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Post by bluetrain on Jul 9, 2018 13:31:01 GMT
This question mainly pertains to knives but I suppose it applies to anything with a blade.
I realize that it is commonly assumed that a carbon steel blade is easier to sharpen than stainless steel, are there knives that refuse to take a good edge (to put it one way)? Or is it more of a case of the original product as purchased having such a poor edge that achieving a really sharp cutting edge is an awful lot of work? This gets back to the question in another tread about how sharp is sharp.
I looked over my accumulation of knives, drawknives and machetes, testing them with the usual thumb on the edge. Some were really sharp, some were so-so and some were dull. I have to add at this point that the degree of apparent sharpness seems to have little bearing on which one I choose to do something in particular. When I have to cut through carpeting, I have always used a large Buck folding knife, though it isn't the sharpest knife I have. But when doing certain wood projects, the one I always use is the sharpest one I have. I use those the way they came.
But I have a couple of stainless knives, nice and handy in their own ways, that have poor edges. Achieving a good edge comparable to the others has been an effort, though I've managed to make good progress, almost to the point that I'm satisfied. But it doesn't seem like I should have needed to do that. On the other hand, keeping the two machetes I have, one a Collins, the other a Martindale, in tip top shape has been easy. They have really sharp edges, though not smooth. In all of these cases, it doesn't seem to make any difference how thick the blade is or what sort of angle the edge has. Some have just been very difficult to sharpen and so I wonder if some knives, cheap ones, presumably, cannot be sharpened decently.
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pgandy
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Post by pgandy on Jul 9, 2018 14:15:20 GMT
I don’t know the answer. I believe that all knives can be sharpened. To the degree, edge retention, and ease of sharpening will vary. I think possibly the sharpening technique will depend on the material. I grew up with carbon steel blades. Never considered myself an expert, in fact I never thought about it. I learned to use an Arkansas stone to maintain an edge on my knives sufficient to skin and other chores I had. One day I bought a Buck SS sheath knife and was so impressed I bought a second in short order, different model. Then the day came they needed sharpening, I think one chipped, something that I never experienced with carbon steel. I tried the methods that I knew and failed to get an edge. I think that I got further chipping, but not sure at this point. I told the problem to a retired marine buddy who had more time than me and he took the knives and returned with good edges, not up to factory standards but good. With the exception of my diving knife and kitchen knives they were the only SS knives I owned. I can’t remember about the diving knife but I sharpen the kitchen knives with no problem. I don’t think the diving knife ever had a keen edge but usable and since I did a variety of jobs such as open oysters I don’t think a keen edge would have lasted, but it would cut and never chipped. And since I bought a Work Sharp the kitchen knives sharpening is much faster. The type of SS I believe plays a part.
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Post by bluetrain on Jul 9, 2018 14:31:57 GMT
I'm no expert either but the real issue as I see it, is that one expects that new knives should be sharp when you buy them but some aren't. And the ones that aren't are difficult to sharpen. But some that are really sharp to begin with can be difficult to sharpen, too. Maybe it's a question of (my) skill, not to mention my patience. I have some ancient Arkansas stones but no grindstones or electrically powered aids, which is probably just as well.
It is a good excuse to go out and buy another knife--or box cutter or X-Acto knife!
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AndiTheBarvarian
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Post by AndiTheBarvarian on Jul 9, 2018 15:16:08 GMT
Afaik the ca. 13 % cromium in stainless steels makes bigger grains in the microstructure of the steel. That's the reason why carbon steel blades should be better in getting very sharp. Also high alloy stainless steel blades can have very hard edges that are more difficult to sharpen. And cheap stainless steel kitchen knives can be very soft.
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Post by Deleted on Jul 9, 2018 15:37:40 GMT
Cheap soft stainless can be really frustrating to get a decent edge. Some other steels are so hard, one really needs diamond to remove material (or a belt grinder, or wheel).
Soft blades develop a wire edge quickly when using a stone but as easily breaks off as soon as you swap sides, meaning starting over again. Then, even if finally getting a decent edge, is easily dulled and rolled.
Practicing on cheap butter knives can help learning the deft touch to not lose the edge time and again while sharpening.
An edit to include the frustrations of sharpening ceramic blades at the other end of the spectrum. Diamond plates and then paste. Or, endless patience with papers.
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pgandy
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Post by pgandy on Jul 9, 2018 16:16:46 GMT
I'm no expert either but the real issue as I see it, is that one expects that new knives should be sharp when you buy them but some aren't. And the ones that aren't are difficult to sharpen. But some that are really sharp to begin with can be difficult to sharpen, too. Maybe it's a question of (my) skill, not to mention my patience. I have some ancient Arkansas stones but no grindstones or electrically powered aids, which is probably just as well. It is a good excuse to go out and buy another knife--or box cutter or X-Acto knife! I have tried many sharpening methods and only recently have gotten the Work Sharp, which I find a jewel and plan on getting the blade grinding attachment. It is not the ultimate and I find that depending on the blade other methods may work better. When I find a blade that doesn’t sharpen to my satisfaction another method might just do it. I never gave up on the Arkansas stones but began using sandpaper more than the stone, and that became my favoured before getting the WS and I still use sandpaper method. I find the WS doesn’t get the blade any sharper only that it is faster and easier to use. Some people who lack the knack of sharpening by hand do find the WS will give a sharper edge. I find no one sharpening device will work equally as well on all blades. Those X-Acto blades will dull too with use. I just sharpened a #11 blade.
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Post by Lancelot Chan on Jul 9, 2018 16:18:14 GMT
The steel metallurgy and grain will affect how fine an edge you can form with it. The higher grit you go with the finishing, the edge apex's width will be narrower, thus sharper, finer, but weaker. A good steel will be able to take higher grit finish while a bad steel wouldn't be. The angle also makes a difference. The higher grit you go with the finishing, the larger the angle you have to do it with. Otherwise, the apex won't hold against even slicing soft stuff in its first cut.
