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Post by wolf_shade on Mar 21, 2012 14:19:54 GMT
So, I did a search on sharpness and saw a lot about it being a good indicator for sword quality, important piece of cutting success, factor in the danger in careless handling etc. etc. However, I didn't see anything to determine how sharp your sword is (even to the extent of "sharp enough vs needs a touch up"). I know that "shaving sharp" and "paper cutting sharp" are terms often used both in this forum and in sales pitches. But are these good tests to determine the sharpness of the blade (I'm assuming shaving sharp is not)? Is there a level of ease with which a sword should cut paper, an amount of fraying that occurs on the paper with the cut, etc. that can be an indicator of more or less sharp?
I say all this because I've just received my first real, viable, non-wall hanging, designed for use, katana (Ronin Dojo Pro via S&D sale). I'm interested in doing some cutting as just a back yard hobby/time waster. (Frankly it's all your, the SBG forum at large, fault. If I hadn't seen cutting videos...) So I want to know how to tell 1) My sword is as sharp as it needs to be cut. 2) My sword has begun to dull but is still usable to cut. 3) My sword has dulled to the point that it should be sharpened before continuing to cut with it. I'd prefer some objective method because "when you start batting bottles around" seems too dependant on other factors to be reliable. "You notice an increase in resistance" might not be usable overall either. Historically I've had a habit of not noticing changes other people think I ought to be aware of, so I'm not sure I'll notice the difference in resistance, especially if it is a gradual decrease (sort of like a frog in a pan on the stove).
My targets are going to be bottles of varrying thicknesses. I doubt I'll ever attempt tatami as it's too expensive to purchase just for the sake of destroying it. Same with pool noodles. I might try the rolled newspaper thing if I can find a cheap (read free) source. Although if newspaper would be rejected for recycling after being soaked I'll just stick with bottles since the post-cutting plastic will find its way into the recycling bin.
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Post by Lonely Wolf Forge on Mar 21, 2012 14:31:13 GMT
i dont know about everyone else, but if it wont cut paper IMHO its dull as F**K and totally worthless until resharpened. that being said, it doesnt have to be that sharp to cut paper..
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Post by ineffableone on Mar 21, 2012 14:47:06 GMT
Shaving sharp swordShavingWithSwordOf course this guy has shaved with all sorts of blades, as he mentions in the video. But it is showing a sword literally shaving sharp
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Post by ineffableone on Mar 21, 2012 14:58:31 GMT
OK a more serious answer, since this is a good question and deserves some seriousness. Honestly I think paper cutting sharp is about where you know you need to resharpen your blade. Also testing your blade the length you will find different areas will dull sooner than others, for the obvious reason this is where you cut most. There are varying degrees of being able to cut paper also listed in order of dullest to sharpest. Rough tear, straight fine cut, and able to cut curving cuts. You want to at least be able to get a rough cut in paper for your sword edge, hopefully a straight fine clean edge cut in paper as it is a keener edge. The ability to cut waving curving cuts in paper is indicative of the sharpest razor sharp edges. Remember however, sharp edges mean more likely to be damaged. I suggest making sure you have a good convex edge since your doing bottle cutting as convex edges are stronger, and you don't need more than a fine straight paper cut, and can still cut bottles with a rough paper cut. Hope that helps
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SeanF
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Post by SeanF on Mar 21, 2012 15:12:44 GMT
I have cut quite well with many blades that are not paper cutting sharp.
The basic test I usually use is to see if you can have the sword bit into your finger nail. If you can apply presure and it starts to bit then it is probably good, if it just slides off it needs to be sharpened.
That said there are several levels of usable sharpness. I usually use in order of increasing sharpness: Unusable->Fingernail->Paper Cutting->Shaving
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Post by ShooterMike on Mar 21, 2012 15:26:29 GMT
I think you guys are thinking only in terms of Japanese swords, intended specifically for "demonstration cutting." If that's all you're interested in, you have a good answer.
However, if you are referring more broadly to all swords in general, then the answer is most certainly incomplete. There are many different types of swords, intended for varied fighting styles and periods in history. To say these all need to be sharper than paper-cutting sharp is completely in error. Many historical sword types were not nearly that sharp, nor were they intended to be. They won't even perform their intended function with an edge that keen, and thus that fragile.
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Post by ineffableone on Mar 21, 2012 16:12:55 GMT
I was answering the OP, as he said he had a katana. Though I did mention how sharp means more likely to damage.
Though I do think it would be cool to get some other blade style reference in here too. I think this is a good subject as many people think they need a razor edge, which is not really true.
