Hand Filing Blades - accidental hardening?

D

Dagr

Joined
Jan 25, 2006
Messages
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I have a question for the learned masses - I have just started on my 2nd rough blade, and noticed something interesting. No power tools, just using nicholson files, on annealed 154cm. Those nicholson files cut like I would not have believed possible, friction builds heat. Heat seems to dissipate quickly, but if I go back to file the same area after I've worked it, the action of file on blade gives off a screeching noise (as I've sometimes heard mentioned when testing heat treat?) and it takes a LOT of work to get through what feels like a harder thin layer of steel.

Am I actually getting the steel hot enough by friction for hardening to occur, or am I misinterpreting something else?

Thanks all,
~ Dagr | apprentice noob
 
Have a wire brush handy and clean the file every so often. That will help with a majority of it. I find myself doing it every few strokes. You will find that frequent light brushing will extend the life of the file.

I don't think you're building up enough heat to harden the surface, although I could be wrong - 'cause I aint a knife make'n expert (yet).
 
I think your file might be clogging up. A wire brush or file card will really help with that. Seems to me you would have to file FAST to build up enough heat to harden the surface, but I could be wrong too.
 
Its called 'work hardening'. It happens and, I believe, shallow in depth. Has nothing to do with heat. Mete can verify that or correct me if he sees your thread.

Rlinger
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Thanks rlinger, I'm 100% inexperienced with stainless steels, and haven't experienced that effect with carbon steel. We appreciate your input!
 
I do know that after 154cm is heat and cryo treated (at least by TX knifemakers supply) that my regular files couldn't do much to it- had to use my diamond files. Give the diamond files a try if it is work hardened. Of course, nothing stops my belt grinders...except the breaker tripping.

The only time I have had trouble with work hardening is on bolster or guard material- 304SS and small diameter drill bits. Any pointers other than going slow and keeping 304SS cool to reduce this or take it back down to a less persnikity hardness? A specific heat cycle or something?
 
Now that I think about it, my nickel silver barstock gets harder and harder to drill as I go through it... I don't have the best drill or bits by any means but I sure as heck noticed this....
 
Yes it's work hardening , some steels do it more than others .Very sharp drills, good lube, slow speed but good amount of feed. Anneal steels at ~ 1200 F to soften work hardened areas. ...Persnikety is not a proper metallurgical term.
 
I tend to think it is not work hardening (and as mete said, that has nothing to do with getting warm).
If it was filing fine and then it was making noise and not filing as fast, I would suspect a clogged file. Chalking the file, and cleaning it with a card regularly will avoid some of this. I seems to me it would take a lot more abrasion to create work hardening in 154CM.
Stacy
 
Thanks for the responses guys, I do have a file card that gets used fairly frequently. And I didn't think it was working hardening, because it only happens after I file for a while, and then stop, on restarting I get a hell of a squeel... Oh well, only thing to do is make a few dozen more, and see if I can figure it out;)

~ Dagr
 
I have found something similar when filing O-1. It is always harder to get the file to bite into steel that has sat around for a little while, than it is to continue cutting on a fresh filed surface. I suspected a combination of surface oxidation and oil droplets, either from the atmosphere or skin oil. The heat build up with files has always seemed inconsequential, it never even gets hot enough to sizzle water and only makes it steam if the air is real chilly.

Work hardening of stainless steel is another thing though :confused:
 
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