Checking Blade hardness

Don Rac

Don Rac

Joined
Oct 3, 2001
Messages
1,191
I don't have anything fancy to use, so is there a way to check the baldes to see what hardness they are, where it begins, etc.? Any answer is appreciated, just want to know how to get to know my khuks down to the last detail.
 
Others will give more complete info in the morning,
but here's some starting info.

Run a file, chakma, or other hardened metal lightly
down the edge and down the side the edge of the blade.
Feel the difference in drag. Less drag (slicker) harder.

The next suggestion is not as difficult as you might first think.
It's also --very-- interesting.

The best way to know exactly where the hardening runs is to
acid etch the blade using common kitchen ingredients.
Takes all of 10 minutes to sit down and see the first signs of
the temper lines.
Vinegar and citric acids diluted with soapy water work fine.
If you want to be more cautious you can limit the treatment
to just the edge of the blade.
The different hardnesses appear as different 'shades'
of frosting or greying of the metal.
Hard is untouched, soft is grey, and the transition zone is frosty.
Has to do with crystalization forms in the metal.

Do a search of this forum for 'etch', 'hamon', 'temper line'
to more complete info.

The temper lines venture halfway across the blade at some points.
 
Hello ddean and thanks for the tip.
A question remains :confused:
Can you polish the etch marks off easily with a metal polish or is the etching more permenant?
 
Pragitam,

If you're interested in the file method, you could do a search on Nicholson, a manufacturer of files held in high regard for hardness. You obviously want to stick with one manufacturer, or better, one file. Doesn't do much good if you use files of various hardness to do the test. Their name comes up in some threads on the topic. May not get everything, but you shouldn't get too many undesired hits like "file" or "hardness" would provide.
 
I don't have too much to say on this. Firkin is telling you straight about the files. If you are going to use one for checking hardness, Nicholson is the only way to go. Use it for nothing else so you know how it will cut. If a store doesn't have this brand I go someplace that does. I won't waist my money on junk.:)
 
Yes. A quick and light etch does not remove very much material, and a run on the buffing wheel with a polishing compound (used an second-stage polish, and my YCS came back up to mirror polish) does the trick. Once you see the coloration changes, stop the etch and rinse the blade with water.

I've used the buffing wheel to take micro scratches out of the edge of my using khuk, and even used it to razor hone & polish the edges of my kardas that had been scraped up a bit (during sharpening by a previous owner, I assume).

Keith
 
I'm merely repeating stuff posted by others who know much, much more about this stuff than I do and have generously shared what they know. I think a post by Yvsa convinced me to try the Nicholson stuff. I'd never paid too much attention to file brands before, just avoided really cheap stuff or used what was provided. Noticed "good" ones and "bad" ones. Now I wouldn't buy anything but Nicholson (unless it was for someone else who would let it rust!), they're worth the extra $ or trouble to find them.
 
Nicholson is the only way to fly.
A brand new flat bastard will almost cut a 60 Rc hardness and will barely cut a 59 Rc hardness with heavy pressure.
By almost cutting I mean it will barely scratch the surface at the edge. At 59 Rc it will barely cut at the edge. Keep the file for testing only and use it sparingly or you will wear the file out for accurately judging hardnesses although even slightly worn out it will still help sharpen 57 Rc and below hardnesses.
Don't use the corner because it will give you false readings.
 
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