I love sharp knifes. The sharper the better. My two sharpest knives are my BM 550 and WH Evolution Wharcliffe. The WH came sharp and I made the 550 sharp. Do I have any special skills sharpening? No. I use the sharpmaker and an old belt to strop when done. My knowledge of how sharp a knife can be can be accredited to four things: (add or correct if I'm wrong) 1. type of steel used on blade 2. heat treat 3. primary grind 4. edge grind. But I don't think I really understand the dynamics of a truly sharp edge and what it takes to get one. For example, the BM 550 uses a flat grind and a thin edge and 440C steel. The MT LCC that I used to have also had a flat grind and a thin edge and used 154cm. I could get the edge sharp on the LCC but not as sharp as my BM 550. So, at one point, I sent my LCC back to MT and they sent it back with a screaming sharp edge which was as sharp as my BM 550. So I started thinking my sharpening technique must be in error, BUT how did my 550 turn out so sharp. Ok then, 440C must just take a better edge. But I just said that MT put a great edge on the LCC And what about BG42, the cousin of 154 cm with vanadium added for the purpose of limiting the size of the carbides and thus allowing for a finer=sharper edge. The addition of vanadium to VG-10, which I believe is the cousin to 440C, had the desired results because man is that steel sharp. But then I go back to the fact I can get the Sebby sharp but not as sharp ast the 550. So what I have learned so far about edges in my 3 plus years of buying knives is that: 1. the thinner the edge the sharper 2. I can't get 154cm as sharp as 440C . I can't get my Sebby as sharp as my 550 and it frustrates me because I want my Sebby to be THE sharpest knife I have and it isn't. So what is the point of this misc rambling? I don't know. But I sure wish I haven't become so obsessive about edge sharpness.
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How sharp is enough?
- Thread starter kutch133
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Kutch,
The question isn't how sharp, I can get a piece of mild steel as sharp as any one of your blades. The questions are will it stay that way in use?, and will it do the job intended? I've been using edged tools everyday for years. The angle of the grind is a function of; how it's used, and what you are cutting.
example
a block plane with blade ground at 20 degrees is perfect for pine, but will not last long when used on white oak, and the things it will do to curly maple are horrable. If you increase the angle 10 degrees, It is much better suited to oak but will bind just a little in pine, however it still will tear up currly maple. now increase the angle to 45 degrees It will act like it is dull, and will not gut pine. It will take a fine cut on either curly maple or oak but it is 10 times less likely to to dammage to the figured wood.
the blade at 45 degrees will not shave, it won't cut pine, so it's not sharp, or is it.
just somthing to think about
The question isn't how sharp, I can get a piece of mild steel as sharp as any one of your blades. The questions are will it stay that way in use?, and will it do the job intended? I've been using edged tools everyday for years. The angle of the grind is a function of; how it's used, and what you are cutting.
example
a block plane with blade ground at 20 degrees is perfect for pine, but will not last long when used on white oak, and the things it will do to curly maple are horrable. If you increase the angle 10 degrees, It is much better suited to oak but will bind just a little in pine, however it still will tear up currly maple. now increase the angle to 45 degrees It will act like it is dull, and will not gut pine. It will take a fine cut on either curly maple or oak but it is 10 times less likely to to dammage to the figured wood.
the blade at 45 degrees will not shave, it won't cut pine, so it's not sharp, or is it.
just somthing to think about
Gollnick
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At the very top of this screen, there is a blue bar. In the middle of that bar is a link to "Tutorials/Faqs". Near the bottom of the screen that that link takes you to is a link to the bladeforums.com sharpening FAQ. It really is a "must read."
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To get the Sebenza as sharp as it was out of the box, you have to put a 'convex' edge on it.
Your other observations simply show the movement of the burr in my opinion as well as the simple fact that some steels are just hard to sharpen. I can get a shaving edge on 8a with no problems, to get the same or near edge on CPM440V takes a lot of work. Some steels are not best suited to razor razor sharp edges and apart from that don't 'feel' razor sharp and yet cut like a bugger!
If the edge is good and shows no dull spots or a wire edge... And it works for the task required.
Why worry? I was obsessed with using my Ultra Fine Spyderco benchstone to get that mirror polished edge, only it works well on some steels and not so on others. The strop method you use can do more harm than good, easily rounding of the edge.
A lot of points and a lot of questions to answer! Sorry
Your other observations simply show the movement of the burr in my opinion as well as the simple fact that some steels are just hard to sharpen. I can get a shaving edge on 8a with no problems, to get the same or near edge on CPM440V takes a lot of work. Some steels are not best suited to razor razor sharp edges and apart from that don't 'feel' razor sharp and yet cut like a bugger!
If the edge is good and shows no dull spots or a wire edge... And it works for the task required.
Why worry? I was obsessed with using my Ultra Fine Spyderco benchstone to get that mirror polished edge, only it works well on some steels and not so on others. The strop method you use can do more harm than good, easily rounding of the edge.
