Which blade temperature starts hurting its original tempering?

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kreisler

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May 11, 2012
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i often hear that one should be careful with not over heating the blade (or edge) accidentally when modding the original knife. Because the heat could ruin the tempering of the knife and soften the hardness.

so what are the temperature limits (green, yellow, red zones) as a rule of thumb? or which is the lowest temperature which could already start harming the original knife properties?
 
I cannot help you with a color notation. As my heat treating is done differently. But something around 350*-400* for 30 mins. (less time on a
thin section) will start to compromise the original heat treating. DM
 
When Im modding a knife a try to prevent any color change. Im not sure what temp affect the hardness. I would assume any color change to the blade is going to affect the original heat treat.
 
115Italian said:
prevent any color change. Im not sure what temp affect the hardness
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What 115 italian said. Try to prevent any color change.
Specialy with carbon knives. They first get a light straw color, then a dark straw color. If it get bleu, or next purple, or even light gray, there is a good chance you messed up the temper and thus the hardness on thin parts.
With stainless knives its an different story. They usually temper at higher temperatures. But then again. High heat on a small part of youre blade might do strange things to youre blade...

Go slow. and if you see any color, cool it down with water fast.
 
David Martin said:
350*-400*
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traffic light system "green zone" means "everything is in the safe temperature zone, i.e. below 350*".
which unit is this, Kelvin Fahrenheit Celsius Rankine?

my example is boiling Spyderco's CTS XHP in hot water for 60min:D. will it alter its heat treatment\tempering\hardness?
 
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115Italian said:
When Im modding a knife a try to prevent any color change. Im not sure what temp affect the hardness. I would assume any color change to the blade is going to affect the original heat treat.
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If you see a color change you are too late when it comes to any steel that this matters with.
In other words a light straw color, almost imperceptible, indicates a temperature where the blade is annealing.
 
That said there are blade alloys out there that can take at least 500° F (and much more) with no change in the edge holding ability of the edge. These are the "High Speed Tool Steel" alloys.
Once they are hardened (following the steel maker's hardening protocol) making them soft again is a challenging undertaking.

One example. Break off a high speed tool steel drill bit in a chunk of thick mild steel. Heat the mild steel and the dill bit to red heat and let it cool very slowly with fire brick around it. This would anneal a non high speed alloy a significant amount.

Now try to drill out the broken off drill bit with a fresh new drill bit.
You won't be able to do it.
All that over heating didn't effect the broken bit much did it ? !
 
David Martin David Martin I want to soften the blue loctite of the pivot screw (Techno2 knife) so that i can disassemble this titanium knife more easily. Boiling water 100°C (212°F) should do it! :confused:
 
kreisler said:
David Martin David Martin I want to soften the blue loctite of the pivot screw (Techno2 knife) so that i can disassemble this titanium knife more easily. Boiling water 100°C (212°F) should do it! :confused:
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A little Googling reveals the sad truth :
:( Loctite 29513 Blue 246 High Temperature Medium Strength Thread Locker, 450 degrees F Maximum Temperature, 10 mL Bottle.

The cool guys here whamp the torx screws with a hammer against the end of a torx bit to crush the LocTite before attempting to loosen the fastener ;)
 
Wowbagger said:
A little Googling reveals the sad truth :
:( Loctite 29513 Blue 246 High Temperature Medium Strength Thread Locker, 450 degrees F Maximum Temperature,
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100° Celsius has done the trick for me hooray! I semi-opened the knife (90 degree angled), placed it in a small soup bowl with the blade pointing upwards to the ceiling, and poured in boiling water until the handles were covered with water. After 3min i exchanged the water, poured in fresh boiling water again. After another 4-5min i took the knife out with a towel and right away tried to turn the 3 screws. They came loose right away, success!

Clearly, boiling hot water weakens the blue loctite enough for our purpose. Blue loctite is compromised at that temperature level, that's a fact.

Thanks everyone for your input! This was a real success.
Now i only need to get in my cuscadi custom G10 scale and backspacer for my Techno2 yay!!
 
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