With crappy steel, you can do with a more robust angle and a lower grit finished apex.
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Post by RufusScorpius on Jul 9, 2018 22:00:49 GMT
Speaking only from my personal experience sharpening all kinds of knives over many years, I have come to the realization that it's all about the steel.
Let me explain. I've had lots of knives, lots and lots and lots of them. Everything from high end established brand names down to truck stop nekkid lady junkers. Some took and edge, some did not. Was it my sharpening skills? No. In the early days I used a stone and thought that knives that just wouldn't sharpen were because of my lack of skills, so I bought a Lansky knife sharpening rig. Now my angles are exact, on every single blade. Same angles, same stones. Some knives get really sharp, others don't, some knives get sharp and don't hold and edge, others do. The difference is in the steel.
I also sharpen knives for my boys' cub scout group when we are out camping and I get bored. A wide variety of knives comes across my picnic table- from cheap to almost good. Same results. Some knives just won't take an edge. It's the steel, not the technique.
That is why I am now a firm believer in the church of the Get What You Pay For Steel denomination of the Don't Buy Chinese Knives religion. It's the steel. Pay for good metal and you will have a good knife. Forget about the color of the scales or the gimmick tactical junk attached to it. Steel. Nothing else makes the knife useful or sharp.
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Post by bluetrain on Jul 9, 2018 22:35:35 GMT
Good post and I agree with you. An X-Acto hobby knife or a box cutter from Home Depot are essentially disposable blades, just like the razor you probably use. And speaking of razors, it seems like you are less likely to nick yourself when a razor that's been used a few times. In other words, even a razor can be too sharp.
On the other hand, a paring knife from Wal-Mart is just about as satisfactory as one from Williams-Sonoma at eight or ten times the price, at least up to a point. But a sheath knife for outdoor use might be another story. Of course, when it comes to knives, the sky's the limit as far as price goes.
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Post by Adrian Jordan on Jul 10, 2018 0:34:54 GMT
I'm terrible with free hand sharpening so I have used one guided system or another for a while now. Currently I'm getting used to a Work Sharp. Up until that(and still sometimes) I used a DMT Aligner kit. I like it better than my Lansky kits that I've used before it, as I can get better results with it for whatever reason. So, between what I have I can gets a good sharp edge on most any knife I own. That being said, I have run into a few knives who just would not take an edge. First was an old stainless folding knife. Not sure what brand, but one of those classic Case style ones with the two blades. Another was a Schrade folder. Last one was a Kershaw Kuro my nephew found on the side of the road. That one surprised me. It is one of their Chinese manufactured blades with the 8cr13mov blades, which, while not the greatest, have been very good performers for me, and exceedingly easy to sharpen and polish. I think that it probably was just a bum blade. Even the best companies let a lemon get through every now and then, and even a marginal steel like the 8cr13mov can take a great edge if they have been heat treated well. So, in the end I think that if you've got a knife that wont take an edge and the company is reputable and the steel on the acceptable level of quality that will sustain use in its intended field then it probably just got a bad heat treatment.
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Post by Sir Thorfinn on Jul 10, 2018 16:22:13 GMT
IMO, with the right tools, you can get anything, and I mean ANYTHING sharp. Look at the dood who makes knives outta plastic, aluminum foil etc.
HOWEVER...the disclaimer here. Once upon a time, I decided to grossly overspend, and get an amazing system, the "Wicked Edge" system. Is it good, yes. Does it have limitations, yes. But what I learned is that with a controlled sharpening angle, and patience, you can get the edge stupidly fine. Fine enough that the material cannot be further refined, so a microscope is needed, but at some point, the edge can only get so thin before its micro chipping. (Adrian alluded to this)
Now...having said that, I have been given complete pieces of crap, that you can get stupid-sharp, that dull at an astounding rate.
So, IMO, it comes down to the material, what you want to use it for, and the care put into the tempering process.
I have had knives from the same company, same models, same steel... vary.
Really, I think it many times comes down to you get what you pay for. (usually) If you spend more, more care is taken in production and quality control.
And for the record, I took a strip of road sign aluminum, and made it waaaayyyy beyond razor sharp once to prove a point. Used it as a letter opener for a month, by the end of the month the back edge was as useful as the lead edge...
Just my longwinded $.02
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Post by randomnobody on Jul 10, 2018 19:08:30 GMT
I've had some of my best knives suddenly decide they don't want to be sharp anymore. For the longest time, their edge would be great. Shaving hair off my arms every time, only minor touchups once a week or so, then suddenly they wouldn't cut anything.
One of my favorite knives ever fell to this, and I'm still upset about it. I'm thinking, though, that it must've just been "case hardened" or whatever they call it now when the still is only "hard" for a few millimeters into the surface, and I must have ground beyond that in my obsession over keeping it just that sharp for five long years of hard labor.
I've also suffered the overly-fine edge problem. Grind it too thin and it'll just break off and you're back where you started. I've done this a few times.
Steel has a lot to do with it, heat treat even more, but when dealing with mass-produced stuffs, there's no guarantee one will be anything like another in that regard. Close, maybe, but wildly different is also a possibility. Good batches, bad batches, one single knife decided it just doesn't want to...
Angle is important. Grit is important. Stability and consistency are important. Any one of those off at any point and the whole thing could be scrapped. Devices with preset angles make things easier to keep consistent, but they're not the end-all and you still have to put in work, yourself, to get the most out of them. There's also the problem where the available angles may not be the best option for your specific blade. Even if it is, you may still be installing a very thin, very fragile edge.
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