A lot of points and a lot of questions to answer! Sorry
Cliff Stamp
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In regards to comparing sharpness of varous blades it is critical to realize what it is that you are actually seeing. Sharpness (edge aligment and polish) is independent of edge geometry, the cutting ability however isn't. Thus determining sharpness by cutting something can be misleading as a change in geometry can allow a blade that is blunter but with a thinner geometry to cut better and thus appear sharper than a blade with a more obtuse grind but a much better edge alignment and polish.
For example I have an ATS-34 blade that has an edge sharpened at about 8-9 degrees. Because the bevel is so acute, even if I do a sloppy job sharpening the edge still cuts exceptionally well. On any cutting test it will score very high, outperforming other blades I have with more obtuse edge grinds even if I am really careful and do an optimal job when sharpening them.
Specific to the high alloy steels, especially the high carbide ones, it is critical to sharpen them using a hone that can easily cut the carbides. If this is not done you will round the carbides and thus lower the cutting ability even if you do an excellent job and produce a well aligned and finished edge. I use diamond hones and SiC sandpaper (15 and 5 Micron) on all my high % hard carbide blades. I finish with a few passes on a strop loaded with CrO if I want a very fine polish. But extended stropping will dull the edge due to carbide rounding on such steels.
One thing you might want to check is that the blades that you can sharpen well are not simply sharpened at angles that you can easily match out of habit. If this is the case the blades that you can't get quite as sharp may be just sharpened at an angle that is a little too obtuse or acute for you to sharpen well freehand. If you are using some kind of jig to control the angle of the stroke then this obviously isn't a factor.
The General :
Specific to the Sebenza it comes with a convex edge, but more importantly the convex curvature is very light and thus the edge is very actute. If you want to keep the cutting ability similar to the NIB ability you can just use a flat bevel which hits the full edge width. This will take a little time to apply as you will be removing the middle of the convex bevel, but once it is done subsequent sharpenings will be *much* faster. This bevel will also outcut the NIB bevel and thus will appear sharper at the same quality of edge finish.
-Cliff
For example I have an ATS-34 blade that has an edge sharpened at about 8-9 degrees. Because the bevel is so acute, even if I do a sloppy job sharpening the edge still cuts exceptionally well. On any cutting test it will score very high, outperforming other blades I have with more obtuse edge grinds even if I am really careful and do an optimal job when sharpening them.
Specific to the high alloy steels, especially the high carbide ones, it is critical to sharpen them using a hone that can easily cut the carbides. If this is not done you will round the carbides and thus lower the cutting ability even if you do an excellent job and produce a well aligned and finished edge. I use diamond hones and SiC sandpaper (15 and 5 Micron) on all my high % hard carbide blades. I finish with a few passes on a strop loaded with CrO if I want a very fine polish. But extended stropping will dull the edge due to carbide rounding on such steels.
One thing you might want to check is that the blades that you can sharpen well are not simply sharpened at angles that you can easily match out of habit. If this is the case the blades that you can't get quite as sharp may be just sharpened at an angle that is a little too obtuse or acute for you to sharpen well freehand. If you are using some kind of jig to control the angle of the stroke then this obviously isn't a factor.
The General :
Specific to the Sebenza it comes with a convex edge, but more importantly the convex curvature is very light and thus the edge is very actute. If you want to keep the cutting ability similar to the NIB ability you can just use a flat bevel which hits the full edge width. This will take a little time to apply as you will be removing the middle of the convex bevel, but once it is done subsequent sharpenings will be *much* faster. This bevel will also outcut the NIB bevel and thus will appear sharper at the same quality of edge finish.
-Cliff
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That is a very interesting comment Cliff, what you are saying then is as the 'convex' edge is so slight on the Sebenza a flat edge of what? 20 degree's or so will effectivly cut the middle 'bulge' of the convex edge away and leave an edge that is just as sharp if not more so?
Very intersting point. At the moment I use a leather belt loaded with Chrome polish to 'slack belt' sharpen using a strop method and it works a treat with my VG-10 Moran fixed blade and my large Doug Mondt Custom in CPM 10V at Rc-58 by Paul Bos. Needless to say, if I let the edges go long enough without an edge 'fix' this would not be practical and I would need to use the Sharpmaker et al to fix it first.
Do you think for super high level Vanadium blades, that the ceramic stones are not really the best thing to use? Perhaps my DMT stones are preferable? Will Chrome polish cut the Vanadium carbides?
Thanks.
Very intersting point. At the moment I use a leather belt loaded with Chrome polish to 'slack belt' sharpen using a strop method and it works a treat with my VG-10 Moran fixed blade and my large Doug Mondt Custom in CPM 10V at Rc-58 by Paul Bos. Needless to say, if I let the edges go long enough without an edge 'fix' this would not be practical and I would need to use the Sharpmaker et al to fix it first.
