly hard. Although it is a decent looking knife with what appears to be a stag handle, you can start out with xtra course, then go to medium and fine diamond stones and it will not take an edge. I have come across three lower end production folders over a number of years that would not take an edge also. As someone suggested in one of the posts, the magic marker or permanent markers work fine to determine proper angle and when you are getting down to the final point of developing an edge.
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- May 9, 2000
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I have never found a blade that with enough effort can not be sharpened. I have found many that did not stay sharp very long and others that took seemingly forever to sharpen, but none that I couldn't do.
Thanks Cliff, I find your posts to always be highly informative. I have gotten a great education on knives just from reading your posts. That's not to say that I have not gotten a tremendous amount of information from many others, but I always enjoy reading what you post.
Thanks Cliff, I find your posts to always be highly informative. I have gotten a great education on knives just from reading your posts. That's not to say that I have not gotten a tremendous amount of information from many others, but I always enjoy reading what you post.
Cliff Stamp
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Kwaiken :
[ceramic]
I have sharpened several ceramic knives before with similar results, looking at the edge under magnifiction it is just breaking apart, it won't hold a scratch pattern as fine as the abrasive should produce (compared to the same pattern on steel). It could be the angle or the abrasive or even the pressure used, it is obviously possible to sharpen them as they come sharp. Of course by sharp I mean shaving class, it is easy to get them to the point where they will cut rope and such, just not nearly as sharp as steel. I keep intending to pick up a cheap one to practice on.
KWM, thanks that is hopefully the goal.
-Cliff
[ceramic]
I have sharpened several ceramic knives before with similar results, looking at the edge under magnifiction it is just breaking apart, it won't hold a scratch pattern as fine as the abrasive should produce (compared to the same pattern on steel). It could be the angle or the abrasive or even the pressure used, it is obviously possible to sharpen them as they come sharp. Of course by sharp I mean shaving class, it is easy to get them to the point where they will cut rope and such, just not nearly as sharp as steel. I keep intending to pick up a cheap one to practice on.
KWM, thanks that is hopefully the goal.
-Cliff
- Joined
- Apr 27, 1999
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- 6,117
I have run across several classes of blade that offer particular challenges to sharpening--fortunately they are mostly rare these days.
The first type are ornamental knives with hard chrome plating. These days it is most common for ornamental knives to be made out of a cheap stainless, but in the past it was common to chrome plate a non-stainless. The chrome was hard and abrasion resistant and looked like hell if you scratched the blade. The underlying metal was very grainy and would get sort of ragged when honed. I would usually create my general bevel with a silicon carbide bench hone and finish the edge with a file. It took a lot of time.
Another problem class is cheap stainless. The grain size is large and sort of sets a limit on how fine the edge wants to get. The chrome content can increase the effort to hone without adding real strength to the edge. It seemed to me that as I tried to get a real fine edge my fine hone would load up and was not cutting cleanly. Using a nice sequence of coarse then medium then fine hones I could get a good edge, but it disapeared with any significant use. If I hollow-ground the blade and put a razor edge on the blade it could be dulled significantly when I tested the edge by cutting hand held paper. The most effective way to sharpen this material is to use a somewhat obtuse final bevel angle (30-degrees per side) and leave it rough. The best tool is a medium-fine diamond hone.
Another surprise class is tough abrasion resistant steels that are particularly ductile for their hardness. I have seen this happen with L6 alloy blades. In a couple instances L6 blades just didn't seem to want to get shaving sharp. I used multiple types of hones and strops. In one case I thinned the edge with a belt sander to help the process along. The blades just seemed to reach a plateau and stopped getting sharper. It is possible that the grain structure of my hunting knife (that began its life as a saw blade) is coarse, but I don't think that was the problem with my old Gerber MKII dagger. What I guessed was happening was that I was getting an edge burr due to ductility of the alloy and I needed an aggressive technique to remove it. I added a step to end of my sharpening process where I elevated the blade to 40 degrees from my nice clean extra-fine diamond hone and did a dozen alternating strokes on each side (edge-first). This was meant to take off any burr. Then I did maybe twice as many light alternating strokes at my normal 15 degrees. Then I finished with about 10 strokes per side at 19 degrees with my ceramic rods. This got me a shaving edge.
All the above being said, the most common problem is that the blades bevel is just too obtuse and you aren't really honing down to the edge. Use magic marker on the edge to be sure you are really cutting the metal that you need to.
The first type are ornamental knives with hard chrome plating. These days it is most common for ornamental knives to be made out of a cheap stainless, but in the past it was common to chrome plate a non-stainless. The chrome was hard and abrasion resistant and looked like hell if you scratched the blade. The underlying metal was very grainy and would get sort of ragged when honed. I would usually create my general bevel with a silicon carbide bench hone and finish the edge with a file. It took a lot of time.
Another problem class is cheap stainless. The grain size is large and sort of sets a limit on how fine the edge wants to get. The chrome content can increase the effort to hone without adding real strength to the edge. It seemed to me that as I tried to get a real fine edge my fine hone would load up and was not cutting cleanly. Using a nice sequence of coarse then medium then fine hones I could get a good edge, but it disapeared with any significant use. If I hollow-ground the blade and put a razor edge on the blade it could be dulled significantly when I tested the edge by cutting hand held paper. The most effective way to sharpen this material is to use a somewhat obtuse final bevel angle (30-degrees per side) and leave it rough. The best tool is a medium-fine diamond hone.
Another surprise class is tough abrasion resistant steels that are particularly ductile for their hardness. I have seen this happen with L6 alloy blades. In a couple instances L6 blades just didn't seem to want to get shaving sharp. I used multiple types of hones and strops. In one case I thinned the edge with a belt sander to help the process along. The blades just seemed to reach a plateau and stopped getting sharper. It is possible that the grain structure of my hunting knife (that began its life as a saw blade) is coarse, but I don't think that was the problem with my old Gerber MKII dagger. What I guessed was happening was that I was getting an edge burr due to ductility of the alloy and I needed an aggressive technique to remove it. I added a step to end of my sharpening process where I elevated the blade to 40 degrees from my nice clean extra-fine diamond hone and did a dozen alternating strokes on each side (edge-first). This was meant to take off any burr. Then I did maybe twice as many light alternating strokes at my normal 15 degrees. Then I finished with about 10 strokes per side at 19 degrees with my ceramic rods. This got me a shaving edge.
All the above being said, the most common problem is that the blades bevel is just too obtuse and you aren't really honing down to the edge. Use magic marker on the edge to be sure you are really cutting the metal that you need to.
- Joined
- Mar 13, 2001
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- 1,157
Jeff, you did a good job of describing the cheap stainless that is out there. This is what I was refering to in the above post. When I come across this type of metal I don't waste my time fooling with them because most of them won't hold and edge if you finally manage to get a half a** edge on it. The ones I have come across (I am talking about a 50+ year time span) have all belonged to someone else. One thing I have been seeing a lot of around here lately is the Pakistani type, cheap knives, and some of them can be worse than a challenge.