Help I can't seem to get a really good edge on this knife. Not sure if my back bevel isn't right or what. I can get it mirror polished with diamond, course, fine, ultra fine and stropping but it doesn't want to slice like a NINJA tool on newspaper. Any ideas? I am having a trouble getting a big burr, even using the diamond.
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having trouble with sharpmaker and sog twitch
- Thread starter matlocc
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What angle you try to sharpen this?
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Sent from my iPhone using Tapatalk
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The reason any edge won't cut well is because the apex isn't as crisp as it should be; either because the edge is rounded off or just not fully complete, or both. I'm betting it wasn't fully apexed before moving from the first (coarsest) step. Polishing the edge won't do any good if it's not apexed first.
Establish a newsprint-cutting edge with the coarsest stage (diamond) first. Don't move beyond that step until it can cut the paper cleanly. Diamond is very clean-cutting on steels such as this (the SOG Twitch is likely AUS-8), and you won't necessarily produce a BIG burr on it (this is an advantage with diamond). It will still show more subtle signs of burr formation, though, and it's a good idea to keep test-cutting on the paper to see how easily it's cutting (or not). Stropping can sometimes indicate the presence of a small burr, if you see bits of leather or compound collecting on one side of the apex (the side to which the burr is leaning).
BTW, I was touching up the edge on my older SOG Twitch XL (AUS-8 steel) a couple nights ago, using a Fine diamond hone (Fallkniven DC4). It'll take a screaming-sharp edge this way with minimal burring, so no worries about the diamond not being up to the task.
David
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ok, so I should go back to the diamond. (Redo the bevel or just the edge?) How do you know when you are done with the bevel? how many swipes (about)? use the edges or the flats? what am I looking for in a newsprint cut? nice slice no tearing? It is AUS-8, I can't get much of a burr at all. I have an sog seal pup I did on a chefs choice and then finished on a sharpmaker but I want to learn how to do this!
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For now, just focus on cleanly apexing the edge. I wouldn't complicate anything by trying to completely redo the bevels; at least not yet. I'd use just the flats of the rods; the bevel will be more stable on the flats, so less chance for error. Don't worry about counting passes; it's too unreliable. Instead, look for burr formation and also frequently check cutting performance with the newspaper.
For paper-cutting, the diamond-finished edge should slice aggressively through newsprint, with a 'zipper-like' feel to it. There may still be some slight snagging on portions of the edge, if burrs or small remnants of burrs are present (and they likely will be, to some extent). Look for that with some SLOW heel-to-tip slices through the paper; it'll catch or snag where the burrs are. But it should still slice the paper very aggressively and easily, if the edge is apexed off the diamond. Assuming so, some stropping afterward should quickly reduce the snagging by the burr remnants, and the aggressiveness of the paper-cutting should feel correspondingly easier as a result.
David
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Length of the blade doesn't matter. The 'aggressiveness' is in the toothy bite left on the edge by the diamond. And the pressure needed to initiate the cut depends mostly on the crispness (i.e., the width) of the apex. The cleaner and thinner the apex is, the easier it'll be to initiate the cut. If it's really crisp and thin, the apex will tend to bite immediately upon contact with the paper's edge, needing virtually no additional pressure exerted to start the cut. So, if it's cutting the paper, but you notice it takes a little more pressure to start it, chances are the apex could be made a little thinner and crisper. That's the route I always take, when noticing it's not biting as easily as I'd like.
David