And I don't understand why. :grumpy: The current offender is a Benchmade 940 in 154cm. I sharpened it and have been carrying it. It would seem like I didn't have cut very much stuff to generate a small roll. Maybe it wasn't a roll. But when I lightly dragged my finger from the shoulder to apex, on one side of the blade I would feel something near the edge that wasn't on the other side of the blade. So I would try, emphasis on try, to strop this...thing off each time it would appear. I got annoyed after the third time this happened so I took some flexcut gold on cardboard and did about 10 strokes on each side, switching bevels each time. Then I stropped on newspaper. Carried the knife yesterday and the small roll is back. Stropped it off again the morning and then cut some carpet for a scratching post for my cat. It took the apex off in a large, stiff roll. I would not think carpet would, in its self, kill an edge. The 940 did cut the carpet though, which is more than I could say for my Military that I sharpened on the Lansky.
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I am having real trouble with my edges rolling. at least I think they are rolling.
- Thread starter Squashfan
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It really sounds like a wire edge or possibly the residual effect of a pressure burr, which will leave you with a very similar problem. After following some of your posts, I am wishing I could see video or spend a half hour checking out your technique. It sounds like too much pressure or possibly the stone is glazed or a handful of other contributing factors. Am assuming the blade had been sharpened a couple times from the factory, so cooked steel along the apex not likely.
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"cooked" steel - I like that HH!
I think too that it is likely a wired edge/burr that has not been removed. I don't know much about Benchmade's heat treat etc. but I understand they do a decent job. Something is off and yes, a video/pictures/set up would be helpful.
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Whatever the cause, it sounds like there is some weakened steel at the edge, maybe extending to some depth behind the apex. Being that you've stropped it away a time or two (or three), you might be better off gently grinding the remnants of the weakened edge away with a stone (with edge perpendicular to the stone's surface), then carefully restoring the bevels to a clean apex. As mentioned, minimizing pressure is important; if it's too heavy, a new burr/wire would likely result (heavy lateral pressure bends the steel; bent steel is weakened steel, and round & round we go).
BTW, carpet's backing is brutal on knife edges. It's very 'dirty' stuff; lots of gritty, abrasive particulates in it, and maybe some fiberglass too. Doesn't surprise me if you noticed it's effects on your edge, after cutting carpet. It's sort of like heavy cardboard on steroids, in it's capacity to ruin an edge quickly.
David
BTW, carpet's backing is brutal on knife edges. It's very 'dirty' stuff; lots of gritty, abrasive particulates in it, and maybe some fiberglass too. Doesn't surprise me if you noticed it's effects on your edge, after cutting carpet. It's sort of like heavy cardboard on steroids, in it's capacity to ruin an edge quickly.
David
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How far up the knife is it deforming? Anything.past the cutting edge is a warranty issue IMO , imperfection.in.the steel or something.
Otherwise a burr or wire edge has been discussed.
Theres also the possibility that that steel with that heat treat cannot be stable at that geometry. If this is the case try a microbevel and see if it helps.
Otherwise a burr or wire edge has been discussed.
Theres also the possibility that that steel with that heat treat cannot be stable at that geometry. If this is the case try a microbevel and see if it helps.
BTW, the angle on this knife is around 20 degrees per side.
Is it possible to weaken steel by over stropping? The knife wasn't behaving this way before I stropped it this morning. This is exactly like my earlier machete that I had over sharpened with sandpaper. Also This was new, clean carpet but the backing could still have fiberglass in it.
I will be honest, I don't know how to properly apex a knife to a sharp, durable apex. There, I said it. I have no training besides what I have read on here. And no experience except that to properly apex you must generate a very small burr and then eliminate that burr. Really, I can't say that I have successfully done this just free hand. I have done made as with a microbevel made on a sharpmaker clone. But not freehand. I have come very close when freehanding but there is always a little bit of burr hanging on. Not all the way from heel to toe of the blade but in a couple of small spots. One more thing, wire edges don't behave like this failure, in my experience. A wire edge rolls over easily when cutting paper. I cut 5-6 strips of newspaper heal to toe with this knife before the carpet. Wire edge are also very small and show minimal light reflection off of the apex at the intersection of the two bevels. This burr was large, stiff and reflected a lot of light. Much more like the apex was rounded off with a side of stiff burr.