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Post by ShooterMike on Mar 21, 2012 16:50:54 GMT
That's exactly what I was thinking. I thought I had read through all the posts, but missed much of your info.
This is a subject I wrestle with on an on-going basis with cut-oriented and cut&thrust swords. The sharper my swords are, the better I cut with them. But is that really what I want? No, not really. I want to learn how to use the weapon in hand, with a high degree of skill. How it cuts is a part of that. But not necessarily the important part. The important part to me is, how well I can cut with a particular cut-oriented or cut&thrust sword, when that sword is of a sharpness and edge design that is "historically approprate" and all that jazz.
Really, anyone with a very slight degree of skill can cut well with a sword of extreme sharpness (good paper-cutting sharp and will take off some hair). Someone with well-developed skill can make the same or similar cuts with a sword which has more of a degree of sharpness appropriate for the battlefield or extended use in a civilian context. For instance, a single-hand arming sword appropriate for a European knight or man-at-arms in the first 3 crusades would not be sharp enough to shave hair, and likely not sharp enough to slice paper very well. It might slice paper a bit, but its edge would have enough robustness to survive high-speed impacts on wood and iron shields, maille, and iron or steel helms. That usually would preclude ultra-performance on tatami and especially on extremely light targets like plastic water bottles. It would cut through non-leather clothed flesh like the proverbial "hot knife through butter" if the user has a good degree of skill. But lacking that skill, it wouldn't cut flesh nearly so well and wouldn't do well on plastic water-filled bottles....
...And that's where my argument starts. Anyone, regardless of skill, can cut light targets with an extremely sharp sword. So who cares? They aren't really developing any considerable level of skill with the sword. Just learning to slice bottles with a long razor. But if you work to develop the skill to make those same beautiful cuts with a sword of appropriate battlefield sharpness and edge robustness, your skill increases by a huge degree. Same with cutting tatami.
Maybe I'm just a sword fanatic, but every time I see someone doing beautiful silent cuts and such I wonder, "Are they that good? Really? Or is an overly ultra-sharp sword doing most of the work, compensating for not so great cutting skills?" So, what do you want? Sword handling cutting skills? Stunts that look good, but don't really require a lot of skill? Only you can answer this question for yourself.
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ghost
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Post by ghost on Mar 21, 2012 18:10:19 GMT
There are objective sharpness tests out there: An example: C.A.T.R.A. Test One of a handful of machines like it in the world, the CATRA tester uses controlled pressure, stroke length, number of cycles and a certified sand-impregnated paper to determine the sharpness and edge-holding capabilities of a blade.
* CATRA stands for Cutlery and Allied Trades Research Association.
Of course factors that will influence the reading -that I can think of: 1. HRC (including type of steel, DH or TH) 2. geometry of the cutting edge (razor thin or thick?)
Paper cutting is a pretty decent "specification" so I know that it is not DULL and can be cut with.
The phrasing of your question of "how well does a sword cut because of sharpness?" is not 100% there:
There are too many factors (especially your cutting ability) to get a definitive answer. If you have seen the "Weapons that Made Britain" , there is a cool "test" in there that measures force and thrust strikes (notwithstanding human error). I think that test would better answer "how well does a sword cut or stab."
Sharpness is a small measure; If you have good technique (form, stance, and edge alignment) you have the ability to cut well. Whether your tool is up to par doesn't have anything to do with your abilities. Like Mike said, if you can cut with a not so sharp sword - you have the slightest hint you are doing things right.
I don't cut with swords, merely collect them. But of you ever have handed a knife to someone who isn't familiar with them - you will cringe at the things he or she does wrong. There is nothing wrong with the knife - just the skills of the user.
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Post by wolf_shade on Mar 21, 2012 18:36:05 GMT
Ah, a fellow literalist. Which is pretty much what I was interested in knowing. So by this test I know that the Ronin came sharp enough to cut with out of the box (which is what I was expecting but it's good to have a means of verifying), and later if my form improves but the cuts start having issues anyway I have a separate means to test the swords sharpness to determine if the failure is my own or an indication that the sword needs sharpened. True. However, somewhere between my Starfire blunts that have a 1/16" wide edge and the scene from The Bodyguard where a piece of silk falling cuts itself on a stationary blade edge is the ideal sharpness for light target cutting with sufficient blade reinforcement to avoid damage in a bad cut.
