Polishing, temperlines, and other secrets of the khukuri revealed!

tallwingedgoat

tallwingedgoat

Joined
Jan 13, 1999
Messages
1,422
I wanted to bring out the hardening line of my 18" AK to give it a "Japanese look". There are several differences between a khukuri and a katana. 1) The khukuri is made of 5160 steel, not iron sand. 2) Khukuris are edge-quenched, not clay hardened.

This means the khukuri's hardening line (hamon) won't look as good. But it's still there.

I used ferric chloride to etch the blade, and 1500 to 2000 grit sand paper to reveal the hamon. my efforts are so far unsuccessful. The hamon disapears once I polish it.
frown.gif


But the acid etch showed me exactly which part of the blade is hardened. When the blade is bathed in acid, it turns gray. But the hardened area becomes pitch black.

Far as I can see, the hardened area is 8.5" long on this 12.5" blade. The boundary is well defined and straight. It starts 2" from the cho, and stops 1.5" from the tip. The hardened zone tapers at both ends and is generally as wide as the primary bevel (0.5"). The width is fairly consitant, with the widest point at 0.7" located 3" from the cho.

Another way to look at this is that only the straight edge of the blade is hardened. The curved parts (the tip and the "neck") is not.

The hamon is very different than that found on a Japanese sword. Which extends into the ricasso and swallows the tip with an upturn.

Basically what this means on the khukuri is that a very small part of the blade is hardened to 58 HRC. The entire tip and "neck" (the areas that receive most stress) is probably the same hardeness as the spine.

This is part of why the khukuri's tip don't break during digging, and the blade don't break during prying.

[This message has been edited by tallwingedgoat (edited 14 October 1999).]
 
Uncle Bill,

Can you tell me how the kamis polish the blade and handle in Nepal? I have no power tools, and if I can bring a khukuri to that level of shine, I'll be really happy.
 
Thats really intresting information. Its amazing what you learn on the H.I. forum. Thanks Goat.

What acid, concentration, and temperature was used in the acid bath?

Looking at how the kami's harden the khukuri, it makes sense that the transition in hardness is so well defined. It looks like they really know what they are doing!

This will be an interesting test on the khukuri's that were too hard at the tang. Are there any around that have not been repaired?

Will


[This message has been edited by Will Kwan (edited 14 October 1999).]
 
It was ferric chloride (Radio Shack PC board etchant), dilluted 1 part per 4 parts water at room temperature.
 
:
Goat I etched the little chakma I made with a solution of apple cider vinegar and some lemon and lime juice I used to clean my Keris with.
It didn't leave quite so much residue as it seems you might have gotten with the ferritic acid.
It had a nice line,but like you say it was no where what the Katanas have.

My wife had one of those cheap aluminium throw-away roasting pans like you cook a turkey in.I was able to carefully fold it up a tad and flatten the little raised spots on the bottom and soaked the Keris in that for about 4 days total.That way it didn't take so much solution.
I don't think it bothered the Keris that much with the nickle content it has.It may not take as long on a Khukuri.


------------------
>>>>---¥vsa---->®
Cornbread ain't s'possed ta be sweet!....Dagnabit gurl,whut did they teach you way up north in....;) hehehe.

Khukuri FAQ


 
No!This is not educational!Acid in aluminum?Cliff warned me about this.I thought that the members would have enough sense to look it up.Cliff was right.I was wrong.

------------------
 
:
ghost.I know better than to put strong acid in auminium or anything else except glass.
I sincerly hope everyone else does too.

------------------
>>>>---¥vsa---->®
Cornbread ain't s'possed ta be sweet!....Dagnabit gurl,whut did they teach you way up north in....;) hehehe.

Khukuri FAQ


 
Luckily I have some plastic buckets available. Aluminum would not do. But then again Yvsa was using apple cider, so it's not an issue.

When working with Ferric Chloride, make sure you get some latex gloves. Otherwise try to remember all those lessons from high school chem lab.
wink.gif
 
For anyone else thinking about doing this. I personally don't think the hamon on the kukuri is worth the effort to bring it out. The kamis never intended it for cosmetic purposes. And it's one thing to etch out the line, but to keep it after the polishing is a real pain in the a$$. But it was a fun exercise.

Make sure you cover the brass and handles with tape. Packaging tape worked well for me.

Something I didn't do but should have was to tape the whole blade, leaving only an inch width of edge exposed to the acid. This would save you lots of time repolishing the whole blade. And believe me, with only sandpaper, the best I can manage is a satin finish, not the mirror polish the kamis are capable of.



[This message has been edited by tallwingedgoat (edited 15 October 1999).]
 
:
Goat.I have used increasingly finer papers to hand polish to a better than satin polish.Afer 800 grit wet or dry used dry and worn out I would go to Crocus Cloth.After that you can use jewelers rouge on a flannel cloth.If your finish wasn't to messed up with the ferritic acid then it shouldn't take that much.
If you even had a hand drill it would help.Then at least you could use some buffing pads with compound on them to polish it out.
Of course if you are around a town of any size you coul find a chrome shop that might polish it out for not too much money.


------------------
>>>>---¥vsa---->®
Cornbread ain't s'possed ta be sweet!....Dagnabit gurl,whut did they teach you way up north in....;) hehehe.

Khukuri FAQ


 
You guys stay away from anything far from PH 7,or at least read the directions.Base is just as Haz Mat as acid.I have never seen a kami put anything resembling a mirror finish on anything.
 
Goat,

If you want to keep the temper line.Don't go higher than 600 grit with sand paper. Higher than 600 grit, you'll have to use water stones( not ordinary ones) to bring out the temper line again. Keep the direction of sanding parallel with the temper line.

You can buff the spine to shine, or selectively sand it to a higher grit and burnish it to good shininess.

Joe
 
Goat, many thanks for the very interesting information. I am not at all surprised by your results. This is exactly how a high quality khukuri should be hardened.

Here is how we polish the blade in shop 2 and to the best of my knowledge we are the only shop in Nepal to use this method. The khukuri is polished using a power grinder with buffing wheel. They start with some heavier grit compound on the buffing wheel and get the blade into condition for final finish. The kamis then change the buffing wheel and then they make use of the "magic" stone. The kamis pulverize the "magic" stone into fine dust, use some wax on the buffing wheel, run the wax across the magic stone. The wax, of course, picks up the hand crafted grit, and then the final finish.

Handle is also polished on buffing wheel using the same procedure.

Again, thanks for great information.

------------------
Uncle Bill
Himalayan Imports Website
http://members.aol.com/himimp/index.html


[This message has been edited by Bill Martino (edited 15 October 1999).]
 
You must log in or register to reply here.
Back
Top