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Sharpness levels defined
- Thread starter zyhano
- Start date
Well... ya clean it on the slave's toga, silly! That's why we let 'em wear the damn things in the first place!
But I've been giving it some more thought. Obviously cutting through arms is different than cutting through legs. And the legs of mine slaves are going to be thicker than the legs of house slaves... We need to standardize the slaves too.
Might as well just stick with thread...
Stitchawl
But I've been giving it some more thought. Obviously cutting through arms is different than cutting through legs. And the legs of mine slaves are going to be thicker than the legs of house slaves... We need to standardize the slaves too.
Might as well just stick with thread...
Stitchawl
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- Apr 14, 2007
- Messages
- 2,738
Zyhano, 'scary sharp' is a technique for sharpening, not a degree of sharpness. It was started by the wood carvers who use sandpaper on glass to sharpen their gauges and knives. "Scary Sharp" is the name of this system, not the results. The term became corrupted here in BladeForums to mean really ridiculously sharp results!
Disagree, no corruption involved...Knifenut1013 had gotten my knife so sharp I've been scared to touch it.
- Joined
- Nov 24, 2005
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- 10,038
Disagree, no corruption involved...Knifenut1013 had gotten my knife so sharp I've been scared to touch it.
C'mon! You're can't mean that you're really afraid to touch the blade?
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- Apr 14, 2007
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- 2,738
Yes I CAN mean....the blade only touches something I intend to cut.
An interesting video I saw was on the Edge Pro website.
http://www.edgeproinc.com/sharpeningtips.html
Watch #8. It talks about the difference between a knife that is sharp and a knife that cuts well. They are not always one and the same.
http://www.edgeproinc.com/sharpeningtips.html
Watch #8. It talks about the difference between a knife that is sharp and a knife that cuts well. They are not always one and the same.
I like this product, but it really only tests edge continuity not actual sharpness. Unless I'm missing something, there is no gauge or anything of that sort.
On a side note, I just tried it on a Bic pen, and i really could feel the two small nicks I have in my Spyderco Military.
No they are not, but it doesn't mean that a sharp knife isn't sharp. Perhaps a better way to word it would be that a sharp edge cannot make up for an improper blade grind (for the application).
I was thinking about the threadcutting, and came to the conclusion that there is really only a narrow range of sharpness where its results would be expected to be somewhat linear, maybe 1-3 oz. Beyond that, many variables would start stacking really quickly, I think.
On the other hand, knifenut's experience shows a hanging hair test to work well for a certain range of sharpness. I would expect that to actually be less than 1 oz on thread cutting.
If one was thread cutting, at 5 oz or so, there may be another test, like rope cutting, that could be a better way to remove some variables.
I am not suggesting anything in particular, just realizing why manufacturers work with CATRA and leave it at that.
Maybe hair whittling, shaving sharp, and treetopping are just fine the way they are.
zyhano
Gold Member
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- Dec 3, 2009
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- 1,593
Can you define those pleaseMaybe hair whittling, shaving sharp, and treetopping are just fine the way they are.
?Maybe hair whittling, shaving sharp, and treetopping are just fine the way they are.
'Hair whittling' is carving a single strand of hair into a scale model of the Eiffel Tower, including the elevator. 'Shaving Sharp' speaks for itself. "Tree Topping' is going out to your local forest, and with a single stroke, slicing off everything from the fourth limb up, leaving a landing strip like swath on the top of the trees. Similar to military 'high and tight but sideways.'
While these are effective tests, that last one, the 'tree topping' will really depend upon the species of trees. Obviously it will be harder to tree top rock maple than something like pine. Forget about ebony!
Hope this clears things up for ya!!
Stitchawl
Can you define those please
'Hair whittling' is carving a single strand of hair into a scale model of the Eiffel Tower, including the elevator. 'Shaving Sharp' speaks for itself. "Tree Topping' is going out to your local forest, and with a single stroke, slicing off everything from the fourth limb up, leaving a landing strip like swath on the top of the trees. Similar to military 'high and tight but sideways.'
While these are effective tests, that last one, the 'tree topping' will really depend upon the species of trees. Obviously it will be harder to tree top rock maple than something like pine. Forget about ebony!
Hope this clears things up for ya!!
Stitchawl
Is that all that $10 gizmo is? A polymer rod to act like the barrel of a bic pen so you can determine at what point the edge snags and bites in?
There are several different tests that can be run using the tester that, because of shape, won't work on a pen barrel. I've been using mine for years and appreciate the information I can get from it. I can't get that same information from pens. If I could, I'd be happy to have saved the $10. Of course, having used it so long, it really averages out to about 75 cents per year, which I'm happy to report I can now afford... :thumbup:
Stitchawl
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- Nov 24, 2005
- Messages
- 10,038
The eariler link didn't realyy say anything. What exactly can you glean from this instrument and how do you use it. If you have time to answer, no big deal though, it works for you and that's good but I still don't know what it's all about.