All in all, HH is right. Until I get help in the form of first hand experience or am able to put up a video, I am going in circles. I have made great leaps thanks to the advice on here. My bevels are MUCH flatter, my burrs are much smaller and my knife are sharper that they have ever been. Despite all of the things I complain about, I am still the most knowledgeable sharpener I personally know. THIS IS NOT A BOAST. I stink at sharpening. It simply speaks of how few good sharpeners there are in this world.
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Whatever damaged or weakened steel may be on the edge, I doubt stropping would've actually created it alone; it's very difficult to do that on a stropping surface that has any sort of 'give' at all. I've deliberately tried to produce a new burr when using my hard-backed strops of paper (single thickness) over wood, just to see what kind of pressure it would take; I couldn't do it, as the single thickness of paper on the wood gives enough 'cushion' to mitigate any new burr formation. More likely, a large or thick(ish) burr was left from sharpening on the stones, and possibly thinned considerably but not completely removed by stropping. The thinner burr will obviously be more noticeable when it rolls over quickly, and might leave the impression the stropping was the cause. 154CM, and it's Japanese equivalent ATS-34, can make some amazingly tenacious, thick and tough burrs that are very difficult to 'bend' back straight or break off. A thick burr like this might 'hide' as a 'sharp' edge for a bit, but then roll over after it's been thinned down a bit by stropping with compound. This is more or less how I remove burrs on steels like this anyway, more by gradually abrading them away on the strop, as opposed to trying to break them off.
There's still sometimes a possibility of weakened steel left by factory sharpening (overheating on powered grinders), which may damage the steel to some depth behind the apex. I don't know the specific history of your knife in this case, so it may not be applicable anyway. This is the situation in which I'd use a stone to grind the edge away, then re-bevel and re-sharpen it, and see if the newly-exposed steel at the edge holds up better.
Regarding carpet's backing, even when new, it's very gritty and abrasive on knife edges. I assume that's just a by-product of how it's manufactured; probably a 'dirty' process, as with the manufacture of heavy cardboard. In reading a little bit, some carpet backing is apparently made with a natural fiber called 'Jute', which is very abrasive itself, and apparently known for inducing premature wear in the machine components used in manufacturing the backing.
David
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There shouldn't be any weakend steel left from a factory shapening. This is the second shapening try for this knife. I am thinking the carpet is to blame for the crazy damage. We will mark that off for now.
I did not know that a burr could be thinned with out being stropped off. That sounds very similar to my problem. The edge will stay sharp longer than a wire edge but still have a small roll over during use. But again, it lasts longer than a wire edge.
I did not know that a burr could be thinned with out being stropped off. That sounds very similar to my problem. The edge will stay sharp longer than a wire edge but still have a small roll over during use. But again, it lasts longer than a wire edge.
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Besides 154CM or ATS-34, I've also seen similar tenacious burrs on VG-10 (Spyderco, mostly) and 420HC at lower RC (mid-high 50s). In all cases, I get rid of them by essentially 'thinning them down' until they're stripped away, on hard strops with fairly aggressive, but smallish-grit compounds. I like aluminum oxide compounds for this (usually 'white', but I'm recently finding some of the 'greys' work as well). They do it FAST. Even Simichrome polish on a strop will take care of them pretty well, though I've found it can over-polish a bit, if taken too far.
David
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Carpet backing is really tough stuff, even new. Using it as a testing media, in conjunction with my work usage, led me to revise many of my assumptions about edge finishes and selecting for the intended job. It can and will trash an edge, especially ones with broader cutting geometry.
Some wire edges can be beastly, and function nearly as well as fine cutting edge. They will not tolerate lateral stresses, but might well cut for a while if gently used.
Am getting a ton of server timeouts on this thread, here's the rest
Some of your issues might well some down to the abrasives you're working against, if the stone is glazed it will not abrade effectively and burr removal will become problematic on many steels, in most cases a microbevel will be mandatory. Trailing edge on sandpaper will likewise create a burr that in most cases will need some edge leading to completely remove. I know you are reluctant to spend any more money on stones etc, but a verified silicon carbide stone used with oil can allow you to permanently rule out pretty much any issues with loading or glazing. Properly cared for they can eliminate a burr on most steels more reliably and with less pressure than any other grinding media. If you have a scale you can set your stone on, your pressure should be under a pound, several ounces (or less) when removing the burr.
The Flexcut Gold and other compounds can do an OK job removing a burr if its very small. On a softer surface they work better but greater chance of rounding the edge, on a harder surface is a greater tendency to possibly flip the burr. I highly recommend using the paper wrapped around the stone, and swap the paper the minute it gets loaded - any loading will reduce its ability to cleanly remove the burr, especially if its a tough one.
