hardness testing

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bubbas55

Joined
Dec 19, 2007
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i saw where wayne goddard used what sounded like an ordinary file to make sure his blades are hardened. did i read this right or do i need to fork out the cash for a set of files made specific for this purpose.
thanks
ron
 
I would love to help answer your question, but I'm not so sure what you're asking. I hope this points you in the right direction. After a knife is hardened, the knifemaker will often take a file and run it across the length of the edge to see if the steel indeed hardened like it should. If the knife didn't harden properly, the file will bite into the (relatively) soft steel. However, if the knifemaker did everything right, and the knife is indeed hardened, the file will not bite into the steel, but "skate" off of it. This method will let you know that your steel is harder than it was, but it won't tell you if you got everything you possibly can out of the steel during the heat treat. Files indeed differ in hardness, though, but at least the cheapest files will let you know if the blade hardened well enough.

I sure hope that was what you were asking, and if so, any file will work for this purpose. No pressure applied, really. Just enough to see if it bites in or skates off.
 
I have a set of hardness files and they will give you an idea where you would rockwell. I do have blades of known hardness that I can use for comparison though.
A good sharp file that glides across the edge of a hardened blade is a good indicator that you knife is roughly as hard as the file.
 
Once you get past the decarb, it will seem like the steel is almost soft till you get thru that then it should skate if your hardening worked properly.
 
bubbas55 said:
i saw where wayne goddard used what sounded like an ordinary file to make sure his blades are hardened. did i read this right or do i need to fork out the cash for a set of files made specific for this purpose.
thanks
ron
Click to expand...
Chinese hardness files are like 10$ to 15$. After checking if they are fine, you can use them (in my set 65hrc file is soft).
 
The major problem with the file test is that far too many assume that it tells them the steel was successfully hardened. This is not true. It only tells that the steel MAY be max hard, and is probably hard. The blade could be half pearlite, and the file will skate off of it because it can't cut below what martensite that did form. Unfortunately, there is no cheap easy answer to be really sure.
 
Test blades or strips are always helpful. Use the same steel and same process then when your done you can break that piece and check grain structure if you want. I try to do this when I can. It helps let you determine if your close or way off. Combine that with a file check and it should give you an estimate of where your at. Then do testing on your blades like cutting various materials and what not. If your satisfied with all these then you should feel confident you have made a good blade.


Wanted to add though that there is no replacement for having a decent hardness tester, one of these days Ill have one.
 
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