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Lets hear some advice.
- Thread starter muni
- Start date
the tear drop shape is ok at the outset, but as it gets sharpened more and more, the edge of the knife gets thicker and thicker, and becomes a lesser and lesser effective cutting instrument...that is why i hollow grind my knives (most of them)....the thickness of the blade is about the same for the last half of the profile, and you can sharpen it forever (well not really) with no change in the edge thickness or performance. hope this helps.....flat ground blades have the same problem...i saw this early on, had many randalls come to my shop to be sharpened and they had already had the edges moved up almost 1/4" and were too thick to have an effective cutting edge any more.
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http://www.mayoknives.com
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http://www.mayoknives.com
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If we're talking about factory type blades, I think it's all a money/time issue. Flats and hollows are easy to achieve with automated machinery, while "teardrop" grinds require a fairly skilled hand, and the time to do it. I respect Tom for his hollow grind point of view, but do not share it. Unless a blade is a full hollow grind (such as a straight razor) the initial edge bevels are thick to the point of creating a wedge effect when cutting. This is the paradox of steel/grind/edge geometry. In order for the blade to resist chipping, when at a usable hardness level, the edge must be thickened to add support. While there are similar problems that could be encountered with the convex/flat grind, most of the problem can be resolved by finding a combination of hardness, and blade geometry that will allow the maker to grind the blade in such a way, that there are very small, or no edge bevels. Hey Tom....are you gona be at the Blade show? I'd be interested in talking some more on this subject. Take Care for now!
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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
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Ed Caffrey
"The Montana Bladesmith"
www.caffreyknives.com
- Joined
- Aug 1, 1999
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- 3,036
Ed, I don't think Tom will be there, but I will. Generally I agree with Tom and would like to chat about it some. Personally, I think there are merits to both flat and hollow grinds, depending on the application of course. But, if you draw a straight line from the spine to the edge on a hollow ground blade, the only thing that is different from the geometry of a flat ground blade is all the unneeded steel that's been removed. It's basically the same as an I-beam. IMHO
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Jerry Hossom
www.hossom.com
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Jerry Hossom
www.hossom.com
Cliff Stamp
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To clarify, when they sharpen the blades (Muni is a friend of mine) the motion is along the primary (and only) convex grind, thus the profile thins out, not thickens, with use and sharpening.
-Cliff
-Cliff
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I believe flat or convex grinds have to thicken as they are sharpened, since you are eroding the finer primary grind and actually creating a secondary grind with the new bevel as you sharpen.
In my experience with sharpening flat ground blades for customers, they actually tend to evolve into convex grinds as the blade wears and is repeatedly resharpened. I have had to do some slack belt grinding on some of them that were particularly worn just to get them to a point where a useful bevel could be applied. Obviously that experience is with factory knives which aren't generally as wear resistant as the better quality steels used in customs. I'm speaking of the Shrade, Buck, Gerber, etc. hunting knives when I say that. They are made to be easily sharpened and that usually means easier to dull as well. And while many of these are "hollow" ground they seem to be ground on very large wheels so the hollow is not very pronounced and their shape and wear geometry is more like flat ground blades than the deeper hollows on most customs.
As for the "tear drop" shape, less expensive blades are often ground that way, even on wheels. since it removes much of the need for precision grinding, ie. there is no real grind line. My guess is that most of these are stone-ground on very large wheels with the goal being to simply create a workable edge, while removing as little steel as possible. If you wanted to turn a tempered car spring into a knife blade without retempering, that is likely how you would do it.
My thoughts anyway.
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Jerry Hossom
www.hossom.com
In my experience with sharpening flat ground blades for customers, they actually tend to evolve into convex grinds as the blade wears and is repeatedly resharpened. I have had to do some slack belt grinding on some of them that were particularly worn just to get them to a point where a useful bevel could be applied. Obviously that experience is with factory knives which aren't generally as wear resistant as the better quality steels used in customs. I'm speaking of the Shrade, Buck, Gerber, etc. hunting knives when I say that. They are made to be easily sharpened and that usually means easier to dull as well. And while many of these are "hollow" ground they seem to be ground on very large wheels so the hollow is not very pronounced and their shape and wear geometry is more like flat ground blades than the deeper hollows on most customs.
As for the "tear drop" shape, less expensive blades are often ground that way, even on wheels. since it removes much of the need for precision grinding, ie. there is no real grind line. My guess is that most of these are stone-ground on very large wheels with the goal being to simply create a workable edge, while removing as little steel as possible. If you wanted to turn a tempered car spring into a knife blade without retempering, that is likely how you would do it.
My thoughts anyway.
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Jerry Hossom
www.hossom.com
with obvious differences here, i will throw my two cents in again...i have to agree with ed, that done properly and for the right task, the tear drop shape is great, but as mentioned above, the whole knife must be reground to keep the original shape, while a hollow ground knife can be resharpened again and again with the same angle, and yes, it is two flat surfaces, like ed says, but it works...i make all my machetes and camp knives with flat grinds that end up with some convex...but they are for slicing and strength, whereas most of the hollow ground blades are for cutting up game. In most of my combat type knives i use 1/4" steel, and dispite what some on this forum say, i very seriously doubt if you could even tweek one of these without some sort of aid....we all do what we think is best with the ideas we have....i totally agree with ed, but i dont make the same type of knives he does and have never forged anything in my life... like I always say...life is like the lady of justice, whatever you put on one side of the scale makes the other go up, and visa versa (fancy word for the other side is true for you people from the deep south!!)
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http://www.mayoknives.com
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http://www.mayoknives.com
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Ed, Tom doesn't really agree with you. It's just his roundabout way of disagreeing with me, beause my side of that scale is a little heavier than his...
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Jerry Hossom
www.hossom.com
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Jerry Hossom
www.hossom.com
Cliff Stamp
BANNED
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Jerry, in the blades Muni is discussing, the "tear drop" shape is not used to reduced initial grinding as the blades are all forged to shape.
-Cliff
-Cliff
Have you tried with both kind of sharpening before? And have you used it in actual working condition? And if you done so what is the outcome of this? In the forum no body have given me any what is the advantage of "V" shape or the "Tear Drop" shape grinding. What I am saying is that there must a purpose or good explaination for this.