Another thing I highly recommend for anyone that seems to have a recurring issue - go back to a coarse stone, create the new bevel, flip the burr once, and try to remove it all on the same stone. Treat the burr removal as a specific, separate operation. Break the edge down into overlapping sections and only work where needed.
You can also drag the edge across some wood, pass it on the stone, flip and repeat. At the end you can make a few passes without dragging on the wood. Wrap some plain paper around your stone and strop on that, using moderate pressure. This will either eliminate any residual burrs, or at least shine them up for easier ID. If you have to go back to the stone, do so.
I have attempted to cover burr formation and removal on all my videos, might help to check some out (I know you've already watched some, but the monologue might have slipped by).
Lastly, treat the burr creation and removal as the goal of your grinding operation, not as a by product or nuisance. Raise burr, flip once, grind off. The more times it flips and you have to chase it, the less pressure it will take for it to flip unintentionally. Reduce this tendency and it will be a lot easier to deal with. Work the edge in sections, raise burr on one side, flip, go back to the original side and eliminate with light pressure. Plan the final removal for the side of the edge you have better working skills/mechanical control. If there's small residuals after that, defeat them where they are by only working on the edge where needed.
Starting to ramble - good luck and yes, you're undoubtedly right about your skills better than 1 in 1000 or so, maybe even better than that.
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I'd guess that you have a tough wire edge, too. But you haven't said much about your sharpening method or equipment. I presume you're using a Lansky. I took it as a red flag when you said your Military could not cut carpet after you sharpened it on a Lansky. A properly sharpened Military will cut carpet with ease. So would first suspect your sharpening technique.
You might try using a Sharpie to see where your stone is hitting the edge. One possibility is that you have an uneven bevel. I had that happen with my Military BG42. I would raise a burr on one side, but the other side was too obtuse for the stone to reach the apex and remove the burr. Nothing that you mentioned trying would remove this kind of burr.
You might try using a Sharpie to see where your stone is hitting the edge. One possibility is that you have an uneven bevel. I had that happen with my Military BG42. I would raise a burr on one side, but the other side was too obtuse for the stone to reach the apex and remove the burr. Nothing that you mentioned trying would remove this kind of burr.
Bah, I had a really nice reply typed. Hit "post" and walked away. And the stupid thing didn't take.
As usual, there was a lot of really good info contributed by everyone involved. Succinctly, I think I am under working the edge. Or to be more precise, over working in the bevel grinding stage but under working when it comes to cleanup and refinement. In rough terms, I think of the apex as a two dimensional triangle. If one side and two corners, the two corners being the shoulders of the edge, were sitting on flat table, the corner not on the table would be the apex. Instead of bringing both sides up from the table/shoulder to a strong crisp point, I am creating a burr in this place and simply straighting the burr out and calling it sharp. I need to control the burr while bringing both side up to form, and I quote Bluntcut: "A sharp, durable apex."
I am going to go to sleep now. Night y'all and thanks for the help.
As usual, there was a lot of really good info contributed by everyone involved. Succinctly, I think I am under working the edge. Or to be more precise, over working in the bevel grinding stage but under working when it comes to cleanup and refinement. In rough terms, I think of the apex as a two dimensional triangle. If one side and two corners, the two corners being the shoulders of the edge, were sitting on flat table, the corner not on the table would be the apex. Instead of bringing both sides up from the table/shoulder to a strong crisp point, I am creating a burr in this place and simply straighting the burr out and calling it sharp. I need to control the burr while bringing both side up to form, and I quote Bluntcut: "A sharp, durable apex."
I am going to go to sleep now. Night y'all and thanks for the help.
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Burr removal should start with your very first stone.
Focus on abrading the burr in place without flipping it over. I find extremely light edge leading strokes help. The feedback you get when only the burr is contacting the stone is janky. It is glareingly obvious. Make 5-10 extremely light edge leading strokes on only the burr and not the rest of the bevel. When feedback smoothes out flip to the other side and repeat. Then do some.extremely light alternating edge leadi.g strokes and you will be left with a sharp sticky burr free edge.
If you can do this off your coarsest stone then everything else becomes candy. Spend your time.there.
Focus on abrading the burr in place without flipping it over. I find extremely light edge leading strokes help. The feedback you get when only the burr is contacting the stone is janky. It is glareingly obvious. Make 5-10 extremely light edge leading strokes on only the burr and not the rest of the bevel. When feedback smoothes out flip to the other side and repeat. Then do some.extremely light alternating edge leadi.g strokes and you will be left with a sharp sticky burr free edge.