The eariler link didn't realyy say anything. What exactly can you glean from this instrument and how do you use it. If you have time to answer, no big deal though, it works for you and that's good but I still don't know what it's all about.
Time is never a problem for a busy man.
I use it to check the consistency of my edges as well as the degree of sharpness, but it's testing that consistency from choil to tip that this tool really does its stuff for me. I use it when I want absolute perfection in an edge. The EdgePro gives it to me, but sometimes, depending upon the steel, I don't spend enough time working on the heel or perhaps the point to really do it properly. This tester lets me know instantly.
The tests I run when using this:
1. consistency of edge; by drawing the edge along the barrel of the tester, you can instantly 'feel' even the slightest imperfections. This is the same sort of feel that you get when you draw an edge over a fingernail except that a) you don't wind up with chopped up fingernails, b) you can use a more delicate touch, and c) by drawing the tester over the blade rather than the blade over the tester, a much more accurate result.
2. degree of edge; This is one that really gives important result. The more acute the angle able to be held, and at the exact degree for the entire length of the blade, it makes a very good tester for free hand sharpening. It's not so needed for good clamp systems that maintain a consistent angle through out the sharpening process.
3. Three different testing areas; two angled and one straight. The three different testing positions allow six different tests to be run on the edges, rather than just one or two that string or shaving provide.
Many of these tests can by performed using a plastic pen or a fingernail. Fingernails do get rather chopped up by them if you are sharpening several knives. A Bic pen does work to the 'straight barrel' tests, but ONLY the straight barrel tests.
For my cost of 75 cents a year, I prefer the tester and push-cutting tissue paper. Knifeknut1013 prefers whittling hair. AnyCal like cutting thread. Everybody has their own preferences.
Stitchawl
Is that all that $10 gizmo is? A polymer rod to act like the barrel of a bic pen so you can determine at what point the edge snags and bites in?
Yep! That's 'just about' all it is. Except that it also has two angled areas as well as the straight barrel. Sometimes the simplest tool works the best. But in this case, it's that 'just about' part that makes the difference!
Stitchawl
http://www.razoredgesystems.com/images/pdf/res_guide_instructions.pdf
These are the instructions to the EdgeTester. I've also been using one for quite a while; it really saves on paper costs when it comes to sharpening knife for someone else, and you can find imperfections or deformations with the edge of it better than you can with a Bic pen--and yes I've tested.
The problem I have with the EdgeTester is two-fold. One is that, it's a very subjective tool. Then again most methods of doing this are, but on the one hand the instructions recommend using "a new razor blade" as a benchmark, and the user then has to feel or "bumps". Well, what if it's been a while since they tested on a new razor, or what if their own edges feel smoother than a new razor?
Instead of an Edge "Tester" I see it as an indicator since it's more useful for finding things that are wrong than gauging sharpness, because as far as the EdgeTester goes, blades that have gotten a full 100 point score won't shave or cut up phone book paper.
It's still a really useful tool to have for finding deformations and imperfections, and as far as "rating" edges go... If instead of a 45 degree angle, you hold the edge tester at a much more acute angle, you can sometimes get a good indication that one edge is much sharper than the other like this. So it's also pretty darn flexible.
Anyway, enough about that... I've been wrestling with this topic of discussion for a while.
"Hair popping" is one in particular I find interesting, because I don't see "hair popping" being the same as "hair shaving". As I've said before, if the hair "pops off" and has to land somewhere, then potential energy was put on it by the drag of the edge, and once it makes its way through the potential energy is released. On the other hand, hair shaving glides through the hair with no pull or friction, and leaves the hairs laying in a neat pile. I can get "hair popping" off of a 220 grit waterstone, but can only get "hair shaving" with at least a 1K water stone and plenty of stropping.
That's really the only one I care to weigh in on though, since I haven't sharpened an edge that would whittle hair free-standing. I can widdle if I hold the hair taught, but what would one call that?
In any case, how "sharp" something is can be hard to define. Do you define it by how well it cuts something? If so, then a nice piece of dental floss is much "sharper" than any knife edge when it comes to cutting cheese. Is it a matter of scale, as in the edge needing to be a certain dimension? If so then couldn't it be easily defined by grit size?
Personally when I think about getting something as "sharp" as possible, I'm thinking in terms of scale, but this "scale" really only relates to the width of the very edge. What about how obtuse the angle the bevel forms is? It's only logical to consider that an edge ground at the same grit, which would be the same width at the edge, would vary in performance depending on how thick the bevels of that edge are.
In any case, at this point I'm mostly just pointing out what others already have said, but as far as I'm concerned hair shaving and "whittling" ( whether done free-standing or not ) is as sharp as I ever need anything to be. Of course, my ultimate goal would be an edge so sharp I could not even brush it without it cutting me, but so far I haven't seen anything like that, and even that would have the same amount of variables that cutting hair does. I mean, I can't cut my finger just by touching my edges because I have giant callouses from playing guitar; on the other hand my friend has done it twice.
