Thin edge on HI?

Infi-del

Infi-del

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Apr 6, 2009
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Hey guys, Got an Annapurna last week and love it. I was grinding on it a little to try and get the edge a little more uniform. But I had a question. I'm a fan of thin convex edges and most of my blades have them. The Annapurna's edge is completely hardened per the folks at HI, so I was wondering if their steel can handle a thinned convex edge without chipping or denting. Never had much experience with their blades so I don't know if they're soft or extremely hard. Either would require a thicker edge geometery to keep from being damaged. Appreciate any info here.
 
You can go thin, but not too thin.

Since they heat treat by eyeball and a kettle of boiling water, each blade really is individual, and you have to learn what that particular blade will take.

All part of the HI experience.
 
Never had much experience with their blades so I don't know if they're soft or extremely hard. Either would require a thicker edge geometery to keep from being damaged. Appreciate any info here.
Click to expand...

Well, in my experience anyway, they're both. The edge tends to be extremely hard, around HRC 60-62, while the spine is about HRC 50, or even softer. In between, it's usually an exponential curve, very hard quickly going to very soft. It's often possible to acid etch a khukuri and see a definite transition between "hard" and "soft" steels, much like a clay-tempered katana.

Personally, I would leave well enough alone. If the khurkuri arrived with a thick edge, then it's intended to have a thick edge, for heavy duty chopping. I.e., if you buy a station wagon, it will always be a station wagon, even if you put a sports car engine in it! On the other hand, if you look at them in profile, HI blades tend to have scarily acute edges, sort of like a Finnish puuko. Here's a digitally enhanced photo of the edge angle on my Giant Chitlangi Bowie (24" long, 59 ounces!):

edge.jpg


If you want a khukuri with a thin edge, special-order one exactly how you want it. IMO, Sgt. Khadka and Bura would be the best ones to make such a blade. Sgt. Khadka especially is known for making fighting khukuris with wickedly thin edges. My chainpuri made by him is incredible, and has what I'd say is an absolutely perfect convex edge for a fighting blade. For a more "utilitarian" knife, I would ask Yangdu to have Bura make a Chitlangi with an especially thin edge. Vim would also be an excellent choice; he made the Giant Chitlangi above, and my regular Chitlangi made by him also has a very thin edge. My 15" Sher Sirupati actually has a slightly thicker edge than both the Giant Chitlangi Bowie and the 21" Regular Chitlangi.

Special orders cost a little bit more than a Deal of the Day, but they are definitely worth it!
 
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I would guess that blade came with a fairly thin edge but maybe not.
Probably best to thin it only a little before using it. Then see how it holds up.
 
Personally, I think you should sharpen it first. They don't always come all that sharp.

Ryan is right that the final angle is very acute. When I sharpened my 20" CAK, keeping the original angle, it will even slice thin grass with ease. Depends on what you want to do, really. Since yours is a knife, you can probably get it very thin if you aren't going to chop with it. Otherwise, try sharpening it, keeping the geometry it has now.
 
Great photo Ryan M, much appreciate seeing it and reading your comments. :thumbup:

Any photo's and info on your Sgt K Chainpuri (I assume it is one of the recent 18inch versions recently on the dotd?) would make informative reading!
 
Just have the short little review from a few days ago, so far, that I think you already read. For those that missed it: http://www.bladeforums.com/forums/showthread.php?t=709555

I haven't had the chance to really put the Chainpuri through its paces yet, just swinging it around, and some very light chopping on my trusty old 2x4 and some cardboard tubes. I really want to try cutting a 2 liter bottle, but it's freezing out and my neighbors would think I'm some kind of nut (well, I actually am some kind of nut, but I don't want them to know that!).

On cardboard tubes, though, it's without a doubt the best cutter I own. An entry level (Paul Chen) katana ties in terms of cutting ability, but is much slower, less maneuverable, much less forgiving of bad technique, and just less "effortless" of a cutter all around.
 
Generally speaking, as with pretty much all things, there is a trade off between a thick durable chopping edge and a high polished thin slicing edge. Obviously, the thinner you go the more likely a ding or roll or chip could happen.

That said, I have several HI khuks with a thin convex edge that have stood up to a LOT of abusive use with nothing more than sharpening required. Kumar used to make a fantastically thin edge:thumbup:

As others have said, try sharpening it first before going too thin. If you thin it out before you give it a good sharpening, you might find a layer of softer steel on the outside that would lead you to believing that that particular hardness is uniform throughout.

Sometimes during the hardening process the really hard steel settles beneath a good couple of layers of softer steel. This is where some of the mythic stories of khukuris actually becoming sharper as they are used comes from. That said, the harder the steel, the more likely it may be to chip if taken too thin.

The good news is that even if you take the edge down too thin and it chips a bit, it has PLENTY of hardened edge behind it to restore it to a fuller convex :)
 
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