If you can do this off your coarsest stone then everything else becomes candy. Spend your time.there.
I am working on a carbon steel Boker on the coarse side of the Norton India right now. I have really, really tiny burr on there. Still to much burr to have any sharpness though. I am using very light passes, almost just the weight of the blade light. Having a little bit of trouble with it but I think it is because the knife's primary grind is so poorly ground it is affecting sharpening. How poorly ground? I can see a divot in one side of the primary grind. And I think the blade may be bent too. The specific problems is one side of the blade is spontaneously producing a microbevel under which the burr is hiding. I can gently grind the microbevel off and it comes back after a couple of passes. That is not my fault. Will probably have to finish this blade on the sharpmaker.
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Another aspect to think about: simpler carbon and stainless steels abrade much more easily, therefore will grind and form burrs much more quickly. When you find yourself in a situation where you're trying to do some significant re-shaping of the bevels, but at the same time are having issues with burrs getting too big or unwieldy, a finer grit can help get that under control. What I'm getting at is, you might try the same work using the 'Fine' side of your India instead. Keep pressure light as always, but take advantage of the somewhat smaller (gentler) grit to gradually set your bevels, and keep the burrs to a more manageable size. This is generally why I've been in the habit of using Fine/EF diamond hones on simpler steels, and almost never go any coarser; they still work very fast, but the smaller grit will allow finer control over the pace and size of burr formation, AND will also make refining the edge easier. This is also helpful if you find it difficult to lighten pressure enough to minimize the burr formation; it's often easier to keep pressure at a level that's easier to control & regulate (but still light), and let the finer grit moderate how aggressively the stone is working.
In a nutshell, try to scale the grit size to the abrasion-resistance of the steel type you're grinding. Use just enough grit to get the work done efficiently, but not so much that it's difficult to tame all of the 'side effects' produced by grit that's too aggressive for the steel.
David
Good idea! I will have to experiment and see if I can get the fine side of the India to cut quickly. It is not that the India can't but a question of can I get it to. If the India won't do for heavy rebeveling, the fine side of the SiC does cut well. I have tried that before.
I was going to say, I feel better about my sharpening from this thread. The advice from the experts on here is starting to trickle down when I am at my stone.
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Take a good close look at the blade from a number of orientations - this is something you can observe Murray Carter doing before he starts on a knife. ID the warp and note its exact location. The bent/warped area can be worked from the inside curve just like a recurve (lower the handle slightly) - will be visible as a thinning of the bevel for no apparent reason, and will make it impossible to cleanly work it on the flat of the stone. It can keep a surprising stretch of the edge on either side from positively contacting the stone, so will need to be ground flat or worked in detail as described above. The opposite side might show a slight widening of the bevel at the same point, but is easier to deal with the outside of the curve, so might pass unnoticed. A large number of knives have small warps that can make trouble, especially when first sharpening.
The coarse side of the India stone has few boosters to recommend it. Frequently comes somewhat glazed from the factory due to the surface leveling. I never used mine till I lapped it good with loose silicon carbide grit, it works well now, but can still whip up a large burr if not carefully watched.
For really tough burr control I will repeat the recommendation to use a SiC stone. Due to the increased friability of the abrasive it is less prone to making larger burrs in the first place and is a lot easier to remove same. As an abrasive, SiC also tends to treat all steels very similarly, more so that AlumOx or diamonds IMHO - is a lot easier to predict how it will work and what sort of edge you'll wind up with. The India stone is a great tool, but requires a bit more finesse or added burr removal post stone work.
I kinda want to start from scratch with my questions. Answer if you want.
How old/ how long have you used these knives?
How do you sharpen them? Start to finish.
How do you maintain the edge between sharpening?
How long between sharpenings do you go?
Which did you do last?
How old/ how long have you used these knives?
How do you sharpen them? Start to finish.
How do you maintain the edge between sharpening?
How long between sharpenings do you go?
Which did you do last?
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Whole-heartedly agree; using a SiC stone is a good idea. When compared to all the AlOx variations out there (some are great, some are horrid, and many in between), I have liked SiC because it is indeed very easy to predict how it should work. The 'Fine' side of my inexpensive SiC 'Economy' stone from Norton has been very easy to get along with, and I've seldom felt the need to even use the Coarse side. :thumbup:
David