Sharpening a friend's fire ruined Leek.

N

n7titan

Joined
Jun 14, 2014
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On my recommendation, a friend picked up a Leek a fair bit ago and he loves it. But apparently he played with it more than I knew because when he lent it to me for sharpening I noticed how soft the tip was.
I mean, the last mm or so of the tip bent over fairly easily when I used it to pry open some plastic snaps. (the clear front casing of a plastic compass)
It forms a burr super readily; 3M 30micron polishing paper on wood will leave one if I use too much pressure. Surprising considering I'm pretty much stropping at that stage.

He said he heated the blade once to melt some rope-ends or something. :barf: That's probably what caused all this, isn't it?
 
Yes; probably. Every alloy / heat treatment has a critical temperature that when exceeded will effect the temper and hardness. Some are surprisingly low; My company makes gears for the aerospace industry that are carburized (Case Hardened) to a 60 - 63 Rockwell range; Depending on the alloy; once hardened any stress relieve or embrittlement bake can not exceed 310° to 375° F or it will draw the hardness down.
 
Uhh yeah... any part of the blade that got hot enough to melt rope is definitely ruined. Tell him he needs a new knife and inform him what heat treatment is so he can prevent doing something like this again.
 
I would think that it would have ruined the temper, making the steel harder/more-brittle. So it should have snapped not bent.
 
KennyB said:
I would think that it would have ruined the temper, making the steel harder/more-brittle. So it should have snapped not bent.
Click to expand...

No. Generally speaking, the higher the temper temperature the lower the final hardness. When that blade is taken hotter than the original temper, the hardness will decrease making it softer.
 
KennyB said:
I would think that it would have ruined the temper, making the steel harder/more-brittle. So it should have snapped not bent.
Click to expand...

If he had immediately quenched it after heating it this would be the case. But letting it cool down slowly will anneal it. Its how (basically, although the process is more involved) knife makers soften most steels to work it prior to heat treat. This is all dependent on the temp it got to.
 
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No, he could quench it all he wanted. If the steel wasn't at critical temperature (past red hot) when quenched, quenching it will do nothing but cool the blade.

Ah, you must have edited your post as I was typing mine.
 
Thought so, I'll tell him the bad news and how heat treating works when I give it back.
The knife is well used though, I can't knock him for enjoying it. At least it wasn't something pricier.
 
eKretz said:
No, he could quench it all he wanted. If the steel wasn't at critical temperature (past red hot) when quenched, quenching it will do nothing but cool the blade.

Ah, you must have edited your post as I was typing mine.
Click to expand...

Yeah must have. I thought about it after I typed that and considered he probably didnt heat it to austentize with whatever he was using. Maybe on the very thinnest part of the edge.
 
Yeah that screwed with the HT. best bet is to contact kershaw's warranty and see i about changing the blade, i think its around $10 not sure though.
 
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