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Thread: Razor sharpness compared to other types of blades

  1. #21
    ace
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    Senior Member blabbermouth ace's Avatar
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    Before we drag this horse off to bury him/her, one question. Is there an additional component in sharpness is addition to the width of the edge and the smoothness of the sides of the bevel? Is that third component the angle at which the bevel sides extend away from the edge? It seems that the width of the very tip of the edge and the angle of the bevel sides might be necessarily connected, but I'm not sure that is the case. Wouldn't it be possible for the very tips of an acute angle and a slightly less acute angle to be equal and yet the angle formed by the bevel sides be different, thus affecting ultimate sharpness?

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    Senior Member Blackpool's Avatar
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    Right, I hope I am following this. On these last three responses, for which I am very grateful, would it be a fair assumption, borrowing your terminology, that the ultimate sharpness of the apex of the bevels is set at 4,000 whilst the bevel faces are further refined by subsequently higher grit stones, and furthermore goes some way to explaining why some people are greatly alarmed by the practice of taping because, I am guessing here, that would deepen the angle of the bevel and in doing so, make the bevel faces shallower?

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    aka Jeff Clark
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    I'm going to repeat part of what I posted earlier in this thread:
    "Shaving sharpness depends on the thickness of the apex of your edge (say .3 micron), the included angle of your edge bevel (say 10 degrees), and the rest of the bevel/blade geometry for a distance a bit wider than the thickness of your beard hair. Beyond these geometric characteristics a shave depends on the microstructure of the edge (call that localized roughness or granularity) this depends some on honing tools/techniques and some on blade alloy. A straight razor is not only honed at a low angle, the blade thickness behind that edge is almost straight (zero degree angle) behind the edge due to the hollow ground profile."
    Boy you know you are pompous when you start quoting yourself.
    Again you learn a lot from trying to cut off a stick with a Boy Scout knife. How you cut through a tough cylindrical material depends a lot on the thickness of your blade up to the point where you pass all the way through the material. If you have to cut at about a 45-degree angle to slice through your blade thickness at 1.4X the material diameter is significant. My old scout knife did the job better than my Buck folding hunter which was better than my old pick-lock switchblade.

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    Senior Member LoriB's Avatar
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    I know this probably a mistake to wade in here since you guys are getting techinical but here's my two cents from observation of people talking about swords. I do love katana, the traditional ones that take an army of people months to make not the ones that one guy hammers out in his back yard and sharpens up in a day. I've read books, watched documentaries and talked to people on the subject. As much as I love and respect them I have to point out one thing. A commonly used catch word for "sword" is "blade" as in when someone asks "What blade is that" they are really asking "What brand is your sword?" I've heard "blade" used interchangeably with "sword" in documentaries too saying things like "Katana are the sharpest blades ever made." (That point is also contested by European sword collectors btw.) The people watching the documentary then thinks "blade" means any sharp instrument and misinterprets. They then go around saying they have it on good authority that "Katana are the sharpest things ever made." See where I'm going with this? The blades aren't the problem. It's the choice of words.

    Lori
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    Senior Member blueprinciple's Avatar
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    Some years ago I was using a hanging strop and a 'noise off' startled me, making me forgot to flip the razor at the end of the stroke. It then on the next stroke simply carved its way straight through a 2.5" wide piece of cow leather over 1/8" thick, leaving me with two strops for the price of one! I mean, how sharp do you want these things to be? And as for katanas et al, I don't really suppose it matters to the less skillful combatant as he sadly contemplates his missing arm/leg/head that his sword was sharper than his adversaries'.
    BTW I saw a test recently tween European Broadsword and katana on cutting through straw ricks etc. Both had about the same cutting power. So I guess it depends who practiced most when it came to a scrap!

  7. #26
    Senior Member blabbermouth Kees's Avatar
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    May I recommend Experiments on Knife Sharpening - John Verhoeven ?

    John Verhoeven is an authority on sharpening issues who did a lot of scientific experiments.
    Plus ça change, plus c'est la même chose. Jean-Baptiste Alphonse Karr.

  8. #27
    Senior Member Caledonian's Avatar
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    The katana actually has a rather obtuse cutting angle, even as swords go. It also has something that most European makers, including myself when I dabbled many years ago, consider anathema, the blade near the edge is actually convex, so that there is no line where the edge bevel joins the rest of the blade. This convexity of the blade is called "meat" in Japanese, and is considered crucial to catching the right balance between cutting ability and durability of the edge.
    In fact there is quite some controversy among collectors and the swordsmiths who still make them. There is a tendency for enthusiasts in the sport of cutting straw-mat bundles to want swords with so little "meat" that they would be damaged by other use, and purists think this degrades the art of the Japanese sword.
    There is, however, a variable with any curved sword which barely exists with the razor. The katana is curved, and inclines backwards from the handle. This results in the blade meeting its target at an oblique angle. The true cutting angle is the one at which blade to targe movement takes place, and is thus more acute than it seems.
    I have a couple of books with interesting insight from India. The less surprising of the two is "Cavalry: Its History & Tactics" by Captain Louis Nolan, who played an uncertain role in sending the Light Brigade down the wrong valley, and was the first man to die in the Charge. He describes seeing fearful wounds inflicted by swords carried by Indian irregulars, but on examining them, found that they were surplus British army blades, rehilted, kept in a wooden scabbard instead of a steel one, but most importantly of all, made far sharper than they used to be in the British service.
    The other is "Reminiscences of the Great Mutiny", by the former Sergeant William Forbes-Mitchell of the 93rd Highlanders, who unfortunately has left no record of standing in the Thin Red Line at Balaclava, but writes of the Indian Mutiny, in which the regiment stormed the Sikander Bagh to relieve the siege of Lucknow. His service did not require a sword, but he saw a great deal of death and wounds inflicted by them.
    His conclusion was that western swords, made of something very much like spring steel and tempered to withstand the rather pointless of test of being bent into strong sideways curvature, had far less wounding power than those of Damascus steel, by which he presumably meant the Indian wootz steel which used to reach the west through Damascus. He held that being more rigid and deader in the hand, they wasted less of the impelling force by bouncing and vibrating.
    I know some scalpels (I use the term with non-medical vagueness) can be as shallow-angled as razors. Supporting evidence for this is that obsidian flakes are used for certain types of surgery, even nowadays, and why would they do that, if they had never needed to extract the maximum possible sharpness from steel? Others, intended to contract bones, cartilege, tendons etc., were probably less sharp. The validity of cadaver tests in forensic ballistics, or evaluating weapons, is often held to be compromised by the fact that medical cadavers, being in short supply, are refrigerated and treated with preservatives, both of which toughen the tissues.

  9. #28
    Senior Member adbuett's Avatar
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    Clinicon Diamond Scalpel

    Very impressive.

  10. #29
    Senior Member blabbermouth Kees's Avatar
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    Ever shaved with one?
    Plus ça change, plus c'est la même chose. Jean-Baptiste Alphonse Karr.

  11. #30
    Geriatric Gamer/Surf Fisher tonycraigo's Avatar
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    Quote Originally Posted by adbuett View Post
    Clinicon Diamond Scalpel

    Very impressive.
    "Now, Mr. Smith, we'll just lance that boil with this diamond scalpel... there we go... feel better? Keep that hole filled up with neosporin. Just see Ms. Jaberwathy on your way out..."

    "Hello Mr. Smith, unfortunately your insurance only covers boil lancing with a straight razor... That'll be $500,000.00 and We accept Visa, Amex and cash. How do you want to pay for that?"
    Last edited by tonycraigo; 05-12-2011 at 11:43 AM.

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