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Post by bandeaurouge on Aug 13, 2024 4:55:27 GMT
My dojo pro 23 came today. Its sharp, cant shave arm hair, but it rolls through the foam packing inserts like a hot kitchen knife in room temp butter when dragged on the blade edge.
Was carefully feeling the edge and spots of it feel as if the blade was sharpened to much and the edge started rolling. At that point I had to ask this,
Many years ago I had a small interest in wood carving along with making wooden ship models. One of my knives was a high end Veritis swedish carving knife. I would always sharpen it with two grits of sand paper, the second one was actually 1,000 grit wet dry emery cloth.
The cloth would take the "roll" or burr off the edge leaving me something wickedly sharp.
Is this a smart idea to try after ive done some cutting with it?
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mrstabby
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Post by mrstabby on Aug 13, 2024 8:49:53 GMT
Personally I strop everything with leather and 2,5µm diamond compound. You can get a barely sharp edge much sharper, but if the roll is too big you need to do some grinding. I would be careful with 1000grit, it could be to low depending on how mirror the edge on the Dojo is, you might not get to the same sharpness level or a very noticeable "cloudy" spot, especially if you can't hold the angle by hand.
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Post by bandeaurouge on Aug 13, 2024 16:34:43 GMT
I was thinking more on the lines of just running it on a razor strop a few times to get it "fixed"
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mrstabby
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Post by mrstabby on Aug 13, 2024 16:53:49 GMT
If it's a strop without compound it will do little since an empty strop is just to straighten out a very fine razor edge, it can't unroll sword edges as easily or really do any sharpening. If you use compound it will depending how bad the roll is, if you can barely feel it or it's a burr from sharpening it works, but on bigger ones you need to minnimize the roll first. If it's an unsupported strop (like a belt) it could change the edge angle a bit and make a convex microbevel. It also would likely make contact with a lot of the blade annd could leave some more polished spots. I would use a strop with backing (like glued on wood) and you need compound.
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Post by larason2 on Aug 13, 2024 19:56:22 GMT
It's easier with stones, but I would try 1000 grit sand paper. Put the paper on a solid backing, wet the sandpaper, and try to apex the edge with it on either side, edge first (Japanese style), trying to approximate the angle of the very tip. That will get rid of any burr, and leave it with a toothy microburr, which is what the Japanese like. There are lots of other possible strategies though. This one only requires a single grit of sandpaper or stone. My opinion is the edge should be usable at 1000 grit. I refine it with higher grits, but 1000 should make it cutting ready. It's better to spend more time on higher grits when learning technique, as you're less likely to ruin it that way.
That being said, it will probably scratch up the finish. I never worry much about the finish on my dojo pro, since I see it as a tool for training, not a work of art. I definitely don't cut with any blades I have spent a significant time polishing. It's odd you have some rolled burrs, mine came sharp enough to cut with along the whole edge.
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mrstabby
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Post by mrstabby on Aug 13, 2024 20:47:44 GMT
Leaving a burr of any kind can make a blade feel sharp but lose sharpness quickly, I would definately try to remove all of it (depending on steel and hardness this can be some work, tougher steel means burr is harder to remove). If it's a big roll you could try to straighten the roll with a piece of hardened steel (should be harder than the edge), it might lessen how much you need to remove.
What and how you cut should determine the finish, but generally you'll do better the higher the finish, so if you can go higher, do it, but you need to keep steps, don't jump from 1000 to 5000, do a step or so in between (or use old paper). You can go from any grit to a strop and retain whatever toothyness you like and get it shaving, but for most targets high mirror just cuts better (theorethically you can make a 400grit shaving edge, I can't do those though). Only draw cuts need a toothy edge, but that's not someting you normally do. 99% of cuts go straight through with little to no sawing action. Since sandpaper gets used up it will become more polishing, a fresh 1000grit can get a toothier edge than old paper. Personally that's my problem with it, it will dull fast and change its properties, just be aware of that. I have forgotten and changed paper just to realize I meed to do the whole again since I just made an ugly spot. Its less about the grit and more about that the edge has a good apex, you need to keep good angles. A strop os meant to refine, but it depends on how damaged the edge is. Sharpness is relative, so is damage and rolls and burrs. Some people think something is edge damage, others say as long as it cuts its fine.
Oh and edge angle matters a lot how tough the edge is, and even running a strop or stone once over the edge at hogher angles can toughen the edge a lot, at the price of losing some slicing potential.