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Post by wolf_shade on Mar 21, 2012 18:47:35 GMT
Surface level these two statements seem contardictory, so I will state what I think you mean and you can tell me if I've got it right or misunderstood. If all you achieve cutting paper is a rough tear, the sword is at minimal sharpness and needs sharpened. If you can get a straight cut that is a cut and not just a straighter tear, the sword is sharp enough for light targets. If the sword can do wavy patterns in the paper it might be too sharp.
To illustrate: I have a Masahiro Cherry Blossom that when I tried to cut a piece of paper held by one hand the paper just bent and there was no cut. I tried to do the same thing with a stainless steel wall hanger that I'm learning to sharpen on (TomK's guide and a few other people suggested practicing on other blades so I've been trying to). All I've done to it so far is remove the secondary bevel with a mill file. It made downward progress through the paper that was mostly straight but left ragged edges. I tried to cut with the new Ronin and it cut cleanly and curved slightly as it finished.
So the Cherry Blossom is in dire need of sharpening, the wall hanger is in need of finishing, and the Ronin is either sharp enough or borderline too sharp.
I believe it does, yes. Thank you.
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Post by wolf_shade on Mar 21, 2012 19:03:33 GMT
I guess this is what I was asking, but did not provide enough information to accomplish. I do not have any interest in performance geometry blades like the Cheness SGC, or ultra-sharp blades. I want to have a means to determine when my sword has become duller than it should be given it's geometry and type. For now that means katana. Hopefully it will eventually include some european origin blades as well.
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Post by Lukas MG (chenessfan) on Mar 21, 2012 21:28:40 GMT
For me, a blade's too dull when it doesn't perform the way it's supposed to, i.e. batting bottles when it cut them just fine half a year ago.
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Post by ShooterMike on Mar 21, 2012 21:41:03 GMT
I hold a piece of printer paper (or equivalent) in my left hand and the sword in my right. I use the sword the same way I would use a carving knife if the paper was a turkey. One continuous slice with light pressure on the paper should slice off a piece of the paper, using about 5-8 inches of the blade's edge. Repeat at different areas of the edge.
If it slices quickly and cleanly, I consider the sword "very sharp". If is tears a little, but still cuts the paper, I consider it sharp enough. If the blade bounces on top of the paper, barely grabbing it a little, it's starting to get sharp (or dull) but really isn't. If it causes the paper to simply fold out of the way of the blade and doesn't even tear, it's dull.
That test only applies to swords that are designed to cut as a primary part of their offensive function. But I fugured everyone on this thread is really only talking about cutting swords, as opposed to those primarily or mainly intended for thrusting attacks.
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Post by Deleted on Mar 21, 2012 22:00:38 GMT
Us old knife and woodworking tool sharpeners have a technique which tells you when a blade is sharp on a practical level and when it needs resharpening, and is the only real test you need for swords. Put the edge against the back of your thumbnail at an angle with the blade edge facing the tip of your thumb, and move the blade gently (or your thumb) so the blade moves towards the tip of your thumbnail. If the blades catches and digs in to the back of your thumbnail, it's plenty sharp, and if it glides off without catching, it needs resharpening. Test along the length of the blade and touch up any blunt spots with a diamond hone until they 'catch' and work your way along the length of the blade.
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Post by ineffableone on Mar 21, 2012 22:16:49 GMT
Pretty much you got the basic understanding, however one addition, a rough tear cut is a better edge for hard targets. As it will have more strength. And yes your examples of different swords and their ability to cut is perfect illustration. For water bottle cutting, a keen edge like the one on your Ronin is sharper than needed, but will dull in time as you cut. When you do need to sharpen it, test with paper, and only try to get it to a smooth straight cut instead of the keen curving cut paper. As has been mentioned, technique is a major player too. With a rough tearing cut in paper edge you can still get smooth clean cuts in bottles, but you need to have better technique and edge alignment. Glad my explanation made sense to you and you had the real world examples to visualise it.
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Post by f.m. on Mar 22, 2012 15:43:50 GMT
I'd say there's another set of factors at work: overall blade geometry. A sword with a nice acute angle of entry overall i.e. a "skinny" u or v shape with not much meat above the edge but it tapers down to an edge that won't cut paper will still get silent cuts on bottles and breeze through tatami. (see greg's atrim XIIa.1 warsword video on youtube for this)
however, a blade with a thick edge with lots of meat won't cut as well, especially given the same "grit" it was honed too. honing the edge to a fine polish helps with that initial "bite" into soft targets, but in my experience, my thinnest angle of entry swords always cut the best if you remove all other factors, including honing. good ol surface area and friction physics i suppose.
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