Fugglesby at KHHI: Hardening and smashing

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Fugglesby at KHHI: Hardening and smashing

Post by Fugglesby » Sun Jul 13, 2014 5:58 am

Hey guys!
My trip to Nepal is going amazingly. It's such an amazing country and has such beautiful people that it melts your heart. But you're here for knives! Specifically big ones. So far the majority of my time has been spent sorting out a proper heat treat for the 2 steels they have here to ensure that they can get the most out of the steel they're using., as you can see in the videos below.
Also you have YOUR FIRST GLIMPSE OF WHAT I ACTUALLY LOOK LIKE. Am I older? Younger? More australian?
Watch and find out.





So far the results have been pretty great! The 52100 was a pain in the arse, but eventually the durability was reached to an acceptable level. Did pretty well for a razor blade steel I'd say.
A big thanks goes out to Stormcrow, whose information on backyard heat treating 5160 served as a great starting point :)
And for those who are interested in what comes next, a clue!
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Re: Fugglesby at KHHI: Hardening and smashing

Post by Kutter_0311 » Sun Jul 13, 2014 7:52 am

5160 is the only steel commonly available? Or the only steel with any hope of making a useful knife?

I'm sure you could find 1018, but what's the point.
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Re: Fugglesby at KHHI: Hardening and smashing

Post by Storm Crow » Sun Jul 13, 2014 7:53 pm

I watched all the videos. Interesting stuff. Cool to see you over there. :)

Questions:

1. How does the performance of the new heat treatment compare versus the old way? The tea-pot method is understandable, but so backwards to how I work that I don't have a good gauge on what the performance was like.
2. Was the normalizing step completely new to the kamis?
3. Where was the steel sourced?
4. What were Saroj's thoughts on the new vs. the old?
5. Has Saroj considered adding a heat treatment furnace for hardening? While mine is a bit slower than using the propane forge, it is a lot more controllable and even in the heat (It's even an Evenheat brand!) and I am nailing the point of decalescence for normalizing and hardening with it. Liking it very much.

Looks like y'all have a winner with the 5160, and something workable especially for more slicey and less choppy blades with the 52100.

When doing the quench in the future, make sure the quenchant is closer to the fire so you aren't losing heat walking from the forge to the quench. 5160 is more forgiving than some steels, but you still will get better results if you pull out of the fire and quench with one smooth motion rather than travelling any kind of distance.

Also, if you can get your hands on canola over there, go with it. Different kinds of plant oils (and oils in general) will quench at different rates, and I've learned more about the complexities of quenchants in the last few months. Not that I know a whole lot more except to know it's more complicated than one would suppose. But canola is supposed to be just about ideal for a lot of simple blade steels.

And here's a good resource for heat treating blade steels in general: http://www.cashenblades.com/heattreatment.html

Glad I could help with pointing you in the general direction on the heat treatment. :D
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Re: Fugglesby at KHHI: Hardening and smashing

Post by Fugglesby » Mon Jul 14, 2014 12:47 am

Kutter and stormcrow, in answer to your questions, 5160 is the only viable forging steel which can be found in nepal and is also the traditional and time tested material. It's sourced from one of the multitudes of scrap steel merchants around kathmandu in the form of truck leaf springs. The other steel used is 52100 which is sourced from india as the CNC operations require both a highly annealed and flat steel in order to work. I've been told multitudes of times that it's the only steel available in india but I always thought this was fishy as hell what with all the car and tool production over there. SO I did a bit of research and found a source for some 1080 in reasonable sizes and quantities from New delhi, from one of the larger manufacturers which should be worth a try.

Onto the other questions:
1: The new heat treat is so much better that a comparison would be unfair, with the 52100 benefitting the most.
5160: THe old method is passable with the 5160. Due to being a very hardenable steel and deep hardening at that, the water actually does a decent job of hardening into the steel and not just the surface. THe issue though is that the manner in which it is applied to get the differential tempering is very imprecise and results in a very hard belly but an overly soft point and waist. While this potentially has benefits for durability and ease of sharpening, the kamis have all told me that it's unintentional and unavoidable, while I've also seen that the reduced hardness leads to the edge rolling far too easily and without enough edge stability. Once again, the temper being applied in the old method is terrible and hugely insufficient in my books. The edges exhibit sub standard toughness (though still good compared to non 5160 steel ) with small chipping at the edge when struck into steel or riverstone. In my opinion the knives are scraping by through sheer stoutness of edge geometry alone. It should be mentioned though that this is the method which has been used for over 200 years and serving ghurkas nor current customers have any complaints.
As for the new method, there are great improvements in every area. The entire edge is brought to sufficient hardness to skip a file, though with the tip softer than the rest of the blade. THe spine is more even with less hard spots from the teapot water splashing up and hitting it. This was all tested with rockwell files, no probes etc. The high temper brings the hardness down to a great mix of hardness and sharpenability, though the greatest improvement is definitely that of edge stability, where the improved temper has led to a higher retained hardness with a massive increase in toughness. THe final 5160 khukuri tested could be brought to shaving sharp with a file in the traditional way, then go through wood, horn and brick while still retaining sharpness. In the upper ends of the tests with the steel, concrete and riverstone, the sharpness was gone from the edges but we could induce ZERO actual edge damage (chipping or rolling) from chopping, batonning or prying while embedded in the material until I chopped directly into one of the pedestal grinder stands so the edge met the corner of the stand bang on. THe result was a slight amount of deformation, perhaps 1.5-2mm but no chipping or irreparable damage. Very happy with the 5160.