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Post by larason2 on Aug 13, 2024 21:24:00 GMT
I don't think that's totally true, probably you've read this article before: scienceofsharp.com/2024/02/03/seven-misconceptions-about-knife-burrs/When you edge lead the sharpening at very light pressure, it's very hard to avoid forming a microburr. However, the burr is pretty robust if you do it right. If you do this starting at 1000, then go up grits, say 2000, 5000, 8000, each time it will get finer, but you will still have a very fine, relatively toothy edge. This bur can be removed by increasing the angle slightly starting with about the 2000 stones, but it's perfectly usable. I have such an edge on all of my Japanese kitchen knives, and they cut well for a year or more without needing to be touched up. Such an edge will shave the hair on your hand, but it's not good enough for the face. You have to remove the micro burr somehow. Still, it's more than good enough for swords. All of the other burrs mentioned above are bad in my opinion, because they tend to be unreliable. I got a Japanese razor with a foil edge, and it wouldn't stay sharp to shave the whole face. Some insist a razor should have a bit of a foil to be sharp, but not me! So here, for a beginner, it seems to me it's hard to go wrong recommending 1000 grit with edge leading strokes at the correct angle. Stones would be better, but it's easy to get automotive sandpaper at 1000 grit. Your point about replacing sandpaper frequently is good. I only use stones for a few seconds before lapping again. I'd probably use sandpaper the same. The advice I heard is "use sandpaper as if it's free." It seems to be wasteful, but the best sanding/polishing is the first few seconds of the paper's life. After that, you're sort of wasting your time, though it will do something. You'll finish twice as fast if you don't bother trying to get life out of the paper though, the first few seconds are that much better. The same goes with Japanese sword polishing.
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mrstabby
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Post by mrstabby on Aug 14, 2024 5:26:08 GMT
I don't think that's totally true, probably you've read this article before: scienceofsharp.com/2024/02/03/seven-misconceptions-about-knife-burrs/When you edge lead the sharpening at very light pressure, it's very hard to avoid forming a microburr. However, the burr is pretty robust if you do it right. If you do this starting at 1000, then go up grits, say 2000, 5000, 8000, each time it will get finer, but you will still have a very fine, relatively toothy edge. This bur can be removed by increasing the angle slightly starting with about the 2000 stones, but it's perfectly usable. I have such an edge on all of my Japanese kitchen knives, and they cut well for a year or more without needing to be touched up. Such an edge will shave the hair on your hand, but it's not good enough for the face. You have to remove the micro burr somehow. Still, it's more than good enough for swords. All of the other burrs mentioned above are bad in my opinion, because they tend to be unreliable. I got a Japanese razor with a foil edge, and it wouldn't stay sharp to shave the whole face. Some insist a razor should have a bit of a foil to be sharp, but not me! So here, for a beginner, it seems to me it's hard to go wrong recommending 1000 grit with edge leading strokes at the correct angle. Stones would be better, but it's easy to get automotive sandpaper at 1000 grit. Your point about replacing sandpaper frequently is good. I only use stones for a few seconds before lapping again. I'd probably use sandpaper the same. The advice I heard is "use sandpaper as if it's free." It seems to be wasteful, but the best sanding/polishing is the first few seconds of the paper's life. After that, you're sort of wasting your time, though it will do something. You'll finish twice as fast if you don't bother trying to get life out of the paper though, the first few seconds are that much better. The same goes with Japanese sword polishing. What the author calls a burr here, I would call the apex, I really can't see any burr. Again a definition problem I guess.
This on the other hand is a burr, and it will fold over more quickly, feeling dull. The Author says "It can perform well unless or until subjected to lateral force in which case it will roll" which is exactly what I mean. Sideways force is pretty common in swords, nobody has a 90° angle 100% of the time when cutting (and the tardget steers the cut too) and the burr would likely fold over quickly. A sword edge annd knife edge are subjected to a bit different forces.
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Post by larason2 on Aug 15, 2024 1:00:06 GMT
Yeah, that's fair. The author technically calls multiple different blade edge phenomena "burr." The tiny bit of uneveness on the top picture is what I'm talking about with Japanese edge leading technique. It still catches the side of your finger, so it's not quite razor smooth, but it's still quite durable. If you want a very smooth razor though, you have to take that off with a slightly greater edge angle, just a few strokes with the finer stones.
I'd consider the one on the bottom more of a foil burr. anything that would fold over as you use it.
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Ramses1079
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Post by Ramses1079 on Aug 23, 2024 1:20:33 GMT
Great info everyone, thanks!!
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