How To Methods to find out if your blade is tempered or not?

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APS89

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Apr 21, 2023
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How do you find whether your blades are tempered or partial water/oil Quenched?

Thanks
 
An etch in FC would probably show the temper line if it was a partial quench. A file on the edge would show if it is untempered or inadequately tempered.
 
The file method is just using a file to see if the teeth of the file "bite" the steel of the blade. An untempered blade will be so hard the file will skate over the blade without biting. This steel is very hard, so hard it will sometimes break when dropped. You temper the blade to relieve the blade from induced stress from hardening. Tempering it will reduce hardness but enhance ductility
 
Jim malone said:
The file method is just using a file to see if the teeth of the file "bite" the steel of the blade. An untempered blade will be so hard the file will skate over the blade without biting. This steel is very hard, so hard it will sometimes break when dropped. You temper the blade to relieve the blade from induced stress from hardening. Tempering it will reduce hardness but enhance ductility
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I thought tempering the metal made it more hard
 
APS89 said:
I thought tempering the metal made it more hard
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In the US, tempering usually refers to the final part of the heat treating process, wherein the steel has been hardened, but is then re-heated at much lower temps to soften it slightly to make it less brittle. In other parts of the world such as the British Isles, the word, temper, is used to describe the entire heat treatment process.
 
polish avenger said:
Time for you to get this book View attachment 2709527
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J. Hoffman said:
Do some reading on Knife Steel Nerds. It will explain a lot.
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fitzo said:
In the US, tempering usually refers to the final part of the heat treating process, wherein the steel has been hardened, but is then re-heated at much lower temps to soften it slightly to make it less brittle. In other parts of the world such as the British Isles, the word, temper, is used to describe the entire heat treatment process.
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Can you type the easiest method to find out whether the edge of a Khukuri is water quenched or not?

Thanks.
 
Yes.....but you won't like it.
The easiest way is to ask the person who made it.
Other than that, telling for certain whether it was quenched in water, oil, or microwaved butter is pure guesswork.
Do you know what steel was used?
Is there a visible hamon?
 
polish avenger said:
Yes.....but you won't like it.
The easiest way is to ask the person who made it.
Other than that, telling for certain whether it was quenched in water, oil, or microwaved butter is pure guesswork.
Do you know what steel was used?
Is there a visible hamon?
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They told me it's water quenched (only the edge).

They use 5160 steel or car leaf spring
 
Like Stacy said...a file is your friend. Sandpaper will also bite harder into the spine than it will the edge if the edge has been quenched.
 
polish avenger said:
Like Stacy said...a file is your friend. Sandpaper will also bite harder into the spine than it will the edge if the edge has been quenched.
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I have to rub a file against the edge, if the file leaves bite / scratch marks, it isn't quenched right?
 
IMG-20241113-WA0002.jpg


I guess this isn't quenched right?
 
I know it is hard to grasp for a person who is not a smith. The metallurgy of hardening and tempering is complex, and testing it requires special equipment do really know.
Once a blade is hardened, tempered, shaped, sanded, handle put on, and sharpened it may be impossible to know the methods used.

I'll try and explain a few things.

First - I don't see how a khukuri could be edge quenched. It is curved and water is flat????? If the maker said it is water quenched edge only I would doubt any other information they give. Many khukuri makers use second use steels like car and truck springs. This is not necessarily bad, but they rarely know exactly what the steel is. Their methods of hardening and tempering can be pretty primitive and uncontrolled as well. This isn't a problem for most people as it allows easy resharpening. Plus, most folks who own a Khukuri don't actually use it for much cutting.
If the seller was a known maker and has a good reputation, I would trust what he said to be reasonably accurate. That said, many overseas sellers blend a lot of hype and fiction into their specs. Some makers use descriptions of methods or specifications that make sense to them buy may read wrong to a person from a different country. For instance, they may say in their language, "Water quenched with edge only hard". That may be read or translated by someone as "edge quenched in water with a hard edge only."

1) Hardening the blade is done by quenching. The blade is heated to around 1500°F/815°C and then quickly cooled in a quenchant. The quenchant can be water/brine, oil, or air. Quenching method and quenchant choice are mainly determined by the steel choice. As mentioned above, not knowing the steel type can lead to doing a generic quench. This may harden it somewhat, but the results can vary a lot. Most quench methods harden the entire blade. Blades with very thick spines, like a khukuri, will have a softer spine than the edge (read on).
2) Tempering is done to the hardened blade to relieve the stress of the quench and make the blade tougher. This lowers the hardness. Tempering is a structural change in te arrangement of the atoms. It lowers hardness and increases toughness. A khukuri has a very thick spine that holds a lot of heat, and when quenched to harden the blade the spine may retain the heat long enough to not harden, or only partially harden. Because of the steel type and the spine thickness, a water quench is usually used. It is actually a brine solution, not just water. Additionally, the heat retained in the spine may bleed down to the thin edge and do what is called auto-tempering.

Testing for hardness immediately after quench or after tempering is often done by taking a file and filing along the edge at an angle of around 30°. Do it like you were trying to sharpen the blade with the file. I use what is called a second file, which is between a bastard file and a finishing file.
If the file slides along the edge easily and makes a high-pitched sound (called skating), that indicates the edge was hardened. If the file digs in a bit and makes a duller sound, but does not remove much or any metal, it indicates the edge is a little less hard. It may be from a less than perfect quench, or because the blade has already been tempered to a lower hardness. Testing the spine can show a differential hardness due to blade geometry or selective tempering with a torch.
If the file digs in and easily removes metal like a plain bar of unhardened steel, it is not properly hardened, or never was unhardened.

I hope this helps you.
BTW, Welcome to Shop Talk. Fill out your profile so we know where you live a d a bit about you. It helps us give clearer answers.
 
sharpen the edge so its shaving sharp, and then chop a pine 2x4 in half twice. if its still sharp its been hardened. if the edge is curled or folded over its not hardened. if it chips its been hardened but not tempered.
 
Your video shows the file biting into the steel. All that tells you is the steel is softer than the file. A decent file is hardened and then tempered to ~64HRC+. The edge on that Kukri may be 57HRC, which isn't bad at all for such a knife and its application.

What John said above is excellent advice.
 
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