Edge hardness

gurkha berserka

gurkha berserka

Joined
Aug 16, 2014
Messages
1,602
Quick question, probably been asked a thousand times. What is the Rockwell hardness of HI differently tempered swords? How hard is the spine?

Any information would be much appreciated.
 
The spine is left unhardened and is usually around 50-53 Rockwell. The edge is 56-58 Rockwell.
They are made pretty much the same as the khukuri.
 
My favorite CAK has a spine soft as lead. I know, because I used it as a hammer and it gets dimples like an Orange. CAK attack!
 
Rockwell 50-54 is the edge hardness -- after heat treatment -- of the premium axes made by Council Tool from 5160 steel, so it does seem high for an unhardened spine.
 
Moonw said:
My file says the same.
Click to expand...

Steve Tall said:
Rockwell 50-54 is the edge hardness -- after heat treatment -- of the premium axes made by Council Tool from 5160 steel, so it does seem high for an unhardened spine.
Click to expand...

yup and 54 is being optimistic. I think the hardness varies depending on what part of the edge. The closer you get to the tip the softer it gets while the sweet spot on a khuk is the hardest but even then it is not as hard as claims I have seen. I hardness tested some of my old khukuris many years ago and my hardest one was 56 at the edge. The one at 56 was one that someone had checked with a file and claimed it to be 60, lol. Most where closer to 54. And none where at or above 50 at the spine. All where much softer than that. Having said that, when you think about the amount of force you can create with a heavy khukuri or sword when you hit something, a slightly softer blade will survive heavy impacts.

People have done checks on hardness and I have yet to see one person come back with even 55

fullplate said:
Hi Guys
Checked my BAS at bolster end of blade on Rockwell tester, started at 29RC at back edge and rose to 40RC at start of blade bevel.Need to make a fixture to hold blade level to do the rest. By comparison my Cold Steel folder was 60RC all over.(its my EDC)
Regards
Phil
Click to expand...

slash-5 said:
Little bit about myself, I have made around 20 hand forged knives in my time, but am certainly not an expert.

I have a couple of questions:

I just got a 15" Ang Khola from HI. After cold bluing it (I hate shiny work knives), I decided to sharpen it. I started with a new, small sharp file and noticed that it "cut" into the steel a lot more than I was used to with large knives. (I have great working machetes from Costa Rica that it won't "bite" into). Anyway, I then tried a dull file and it cut pretty easily too. I would guess that the RC hardness is somewhere int he high 40's, but I have no way of verifying this.

It seems that the Khukri is softer than it should be. Now, I understand that larger blades should be softer than smaller knives because they need this to absorb the shock from heavy work, but this blade does not seem to be much harder than unhardened steel (34 RC?).

What do you guys think?
Click to expand...
 
I guess I should have clarified a bit more....but didn't have time.

The spine is left unhardened. It is whatever the spring steel is at after annealing and forging, usually somewhere between 40-50rc. The transition zone between the spine and edge is usually somewhere around 50-53 rc, progressing toward the harder edge at 56-58rc. As usual, these figures are a bit subjective and averages....and will vary a bit from kami to kami.
The important part, the "setting of the pine" is always the goal at 56-58rc.

Most of the swords are made the same way as the khukuri are, with the exception of the Everest Katana and possibly the wajaski (wakizashi) sword, which have a quench to give them the distinctive curve and causes a few more steps in the process. Master Kami Bura did a concerned study on Japanese swordsmithing and modified its parameters slightly to fit the environment and practices of the Bishwakharma.
 
Last edited:
Karda said:
I guess I should have clarified a bit more....but didn't have time.

The spine is left unhardened. It is whatever the spring steel is at after annealing and forging, usually somewhere between 40-50rc. The transition zone between the spine and edge is usually somewhere around 50-53 rc, progressing toward the harder edge at 56-58rc. As usual, these figures are a bit subjective and averages....and will vary a bit from kami to kami.
The important part, the "setting of the pine" is always the goal at 56-58rc.

Most of the swords are made the same way as the khukuri are, with the exception of the Everest Katana and possibly the wajaski (wakizashi) sword, which have a quench to give them the distinctive curve and causes a few more steps in the process. Master Kami Bura did a concerned study on Japanese swordsmithing and modified its parameters slightly to fit the environment and practices of the Bishwakharma.
Click to expand...

So the curve on my Everest and possibly the wajasaki are created through the hardening process much like the Japanese katana? I am very glad to hear that. I thought they were shaped that way. It's nice to know the blade forms naturally that way through the quenching process.
 
Last edited:
Well now, I guess that moves the Everest Katana from my "want really badly" list to my "buy without forethought" list... That's always been my favorite part about katanas, and one that has interested me since I was a kid
 
Cobalt said:
yup and 54 is being optimistic. I think the hardness varies depending on what part of the edge. The closer you get to the tip the softer it gets while the sweet spot on a khuk is the hardest but even then it is not as hard as claims I have seen. I hardness tested some of my old khukuris many years ago and my hardest one was 56 at the edge. The one at 56 was one that someone had checked with a file and claimed it to be 60, lol. Most where closer to 54. And none where at or above 50 at the spine. All where much softer than that. Having said that, when you think about the amount of force you can create with a heavy khukuri or sword when you hit something, a slightly softer blade will survive heavy impacts.

