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All you metal guys out there.

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KHalverson:
scott
I believe you have your terminology  mixed up.
the second blade looks like a heat treated i.e quenched blade.
temper removes most of the brittleness imparted by quench and a full hard blade.
a sound temper takes time it requires at least 2- 2 hour soaks @ around 400 f for the files.
if u look at the build along again we tempered the blade then used the torch to draw back the spine while annealing the handle
a properly tempered blade placed in a vice will bend 45 deg no problem and spring back straight and not crack.
the A.B.S performance test requires blades to bend 90 deg and no more than the bottom 1/3 of the blade is allowed to crack.
I would be interested in seeing the grain structure on the broken blade.
is it smooth?
or course grain?

the knife in the first pic looks really good.
im glad ur enjoying building knives it can be a ton of fun

Kevin

BarredOwl:
What KHalverson said.

 I think it's called a differential heat treat when you temper or draw the blade spine and handle so that is more like spring steel (blue-purple range) or a little softer  and leave the bottom 1/3 from cutting edge up a little harder (straw color), not completely hard like right after the hardening quench.   

For the spine/handle softening I think some blacksmiths heat a block of steel to red hot and lay the blade on it so the entire cutting edge and tip is hanging out in the air and let the heat (color) soak out towards the cutting edge and tip then removing it before it gets too close to the cutting edge and maybe quenching it to stop the heat from soaking out to the cutting edge.  Haven't done that method myself but I'll bet you can probably find some info on the internet maybe even a video or two. 

HickoryBill:
Yes that blade that broke was to hard/ brittle..Anytime you heat a blade and quench it it hardens it..I usually start out my file knives by annealing them.= Heating them up to nonmatellic and letting them cool down in kitty litter..This cools them slowly.I rough shape my blade blank to desired shape/drill my holes and then harden them..=heat em up to a soft cherry in quench in tranny fluid..then I do my final shaping and polishing..Them they go in the oven at 400 for 3 hours..Letting them cool at room temp..I'm betting it broke at a stress riser..Either in the blade that you couldnt see or one that you created..Files can be finicky tho..and thats just my 2 cents worth...

Stringman:
Thanks for all the feedback. I have been researching this more and finding that this is a whole new world to me. I'm especially interested in the harden/tempering process that leaves a durable resilient edge. I'm still making and having fun with it, but under no delusions about being any good. Just something fun to play with.



This latest blade is an old Swedish file from my grandpas barn floor. It was hardened and then tempered at @400 for a couple hours. After final sanding and polishing, scales of buckeye burl were added. This is my 4th knife that I've finished.







Again, thanks for the advise!

KHalverson:
Scott
don't sell your self short.
you are doing very nice work.
I wish my 4th knife had looked half that good.
another thing that comes into play for a resilient edge is edge geometry.
I find an apple seed grind holds an edge much better for heavy work.
your scandi grinds are very nice but may lack a bit of strength under heavy use.
again nice work .
Kevin

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