At the end of the day though, I tend not to worry anymore about if I can push-cut phone book paper with every knife because I know that most of my actual practical purposes for using a knife won't surpass that level. On the other hand, some knives I keep very polished because I like to shave with them and these ones do need to be able to slice through phone book paper like it wasn't there; however, a lot of my "cardboard cutting" knives are left at a 220 grit finish that won't cut phone book paper, but slice through cardboard with much more convenience.
As far as finding a standardized material to test, there are lots of materials out there that are produced with very tight quality controls. You can order plastic stock that would be great for this kind of testing. On the other hand, there are more variables like that to consider. Temperature, relative humidity, the age of the material, how it's been stored, and then of course there's the variables with the test operator and the human error.
Somehow I feel like they should just come up with a commercial CARTA machine...
These are the instructions to the EdgeTester. I've also been using one for quite a while; it really saves on paper costs when it comes to sharpening knife for someone else, and you can find imperfections or deformations with the edge of it better than you can with a Bic pen--and yes I've tested.
The problem I have with the EdgeTester is two-fold. One is that, it's a very subjective tool. Then again most methods of doing this are, but on the one hand the instructions recommend using "a new razor blade" as a benchmark, and the user then has to feel or "bumps". Well, what if it's been a while since they tested on a new razor, or what if their own edges feel smoother than a new razor?
Instead of an Edge "Tester" I see it as an indicator since it's more useful for finding things that are wrong than gauging sharpness, because as far as the EdgeTester goes, blades that have gotten a full 100 point score won't shave or cut up phone book paper.
It's still a really useful tool to have for finding deformations and imperfections, and as far as "rating" edges go... If instead of a 45 degree angle, you hold the edge tester at a much more acute angle, you can sometimes get a good indication that one edge is much sharper than the other like this. So it's also pretty darn flexible.
Anyway, enough about that... I've been wrestling with this topic of discussion for a while.
"Hair popping" is one in particular I find interesting, because I don't see "hair popping" being the same as "hair shaving". As I've said before, if the hair "pops off" and has to land somewhere, then potential energy was put on it by the drag of the edge, and once it makes its way through the potential energy is released. On the other hand, hair shaving glides through the hair with no pull or friction, and leaves the hairs laying in a neat pile. I can get "hair popping" off of a 220 grit waterstone, but can only get "hair shaving" with at least a 1K water stone and plenty of stropping.
That's really the only one I care to weigh in on though, since I haven't sharpened an edge that would whittle hair free-standing. I can widdle if I hold the hair taught, but what would one call that?
In any case, how "sharp" something is can be hard to define. Do you define it by how well it cuts something? If so, then a nice piece of dental floss is much "sharper" than any knife edge when it comes to cutting cheese. Is it a matter of scale, as in the edge needing to be a certain dimension? If so then couldn't it be easily defined by grit size?
Personally when I think about getting something as "sharp" as possible, I'm thinking in terms of scale, but this "scale" really only relates to the width of the very edge. What about how obtuse the angle the bevel forms is? It's only logical to consider that an edge ground at the same grit, which would be the same width at the edge, would vary in performance depending on how thick the bevels of that edge are.
In any case, at this point I'm mostly just pointing out what others already have said, but as far as I'm concerned hair shaving and "whittling" ( whether done free-standing or not ) is as sharp as I ever need anything to be. Of course, my ultimate goal would be an edge so sharp I could not even brush it without it cutting me, but so far I haven't seen anything like that, and even that would have the same amount of variables that cutting hair does. I mean, I can't cut my finger just by touching my edges because I have giant callouses from playing guitar; on the other hand my friend has done it twice.
At the end of the day though, I tend not to worry anymore about if I can push-cut phone book paper with every knife because I know that most of my actual practical purposes for using a knife won't surpass that level. On the other hand, some knives I keep very polished because I like to shave with them and these ones do need to be able to slice through phone book paper like it wasn't there; however, a lot of my "cardboard cutting" knives are left at a 220 grit finish that won't cut phone book paper, but slice through cardboard with much more convenience.
As far as finding a standardized material to test, there are lots of materials out there that are produced with very tight quality controls. You can order plastic stock that would be great for this kind of testing. On the other hand, there are more variables like that to consider. Temperature, relative humidity, the age of the material, how it's been stored, and then of course there's the variables with the test operator and the human error.
Somehow I feel like they should just come up with a commercial CARTA machine...
zyhano
Gold Member
- Joined
- Dec 3, 2009
- Messages
- 1,593
Tnx kennyb, good answer.
So you'd define those in the order - going to sharper -
Hair popping
Shaving sharp
Hair whittlling sharp
i'll add those to the first post.
So far it seems push cutting sharp, taut hair whittling and facial hair shaving sharp are also eligeble for this list. Where would these fit?
So you'd define those in the order - going to sharper -
Hair popping
Shaving sharp
Hair whittlling sharp
i'll add those to the first post.
So far it seems push cutting sharp, taut hair whittling and facial hair shaving sharp are also eligeble for this list. Where would these fit?
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