People have done checks on hardness and I have yet to see one person come back with even 55
Click to expand...

TBH, this is quite disappointing. I don't see how such low values on the hardness scale would be able to hold an acceptable edge on a knife. 57 is the minimum I consider acceptable for hardwoods in a knife (axes etc. may go lower) because of geometry.

Otoh, I remember Uncle Bill going to Nepal to sort things out as he said the Foxy Follies at 55 hrc were much too soft?
 
Last edited:
I mean it is disappointing if we are talking the sweet spot, where I would expect around 60. Poor edge retention -> frequent sharpening of an edge that anyway has a small depth of fully hardened metal. If you add that carbon may be lost during forging at the very edge or because of the polishing you end up with a knife with a very short lifespan.

This, along with other recent experiences, made me somewhat skeptical that the traditionally-made kukri is indeed a tool for hard use. I still wait to be wowed by any kukri, HI or otherwise.

I also don't see how such a knife would pass Uncle Bill's original test. I guess, on the average, the old kukris might have still been made with more care.

I am even considering a KLO just to make sure I get the expected quality that was claimed for the traditionally-made kukri to posess.
 
Last edited:
Plain and simple, HI's blade are effective in what they are meant to do, last several lifetimes, and backed by the best guarantee and customer service in the business, my question then becomes, does it really matter what the RC is?
 
cul4u01 said:
Plain and simple, HI's blade are effective in what they are meant to do, last several lifetimes, and backed by the best guarantee and customer service in the business, my question then becomes, does it really matter what the RC is?
Click to expand...

Of course it does, it does a lot. It is an intrinsic quality of the knife. Kamis 150 years ago were able to harden an edge not only on the sweet spot, but on the whole length without warping a blade, so now that we have metal of known origin and quality one would expect a few centimeters which is how long the sweet spot is, to be properly hardened.

A softer blade made to cut "zombies" is just fine; not so, with one made to cut wood.

Again, soft metal means more sharpening of a little portion of hardened edge (depth-wise). If you have 20 kukris that you cut every now and then some green pine, I guess it doesn't matter, but that is not how these knives are marketed as. So I am not sure about a few lifetimes of service out of any kukri? I've never seen a justification for this often made claim.

Add to this the fact that as far as I understand knives are not tested for hardness (or at least not all) and there is quite a risk in acquiring a traditionally-made knife, performance-wise. Somene that knows how to "read" a file mark or with a piece of hard wood I bet would make a difference.
 
Last edited:
Moonw said:
Of course it does, it does a lot. It is an intrinsic quality of the knife. Kamis 150 years ago were able to harden an edge not only on the sweet spot, but on the whole length without warping a blade, so now that we have metal of known origin and quality one would expect a few centimeters which is how long the sweet spot is, to be properly hardened.

A softer blade made to cut "zombies" is just fine; not so, with one made to cut wood.

Again, soft metal means more sharpening of a little portion of hardened edge (depth-wise). If you have 20 kukris that you cut every now and then some green pine, I guess it doesn't matter, but that is not how these knives are marketed as. So I am not sure about a few lifetimes of service out of any kukri? I've never seen a justification for this often made claim.

Add to this the fact that as far as I understand knives are not tested for hardness (or at least not all) and there is quite a risk in acquiring a traditionally-made knife, performance-wise. Somene that knows how to "read" a file mark or with a piece of hard wood I bet would make a difference.
Click to expand...

What I'm saying is that Bura explained it before, by watching the color changes during the heating process, he knows exactly where he wants the blade to be in hardness for it to be the most effective. In HI's case, they may not exactly what the RC is, but I bet they know exactly what part of each blade can and cannot do, and why.

I use my blades hard a lot during the year, never had a problem, they all seem to be hardened in the same area, at the same hardness, Most well made knives, if taken care of, will last a long time, several lifetimes for that matter. I have a village made machete from China, and it was handed down from my Great Grandfather, to grandpa, to my father,and then to me, and it was well used even before my great grandfather, only GOD knows how old it is, but it can still chop with the best of them, and hold it's edge. We've changed the handle a few times, but the blade is as good as it's ever been.
 
Last edited:
Of course that one would harden metal by observing the colors and quenchig at the proper time. This is what all kamis do. I remember the context, it is from. The HI website.

Was the machette used on hard woods as a kukri is expected to? How deep was the hardened section, initially? Even with steeling, stropping in-between etc. I don't see how, when sharpening, thus taking away metal, a knife that has a small portion depth-wise of hardened metal and one used hard would last long. As Uncle Bill said, kukris passed from generation to generation were Budhumes before becoming Sirupatis and made a few visits for renardening to the village kami ;).

A machete could very well be fully-hardened 1055 or similar at 52-55 HRC.
 
Last edited:
The sweet spot in Rc for 5160 is 56-58. When you go over 58 things go bad quickly. Differential HT does help things a lot, though. All steels have a range of Rc that they prefer and fall off quickly when you go over it. CPM3V does as well. So this is nothing unusual. When you are swinging a 3lb piece of steel you want toughness not high hardness. The Kami's have been making these blades for eons, I think they know what they are doing. I would not worry about it.
 
You must log in or register to reply here.
Back
Top