Oven HT

[W0lfhawk]

Greetings, I am new to this forum an apologize in advance if this is not were I should post this. But my question(s) are,
Do I need to preheat my oven BEFORE I put the knife in for HT? Or can I just set it in there and turn on? Does a farrier rasp Actually need full three-step HT process?
Thank you

 

[A.McPherson]

What kind of oven? A kitchen oven can’t get hot enough to do a proper heat treat. It’ll temper but not get your steel hot enough to harden.

 

[W0lfhawk]

What kind of oven? A kitchen oven can’t get hot enough to do a proper heat treat. It’ll temper but not get your steel hot enough to harden.

What kind of oven? A kitchen oven can’t get hot enough to do a proper heat treat. It’ll temper but not get your steel hot enough to harden.

A modified oven. But I’ve seen guys just set them in and turn it on. I’m just confused as to weather or not to get the oven or what ever you would use, to proper temp before placing the rasp in. My first thought is to have it all staged were you got from quinch, then right into the PRE heated “oven”

 

[weo]

Good morning. Welcome. We need more info. Are you talking about the hardening part or the tempering part of the heat treatment process.
Mr McPherson is referring to the hardening part where the steel needs to get above magnetic (~1450 deg)
Tempering is around 400-450ish +/- (smarter makers correct me as necessary)

If referring to the tempering part, depending on the steel yes or no. Some steels need to start the tempering almost im.ediately, some can tolerate the stresses for longer periods while the oven gets to tempering temps.

Do a search using the custom search In the stickies above and you'll find answers to most of your questions.

as always
peace and love
billyO

 

[W0lfhawk]

Good morning. Welcome. We need more info. Are you talking about the hardening part or the tempering part of the heat treatment process.
Mr McPherson is referring to the hardening part where the steel needs to get above magnetic (~1450 deg)
Tempering is around 400-450ish +/- (smarter makers correct me as necessary)

If referring to the tempering part, depending on the steel yes or no. Some steels need to start the tempering almost im.ediately, some can tolerate the stresses for longer periods while the oven gets to tempering temps.

Do a search using the custom search In the stickies above and you'll find answers to most of your questions.

as always
peace and love
billyO

Okay I follow. So I would ask for answers to both. I am under the impression that a file is already hardened and tempered. So my plan is to skip the anneal process, the hardening process and just doo a temper.

 

[weo]

Heat treating a stock removal blade on an already hardened file is a little above my pay grade, but I'd think that because it is already hardened, all you should need to do is temper it to the proper hardness.

I only do forging of damascus knives (I'm a former blacksmith that got into knifemaking only because I got infatuated with damascus) so I have to the thermal cycling (to reduce grain size), hardening and tempering steps. If you are shaping your rasp knife using a belt grinder, I'd think all you would need to do is temper (350-450 degrees depending on desired final hardness, so your oven would work), then grind, as the final shaping/grinding we who forge do is after the hardening/tempering steps. If you are making the knife using a filing jig and file, then you would need to anneal (soften) the file first and then go through the hardening and tempering steps.

~billyO

 

[milkbaby]

Your farrier's rasp may be case hardened. That means only the outside of it is hardened and the inside is only iron or low carbon steel that doesn't harden enough if at all to make a good knife.

Either grind a short edge and see if there's any edge retention at all as is, or heat treat a piece and see if it will harden. Otherwise you'll have no idea whether this stuff is any good knife material or not.

 

[milkbaby]

OP, see this, post #9 by Mike Turner: Farrier rasp HT question

 

[Stacy E. Apelt - Bladesmith]

OK, from what I read, you are taking a file/rasp and reducing the hardness a bit to make it work as a knife. You will be grinding it hard.
In that case, I would put it in a pre-heated 400-450°F oven and give it two 1 hour temper cycles. There is no quench involved in tempering. You can dunk it in water to cool it down between the temper cycles, but that isn't quenching. Doing this will drop the hardness into the range of a usable knife.

If using a Heat Treatment oven to harden basic carbon steel, the oven is pre-heated to around 1450-1500°F and the blade is put in. Once the oven returns to the set temperature, the blade is soaked for around 10 minutes, removed, and quenched in oil.

 

[joedhiggins]

So, assuming the rasp is actually some low alloy HCS, and not case hardened, temper first, grind second. If you want to test the steel, cut off some bit of the file with an angle grinder. Try drilling the center (as in not through the surface of the file) with a smallish drill bit. If it drills you have a case hardened file. Won't make a knife. Alternatively, you can try grinding off the surface of a small section, torch heating and quenching and seeing if you can break it cleanly or if it deforms.