Who measures hardness?

I see in the HI descriptions of various blades a number for Rockwell C hardness, and noticed that they often seem quite high for such large blades. Also, given the pictures I've seen of the factory, I just wonder if the kamis test hardness there with an instrument, or maybe calibrated files, or whether that's done in Reno. And is it done for every blade or just spotchecked from time to time. I'm just curious.
 
Bill Martino

Bill Martino

Joined
Mar 5, 1999
Messages
34,096
The kamis have never heard of Rc but judge the blades for hardness with files. They call hardness "pine" and they have several levels of "pine." They are shooting for an Rc of about 58 but can miss a point or two in either direction.

We usually check every blade here, too. I have a 12 or 15 year old finishing file I use that is very familiar to me and it tells me pretty close. DanK, Yvsa and I compared our file tests and they came within 1 Rc. I have taught Vikash to check the blades with my file and if they are below 54 or 55 we set them aside and take another look.

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Blessings from the computer shack in Reno.

Uncle Bill
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Hey Rusty, do you think this is a thread for the Kama Sutra oil?
wink.gif
Sorry, couldn't resist--got a bit O' the demon in me lately >:

Rob
 
It would be too high for a large chopping knife if the whole blade were that hardness -- they're edge-quenched so only the edge is that hard.



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-Cougar Allen :{)
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This post is not merely the author's opinions; it is the trrrrrruth. This post is intended to cause dissension and unrest and upset people, and ultimately drive them mad. Please do not misinterpret my intentions in posting this.
 
Experience tells me that there is nobody who can tell exact HRc hardness just by using a file. I test my carbon steel blades after quenching with a fresh, new file to see if they are very hard (file skates off), but would not try to judge HRc on a tempered, finished blade this way. I have access to either a mechanical as well as an electronic HRc tester and know that most of the results acquired by using a file are just shot and often 2 to 4 HRc points off the reality.

But besides that i think that every experienced bladesmith (and it is hard to find some being more experienced than the kamis) can make a decent, well hardened blade without having a HRc tester available.

Achim

http://albums.photopoint.com/j/AlbumList?u=575309
 
With the equipment i have available i may test HRc hardness from as close as 1 mm (1/24") to the edge.

Achim
 
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