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Tempering a file knife

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KHalverson:
as quenched if done properly you have created an austenite (very hard and brittle) state in the steel
tempering this properly changes this to Martensite which is  tougher and less brittle .
further tempering @ too high of temp or too long reverts the steel back to pearlite which is soft.
at least that's the technical jargon.
when doing these home home builds  it is better to use simple alloy steels and use the K.i.s.s method
this has been preached to me by a.b.s master and journeyman smiths alike
another thing to take into account is that edge geometry plays a large part in having a good performing knife.
many a knife has been made from files with no further tempering of the blade being done.
now would I take a as hard file and put a full scandi (flat ) grind and expect the edge to hold up under heavy use   NO.
the edge is very likely to chip of worse yet snap the blade.
now take the same file and use an apple seed grind and the edge longevity will be a lot better .
but still susceptible to breakage an be  hard to sharpen.
I prefer a flat grind but leave enough meat at the edge for a slight convex grind
I also would prefer a knife that is soft enough to sharpen relatively easy.
if the edge rolls slightly under heavy use  I can use a steel and strop to bring it back to shaving

Stringman:

--- Quote from: BOWMAN53 on March 26, 2015, 02:34:16 pm ---Tempering releases the stress in steel from quenching. After quenching, the steel is so brittle it can be broken by hand, tempering gives it its toughness back.

--- End quote ---

Yep, got it... Now, how do I apply that to my project. More importantly, is there a specific recipe I can follow - first quench, then temper at ___• for 3 cycles allowing blade to cool slowly overnight between each temper...

I don't have a thermometer so in the past I have relied on metal color to decide when to remove from heat. What's some thoughts from the metal heads.

Stringman:
Thanks Kevan, a post on FB mimics your advise and said,

"If it was never heated past 400°F, you may not want to do anything else to it. That's around the low range of tempering for the types of steel Nicholson used."

So maybe KISS is the right approach with these.

KHalverson:
I get ya now

most files from what I have been told are very close to 1095.
if your quench produces a full hard steel  temper @400 f for 2  2hour cycles that should produce an Rockwell of 58-60 ish which is ideal
I use a grilling thermometer they are pretty cheap @ wally world.
if your unsure of the type of steel that ya have  start @ about the 350 range and temper for 2 hours if the edge is still harder than ya like  up the temp by 25 degrees and retemper  till a sharp file will cut it but not easily
not all steels temper out at the same temp or duration.

BOWMAN53:
Quench in oil, high carbon steels don't really like water. Ruined a few blades recently. Used oil on my current project and got great results.

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