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Homemade knife question, Please Help!

M

melotalk

Joined
Mar 14, 2013
Messages
51
Hi All,

I'm new to the knife world and damn it's amazing!
Just made two small knives using school's machine shop, and hardened them using a homemade charcoal forge (with hair dryer) and quenched with motor oil (It was room temp. oil, I didn't heat the oil first).
It was a lot of fun, but some problem occurred:
The blade was smooth before the heat treat, but it has some weird patterns after quenching.
I didn't know the exact temperature during the heat treat process. I only did the magnet test.


Before heat treating:

Knife #1 with my little Spyderco Dragonfly G10
image.jpeg

Knife #2
image+(1).jpeg

After Heat treating:
image+(3).jpeg

image+(2).jpeg


Any ideas of what happened?
 
Last edited:
you may want to put this in knife making forum they will help you much more there

Its just pitting probably from shocking the steel after cooling it
 
Moved to SHOP TALK, where questions such as this belong and get answered.
 
What you are seeing is decarb, this occurs any time steel is exposed to oxygen while at high temperature. The higher the heat and the longer the exposure, the deeper it will be. This can be accounted for by leaving extra thickness on the blade, which is ground off after the heat treating process. There are also compounds that can be used to coat the blade and keep oxygen from the surface. There are also specialized heat treating setups such a vaccum furnaces or salt baths that are used to heat parts in an oxygen-free environment.
 
Thank you so much Justin! You are right, I did leave the blade in the forge for a while. Thanks!
 
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