Ignorance is not bliss!

S

Steven F

Joined
Oct 12, 1999
Messages
1,237
I must confess that I actually know little about knives. I got into khukuris because of a news article I came across about a year ago that mentioned the Gorkhas in East Timor. I started looking into the Gorkhas and the knives they carried, and this eventually led me to the HI site. Once there, I got hooked -- in part because of Uncle Bill's incredible trust ("Don't send any money, I'll send the khukuri, and if you like it, then send the money. If you don't like it, just return the knife.") and also because of the forum. Everyone seemed so knowledgeable and willing to share information.

So here goes -- I know from being a part of the forum for a while, that it's apparently possible to gauge the hardness of a blade by running a file across it. But what I don't know, and what I'd appreciate someone explaining, is how, using this technique, a person is able to be so precise as to determine a 57 from a 60 on the hardness scale. I guess what I'm really asking for is some practical guidelines that I can understand and use. Thanks for any help that anyone can offer.
 
You can buy sets of files that are tested and marked for hardness testing. If a file marked RC60 "bites" a piece of steel it is softer than that. I don't have a tool catalog at home, and we have had a Rockwell tester as long as I have been working so I don't know specifics about how accurite they are but I know they are out there. My guess is that Mr. Martino has a file of known hardness and gauges from that.
 
Hi Steve,
First, don't run a file perpendicular to the edge!!!! (I know someone that did that). Run the file as if you were using a stone and pushing the file from back to edge, diagonally.

Reading the results is more art than science. It varies from file to file and the amount of pressure. What we are watching is the amount of "bite" or lack there of (skating) at a given pressure. As the hardness gets closer to the hardness of the file it becomes more difficult to guess.

How do you learn this esoteric art? First, buy a smaller mill file (6-8inches)NEW. After you gain some experience you will be able to do the testing with almost any file....your brain is an amazing computer and be able to compute the file and its condition along with the other variables.

Next, buy some inexpensive knives of knowen hardness. Any knife will work to learn with if you don't mind scratches. Get some that are softer,Rc54-55(this by the way isn't considered soft); some a little harder, Rc57-59 and then some in the Rc60-61 area of hardness. And a piece of dead soft mild steel that will have about .3%carbon and run around Rc20. Test and compare the feel you get between them after awhile you will start to get the hang of it.
smile.gif

Dan

[This message has been edited by Dan K (edited 09-04-2000).]
 
Thanks, guys, I really appreciate the help! I'll be doing as you both suggested. Ron, I'm going to search for a set of test files as you suggested, and, Dan, I'm heading to the local hardware store to pick up a small file after which I'll start by practicing on the knives around the house. It'll be a while before I'm brave enough to try it on my khuks! Again, thanks a bunch!
smile.gif
 
:
Steven be sure and get a file handle to go with your file. A file can be used without one, but my grandfather taught me that a file without a handle was like a knife without one. Doubly dangerous and awkward.

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>>>>---¥vsa---->®

"There's no trick in being a humorist when you have the whole government working for you."

...............Will Rogers......

Khukuri FAQ
 
Stephen,
You can also do this with a butcher's steel. Same method, just less chance of damage to the blade. I can tell just by sliding the steel along the edge where the harder sections are, and how hard one knife is, in relation to another. As far as actual RC goes, I'm clueless, but for my purposes, I can definitely tell if a blade has been hardened enough, and in the correct places just by how my steel feels as I run it along a blade. Let us know if you can find files that are of specific hardnesses, I'd like to get some!

Regards,

Rob

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The only thing better than a sharp knife is... Lots of sharp knives! :)
 
Those who have visited Uncle Bill's Cantina have seen the ancient little finishing file with a khukuri handle that I use for Rc estimating. It is so worn that sometimes I need to check several times to make sure I am using it at a place where it is not worn too badly. Yvsa, Dan and I would come with a point when testing for hardness which does not say we were right but at least if we were wrong we agreed about it!

Thanks for good tips. I learned by testing known Rc.

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Blessings from the computer shack in Reno.

Uncle Bill
Himalayan Imports Website
Khukuri FAQ
Himalayan Imports Archives (18,000+ posts)
 
I like to use a small chain saw file. These are made to use on really tough metal, and cut like bejasus. The other great thing is that (at least here in Maine, where wood-cutting is next to godliness, you can pick up a 'standard' good-quality cs file at any hardware outlet.
Just let it 'skate' over the edge, as if honing it. If it bites readily, RC is less than 55. Slight bite, 55-plus. Little or no bite, pushing 60's. IMO, the tool you use isn't as important as the experience and feel of the operator.

Ken

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The sword cannot cut itself, the eye cannot see itself.
 
Thanks everyone! I truly appreciate all the tips, but what I appreciate most is knowing that I am a part of a very special group of guys -- the HIKV Krewe! Thanks again, gang!
 
Bill and Yvsa and a lot of us knife knuts have filed and ground and honed a lot of blades (and often other steel tools) and noticed how it felt and sounded and looked. If you want to guess Rockwell number with a file you'll have to file blades of known Rockwell to build up a database to compare to, and even then you could be off some because the Rockwell test doesn't measure quite the same quality of steel that filing does. Two blades of the same steel tempered to the same Rockwell number will file the same, but different steels can have different abrasion resistance when tempered to the same Rockwell. The Rockwell test measures resistance to indentation by pressing a diamond pyramid into the blade with measured force and measuring the indentation it makes -- and resistance to indentation isn't the same as resistance to abrasion.

The Rockwell number isn't really what you want to know, though. What you want to know is how this blade will perform in use compared to other blades you've used -- and filed. You can get an quick idea of how it'll perform by trying a file on it -- and although it's not a perfect predictor, with a little experience it's probably as good or better a performance predictor as the Rockwell test.

You don't need to spend fifty years at it to get useful results -- just take a file and try it on some knives that you're familiar with and pay attention to how it feels and sounds and looks. While you're at it you might try it on any other tempered steel tools you happen to have around and don't mind file marks on. Try it on some mild steel, too, just so you'll know what that acts like, and try filing the smooth part of one file with another so you'll know what full-hard steel feels like.

The real trick is holding your tongue just right -- like this.
tongue.gif


-Cougar :{)

P.S. I had to edit this post because I didn't hold my tongue just right the first try ... didn't want to mislead anyone....

:{)


[This message has been edited by Cougar Allen (edited 09-05-2000).]
 
OK, Steven, that's enough for lesson one.
Tomorrow Uncle Bill can explain how to distinguish steel composition through the taste test. I heard this one once, but if you haven't, ya gotta ask Uncle about it.
 
Thanks again, gang, for all the tips. Now, it's just a matter of practicing. Speaking of which, you should have seen the look on my wife's face when she walked into the house and saw me sitting on the floor, file in hand, with all her precious kitchen knives and my various pocket knives spread out in front of me. I think she's really starting to worry about me and this knife thing. I tried explaining HIKV, but she was unable to understand the seriousness of it. Women!!!
biggrin.gif
 
There's been some discussion of those special hardness testing files in the Shop Talk forum here. Seems most of the knifemakers who've tried them don't like them -- the softer files in the set wear out rapidly and if you keep buying new sets that runs into money, and you still have to use your judgement. The general opinion seems to be since you have to learn how to hold your tongue right anyway you might as well just use an ordinary file.
tongue.gif


-Cougar :{)
 
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