As for the 52100, it was in a much worse shape from the traditional heat treat. The water was simply not drawing enough heat from the blades at all, resulting in hardness which barely penetrated the steel at all, an issue after repeated sharpenings. These blades also suffered from a low overall hardness due to the lack of thermal mass, with the point and waist in my opinion being barely hardened at all. I ran the edge of a small oil quenched blade against the waist at one point and the edge wobbled out of shape with ease until it looked like a crinkle cut ship after a few passes. With that said though, the belly was very serviceable. I think it's lucky that they couldn't achieve higher hardnesses with this steel as the poor temper would've rendered them incredibly fragile and useless. That was the worst example I had encountered, but some of the 52100 knives had came out comparable to the traditional heat treat 5160. This lack of repeatability was an issue in itself.

After getting the modern heat treat right the results were a huge improvement. We had initial problems with warping but they were overcome by a more even heating of the knife on both sides. It was a big struggle but we got the toughness to a place where it will chop into steel without actual edge damage, though we couldn't induce rolling or deformation as a failure mode when twisting the blade while in steel. For the actual intended use of these knives though it'll be fine :P
Hardness is quite high, a worn out file won't cut the edge at the belly but a new one will, albeit very slowly. I'm working on organising some paper wheels for a small grinder here to speed up the sharpening while also taking it to the next level.

2: THe normalising step was entirely new to the kamis. As far as performace gains go, i see normalisation as having marginal benefits, but as far as durability goes and the prevention of critical failure from stresses in the steel is concerned I think it's absolutely essential. There's a large rack full of reject knives in one of the rooms here, some of which broke upon testing. Having a look at the grain structure for these knives, it's pretty damn good. not as fine as the milled 52100 but I'd say very reasonable. However there are clearly some flaws going on inside the steel of many of the knives I've seen. I put this down to the fact that they're using scrap spring steel which has already seen a very stressful life building up weaknesses on the bottom of a truck, which the normalisation should help to avoid. As for why the grain is fine, I'd put it down to how weak the coal forges are, with so much heat loss. It means that the grain growth is kept absolutely minimal as the knives are worked at barely a dull red. Very slow moving under the hammer.

3: Answered up top.

4:Saroj is very impressed with the current results and he understands how important it is to ensure that he's delivering high class steel. From a business point of view it puts him well above all the other khukuri houses in terms of performance, even the venerated himalayan imports, who will still use the old methods. However, he has his reservations in that to him the old methods were "fine" with "no complaints" while he sees this as an extra luxury thing. This is something I'm still trying to overcome and as I've said the old method may not have been complained about because people weren't aware of it and didn't blame it for problems with their khukuris.

5: I'd thought about a heat treat furnace, especially due to the trickiness of 52100, however the main issue is electricity usage. Here in nepal, Loadsharing is a fact of life and a pain in the arse. Electricity cannot be relied on to be there when you need it and such machines can't be run by a generator that I know of. We've already had 2 days with no electricity at all here. When this happens he CNC shuts down, the grinders stop, the drills don't work, but there's not a thing in the world which will stop the coal forge kamis from cranking out blades :)

Thanks for the info stormcrow! As far as the canola oil goes, the kamis are pretty excited by the new quench. Once our current oil gets a bit sludgey, we'll be sure to try out canola oil next time to get this whole thing dialed in properly.
The higher durability of our new heat treat steel has really opened up what we can do in terms of grinding here. I know you're not a fan of a lot of the bevels that come on traditional khukuris so it might please you to hear that there's a blade being milled as I type this which has the following features:
25cm blade. Drop point. No recurve. 60mm blade height. aaaaaaand a full flat grind! Should be an absolute ripper

Thanks again! If you've got any more questions shoot them my way.

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Re: Fugglesby at KHHI: Hardening and smashing

Post by nathat » Mon Jul 14, 2014 9:25 am

I have no useful information for you, but I'm enjoying the process. Please continue to keep us updated.

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Re: Fugglesby at KHHI: Hardening and smashing

Post by kyle » Tue Jul 15, 2014 1:17 am

Thanks for sharing!
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Re: Fugglesby at KHHI: Hardening and smashing

Post by Sen » Tue Jul 15, 2014 12:54 pm

I love my KHHI Max and want one of their Bowies next. I really like the idea of them stepping up the heat treat and can't wait to get another knife from them.

Cool vids. Keep them coming.

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Re: Fugglesby at KHHI: Hardening and smashing

Post by Storm Crow » Wed Jul 16, 2014 11:19 pm

Hey, Fugglesby, shoot me an e-mail if you would. Got some more questions/suggestions for you and Saroj.
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Re: Fugglesby at KHHI: Hardening and smashing

Post by Sworbeyegib » Thu Jul 17, 2014 12:14 am

Very cool. Someone on a local forum had just posted a review about the scourge, and kukris have been on my mind lately.
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Re: Fugglesby at KHHI: Hardening and smashing

Post by Fugglesby » Sat Jul 19, 2014 1:09 pm

Sorry for the late replies everyone!
I've been travelling for the last few days so there's been no internet, but honestly this place is soooooo beautiful that you forget it ever existed.
Nathat and kyle, thanks for your support! Sen,the KHHI max was my first khukuri and has a very dear place in my heart :) As for the bowies, there's a few designs on their website that i'm not a fan of but I've had a fair bit of experience with the bowies and give them my full endorsement. The power hammer bowie is an absolute beaaasst of a thing and handles quite nicely. They've just finished up a special run of similar bowies but milled out of a single piece of 20mm thick steel, bolsters and all, they're insane.
Stormcrow, thanks for your enthusiasm! An email has been sent.
Sworbeyegib, thanks for your kind words. Would you happen to be able to find a link to the review? I like to keep track of these things, plus it's always great to hear what people think of your work :)

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