Edge angle

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DocPat2511

Joined
Feb 15, 2001
Messages
340
Howdy folks.

I claimed the Kesar-made Chiruwa Sirupati Uncle Bill put up the other day; it came in today. STURDY beastie, and quick for its length and weight.

Its edge is hair-pulling sharp, and looks like it was just quickly buffed or fine-honed onto the primary bevel (at essentially no angle). I can either strop this down to something EVIL sharp or cut in my usual 30ish degree bevel and polish that up. I don't think if I just polished this edge it would stand up to much abuse. Also wonder if 30 is too steep for chopping chores.

Just wondering what edge angles the experts use?

[This message has been edited by DocPat2511 (edited 03-17-2001).]
 
I don't know khukuris, as many should have figured out by now, but 30 - 40 degrees is pretty much average for the circle of Euro-sword affecianados that I hang out with. Of course, the edge geometry, and intent of the blade is a good deal different between Euro double edged swords and khukuris.
Still, I would think that 30 degree bevel would be more than capable of hacking. I mean on most of the Euro reproductions they go through 1/4" plywood with no problem. They also can go through cardboard or paper, so it's still plenty sharp.

Time to digress
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BTW, I took my Malla out to prove her worth today. She conquered the trunks to several small trees that fell in our last major storm. One was about 2.5" to 3" in diameter. When I was done cleaning and running the chakma over the edge it seems that she took more hair than when I first recieved her! I didn't see any knicks in the blade, nor did it seem like she was dull, but I just love running that thing over the edge. I guess she just needed to get out and stretch her legs after being cramped up in that shipping box.
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I'm a wierd individual, I go for about a week or so trying to make sure that I keep the blade of a new purchase as pristene as possible, then I decide at some point that I need to find out what she can really do. When I'm done I'm always more proud of the little battle scars on the blade then I ever was of the unused blade.
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Oh, I got into my Malla because that thing had a rather thin edge on it, atleast given what percieved for a khukuri, and she held up better than I could imagine.

Bob
 
The convex edge looks like there is only a primary bevel at first glance. If you look carefully the primary bevel will have a curve to it (unless the Kami did this one differently). The convex edge gives better clearance for chopping. On all my khukuri's the original edge is great for chopping. They are usually a bit dull for efficient cutting.

I suppose you mean 30 degree per side (60 degree inclusive angle for both sides). A 30 degree bevel is recommended for heavy use and chopping according to the literature. If the angle is reduced cutting performance will improve but the edge will not be as tough. The edge will be more susceptible to rolling. I prefer 25-30 (closer to 25) degree on khukuri’s.

Will


[This message has been edited by Will Kwan (edited 03-18-2001).]
 
Thanks for the help, guys.

Will-I did mean 60 degree edge, I was talking about where to set my rods. That's the edge I usually put on tomahawks and "user" knives. I'll have to have another look at the edge to see if it is convex- never thought about it; I'm so used to production knives.

Bob-What sword do you practice? Where'd you learn? I'm interested because we're in the same neck of the woods and I may try to get some edged-weapon training in a few months.
 
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Doc I prefer to keep the edges of my khuk's pretty much the same convex radius they come with.
There's just something about having a very sharp And Strong edge with no angles or secondary radiuses.
It does take some practice to maintain the full convex edge and in my experience best done with the edge trailing on the sharpening stone.
And yet sometimes when I am tired I will lightly run the edge over a set of crock sticks set at a given angle a few times to bring the edge up.
But this is usualy so small that when I strop the edge with a tripoli charged strop it brings the radius right back to where it was.

And Uncle Bill sends me the dullest ones he has left over from sending Will's.
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>>>>---Yvsa-G@WebTV.net---->®

"VEGETARIAN".............
Indin word for lousy hunter.
 
Yvsa- Do the rolled edges (which is what I usually have called convex edges) stay sharp? I've never actually used one, but I understood they had a reputation for dulling easily (I'm completely ignorant on this one, so please feel free to correct me.) I imagine I could maintain it with a slack strop and steel.

Interesting how you mentioned putting a shallow edge on then stropping it round-that's pretty much what I'm doing to my 18" Sirupati. (When my strop paste gets here via OOPS; for most of my knives I just use bare leather to finish the edge after using the stone.) It was mostly out of laziness, though; just got tired of trying to cut an edge into that sweet spot and decided to see how it turned out after a few licks on the strop. Figured I could always take more off, but couldn't put it back on
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Doc the convex or rolled edge is the absolute strongest of all edges with more steel being retained above the cutting edge. And as always the quality of the steel and the hardness are what helps to determine edge life no matter the grind on the blade. And the convex edge is one of the best cutting edges as well since the blade follows the edge into the material being cut more
effectively.

On a hollow or concave grind the edge cuts nicely until the widest part of the blade is contacted and then the force to continue cutting becomes greater.
And on a flat ground blade the same is true except the edge grind stops at the spine of the blade and then more force is required to push the knife on through the cut.
A flat saber ground blade is even worse because the wide part of the blade is contacted much sooner and the edge grind is much steeper than
the true flat ground blade.

The khukuri has a convex edge but is not a true convex ground blade.
The true convex ground blade goes to the very edge on both sides of the blade and is wider somewhere toward the top and narrows again at the top of the spine.
(I wish I could say it better, but I hope that conveys the right idea.
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)
I can draw it better than I can say it and I may try that later in the day after the errands are done.

If you have a Marble's Woodcraft or Fieldcraft or have seen one and can recall the blade's shape from edge to spine then it all becomes clear as they are good examples of true convex ground knives.

Later.
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>>>>---Yvsa-G@WebTV.net---->®

"VEGETARIAN".............
Indin word for lousy hunter.
 
I think I got it. Like a lens in cross section, with one "point" flattened.

OK, ya talked me into it. I'm going to try cleaning up the convex edge. And if I blow it, it's your fault, Yvsa!
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But not now. Post-call and exhausted at the moment, and my major task will be to get home without wrapping myself around a tree.
 
For wood chopping, I believe most axes have a convex grind. I am not sure about this though.

Will
 
:
You've got it Doc.
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And you can always change the convex to a regular bevel grind if you don't like it, but I'm betting you will.
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And Will all the axes I have ever seen have had convex edges.
And hatchets as well....

Almost all the old timey tools and knives had the convex, clam shell or apple seed edge.
The old timers knew that this was the strongest edge possible and with a premuim on steel, even in this country, it wasn't wasted.
Many implements were made of iron with steel edges forge welded on.
They were hell bent for tough made that way.
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------------------

>>>>---Yvsa-G@WebTV.net---->®

"VEGETARIAN".............
Indin word for lousy hunter.
 
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