Do you think for super high level Vanadium blades, that the ceramic stones are not really the best thing to use? Perhaps my DMT stones are preferable? Will Chrome polish cut the Vanadium carbides?
Thanks.
Cliff Stamp
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The General :
Yes, except the angle is much too obtuse. Spyderco sets it bevels at about 15, and Reeves is more acute still. I would assume you are in the region of say 12 +/- 2 degrees based on the Project I used some time ago, the edges are indeed very acute which is why they cut so well. Note you are losing edge durability by doing this, however the Sebenzas are high performance cutters anyway.
I found this out quite some time ago when I noticed that over time my blades were losing aggression when touched up on fine ceramics. I discussed it with Phil Wilson who commented on the carbide issue for fine polishes. For rough work, you shear away so much steel that you get fresh carbides that way, plus at rough finishes the nature of the micro-serrations due to the grit finish controls the cut and the carbides do pretty much nothing anyway.
Easily, the 1200 DMT followed by a light stropping (a few strokes) leaves a blade with an edge that is very aggressive on the slice and yet still has a high push cutting ability. The new 2000 grit version should be interesting if you want a higher polish.
No it won't even come close. The Cr oxide is actually Cr2O3 as I recall which is not much harder than steel. Most of the Chrome buffing compounds also contain fine AO abrasives as well, but these are not hard enough either.
-Cliff
Yes, except the angle is much too obtuse. Spyderco sets it bevels at about 15, and Reeves is more acute still. I would assume you are in the region of say 12 +/- 2 degrees based on the Project I used some time ago, the edges are indeed very acute which is why they cut so well. Note you are losing edge durability by doing this, however the Sebenzas are high performance cutters anyway.
I found this out quite some time ago when I noticed that over time my blades were losing aggression when touched up on fine ceramics. I discussed it with Phil Wilson who commented on the carbide issue for fine polishes. For rough work, you shear away so much steel that you get fresh carbides that way, plus at rough finishes the nature of the micro-serrations due to the grit finish controls the cut and the carbides do pretty much nothing anyway.
Easily, the 1200 DMT followed by a light stropping (a few strokes) leaves a blade with an edge that is very aggressive on the slice and yet still has a high push cutting ability. The new 2000 grit version should be interesting if you want a higher polish.
No it won't even come close. The Cr oxide is actually Cr2O3 as I recall which is not much harder than steel. Most of the Chrome buffing compounds also contain fine AO abrasives as well, but these are not hard enough either.
-Cliff
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Thanks Cliff!
So I need to use the 15 degree angle to get the Sebi as close as possible to the actual edge? I had no idea it was at such an acute angle! Now I can understand why it is so sharp.
I will keep a close eye out for the 2000 grit DMT stone. I have two of the pocket stones and the Duostone with Course and Fine. I think the Fine is 600-800.
So I need to use the 15 degree angle to get the Sebi as close as possible to the actual edge? I had no idea it was at such an acute angle! Now I can understand why it is so sharp.
I will keep a close eye out for the 2000 grit DMT stone. I have two of the pocket stones and the Duostone with Course and Fine. I think the Fine is 600-800.
Cliff Stamp
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Yes, the 15 degree bevel on the Sharpmaker will hit the actual edge if the Reeves blades I have seen are standard, and based on what I have read it seems so. A quick check with a marker will reveal the situation in any case.
Note any bevel more obtuse than the existing bevel will indeed hit the edge, it will to be specific put an additional secondary bevel along the edge. The closer you get to the NIB profile the more of the NIB edge you will hit when you apply your bevel. The same principle applies if you go too acute just in the opposite manner.
Yes the fine stone, which is red, is 600 grit, the new 2000 one is yellow. The 1200 one is green, the black one x-coarse and the blue one coarse. The grit numbers are pretty much meaningless as the various companies just seem to make them up. They don't corrospond well to any kind of standard micron size in respect to abrasive size or scratch depth.
Note, even for the same company they proceed in a strongly nonlinear manner. For example an 8000 grit japanese waterstone isn't 8 times as fine as a 1000 grit one, it is more like 20
-Cliff
Note any bevel more obtuse than the existing bevel will indeed hit the edge, it will to be specific put an additional secondary bevel along the edge. The closer you get to the NIB profile the more of the NIB edge you will hit when you apply your bevel. The same principle applies if you go too acute just in the opposite manner.
Yes the fine stone, which is red, is 600 grit, the new 2000 one is yellow. The 1200 one is green, the black one x-coarse and the blue one coarse. The grit numbers are pretty much meaningless as the various companies just seem to make them up. They don't corrospond well to any kind of standard micron size in respect to abrasive size or scratch depth.
Note, even for the same company they proceed in a strongly nonlinear manner. For example an 8000 grit japanese waterstone isn't 8 times as fine as a 1000 grit one, it is more like 20
-Cliff