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Adriaan Gerber

Testing your heat treatment

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How do you test your blades to see if they are correctly hardened and tempered? I want to get better at this. I was testing a cleaver by sharpening and then pressing the edge hard against a piece of brass. If it broke out, it would be too hard. It it bent out and stayed there, too soft. If it bent and returned to place, just right. Then I hammered a piece of 1/4" mild into the edge. It cut the steel but deformed the edge. Too soft. In another place it broke the edge, too hard. Am I on the right track? Specifically chef knives and cleavers. Any help would be appreciated.

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I think the brass rod test you mention first is a fairly well accepted way of testing. A few on here have used a Roxwell tester. Not seen anyone use Vickers or Brinell.

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i would go so far as to cut a nail and expect a little edge deformation, thats for an all purpose user knife made out of 1075. ive got a couple kitchen knives that would lose 1/4" of the edge if i tried to chop a chicken wing so they just get used to figure out how long the edge holds. so edge thickness is a factor, a good knife could fail the brass rod test.

you might want to have a thicker edge on some knives, the brass rod test wont fully work on a thicker convex grind, it could still chip the edge but i have a couple knives which wouldnt flex from a brass rod but still are very nice choppers. 

chopping things or hammering a blade into steel is really extreme and if you dont do it straight you can hurt any steel, i usually just carve a bit of steel, the edge has to stay sharp or else it just wont bite. cutting a nail is more of a destructive test for me, everything i make will be used to carve a little steel though. 

 

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rockwell test machine or calibrated files are important to dial in the temper a brenell might be cheaper and can be accurate enough but makes a larger mark and uses an optical device to give you a reading so its up to a little interpretation base line is if you dont know what your getting out of quench and out of the oven you  dont know if your heat treat is working the tests you have described some can be described as parlor tricks as cutting a nail is more in the technique than the heat treat some give you an idea of what the geometry can do 

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numbers are nice but i prefer results, if a well made knife with a thin enough edge to cut well can cut a nail with little or no damage i think its a bit more than a parlor trick. 

 

that tells me a lot more than a rockwell number, but if youre just shooting for a big number then if doesnt matter if the knife works.

 

basically all i can do with simple steels is watch for the phase change and quench in the right stuff, you cant really mess that up once youve done it a few times, seeing the phase change in the steel is just like seeing a thermometer at 1450F. and a knife thickness piece of 1075 will harden just fine in warm canola or even room temperature canola if its not a thick knife. 

 

i have a hard time believing that you could just sort of mess up and not really know, i have never made a blade that preformed in between good and bad, either the heat treatment works or it doesnt and i try it again. 

 

and dont say "but it could be better". because you really dont know, nobody knows that, and by that logic everyone is making bad knives because they could be better. 

 

big numbers are clickbait. so are super steels. 

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Posted (edited)
15 minutes ago, steven smith said:

big numbers are clickbait. so are super steels. 

This is debatable. I use only carbon steel and it excels at doing what I need, but stuff like m4 or 3v is no marketing gimmick. Though you gotta know how to properly sharpen those steels...

Edited by Joël Mercier

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10 hours ago, Joël Mercier said:

This is debatable. I use only carbon steel and it excels at doing what I need, but stuff like m4 or 3v is no marketing gimmick. Though you gotta know how to properly sharpen those steels...

My Samples include CruWear, S30V, S110V.

Haven't used the latter 2 much but CruWear is impressive, like cutting ribs on the grid with minimal wear impressive....

 

I recently received a facebook message from a maker in Brazil wanting to know about my results with 14C28N.

I reckon I've always had "good" results following Sandvik's recipe, but the last two I used @Garry Keown method with foil and that seems to have worked even better.

Problem is this guy wasn't about "good" or "better" or "seems to", he was quoting Rockwell figures and mentioned a Durometer (which I just googled) so I'm way out of his league......

 

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i have had non normalized Damascus with de-lams make it threw a nail and thats a knife i wouldn't trust to butter bread your mileage may vary you could skip the hardness testers and get a metallurgical micro scope and know even more about whats happening in the heat treat but seams like your not here for help so you do you

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