Into the oven cold or no?

Different ovens call for different approaches. IMO the Evenheat should be soaked for an hour at some temperature above your austenitizing temperature. Use a fast ramp program to get it there and hold it a while. When you open the door and put your work in, it will drop a lot. With some experience it will drop to a temp just a little below your target temp so when you switch to your austenitizing program (with slow ramps) it won't nuke your work with those exposed elements that are inches away. The temperature difference between your cold knife and that hot oven will prevent that little bit of overheat from actually overheating your work, whereas those exposed elements can certainly overheat spots while trying to get the entire oven up to temp. This, in my opinion, is the best approach for this particular oven and its limitations.

It would be lovely to preheat, but you're going to need two ovens to do that and it really doesn't serve much purpose in a knife. Attempting to preheat in a single Evenheat subjects your work to those hot spots while it ramps up and is no bueno.
 
Signalprick said:
Honestly I never heard before this thread that it's OK to skip preheat.
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Just what do you mean by "preheat"?

When I think of preheat I think of stabilizing oven to a set temp, perhaps 1725°F, putting blade in to soak for a specific time (10 minutes perhaps?), removing blade, then ramping oven up to 1975°F allowing it to stabilize, then putting blade in for final aus soak. In this case the 1725°F would be the preheat. Is this anything like you're calling preheat?
 
Ken H> said:
Just what do you mean by "preheat"?

When I think of preheat I think of stabilizing oven to a set temp, perhaps 1725°F, putting blade in to soak for a specific time (10 minutes perhaps?), removing blade, ramping oven up to 1975°F allowing it to stabilize, then putting blade in for final aus soak. In this case the 1725°F would be the preheat. Is this anything like you're calling preheat?
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That's right but I've never removed the parts between the preheat and the ramp up to aus soak.
 
Prequench and preheat are different.

I have heat treated roughly 200 high alloy and 100 low alloy with no preheat and hardness numbers have always been right where they should be. I bring oven to austenitize temp and let sit for 30 minutes then start my heat treat process.
 
It is funny to me that this thread is the first I have read about putting the parts, other than 1084, in at austenitizing temps. I've been doing what Jason described for a year now (in at near data sheet "preheat" temps, preheat, ramp to aus, hold, remove parts and quench). Makes me wonder what other fundamental steps I should be doing differently! You guys all sharpen blades as soon as bevels are ground, right?
 
Sean Yaw said:
It is funny to me that this thread is the first I have read about putting the parts, other than 1084, in at austenitizing temps. I've been doing what Jason described for a year now (in at near data sheet "preheat" temps, preheat, ramp to aus, hold, remove parts and quench). Makes me wonder what other fundamental steps I should be doing differently! You guys all sharpen blades as soon as bevels are ground, right?
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I don’t sharpen a blade until the handle and possible sheath are done, absolutely no reason to handle a sharp blade for the rest of the process.
 
I always TRY to organize my work so I can HT blades in batches. It just makes sense to maximize output after that hour of blazing warm up. To me, that's another solid reason to insert blades at aus temp. They're all done the same.
And I'm not saying guys who start from cold are making bad knives. I honestly don't know the answer to that.
 
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Sean Yaw said:
That was meant as a (clearly poor) joke!
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Actually there is a good reason to sharpen as soon after HT as possible...

Before you get all the hardware etc put on do your edge testing and performance stuff, so if your HT failed you can toss it back in the fire.

Then you just run the edge over the grinder real quick and make it safe.
 
Sean Yaw said:
It is funny to me that this thread is the first I have read about putting the parts, other than 1084, in at austenitizing temps. I've been doing what Jason described for a year now (in at near data sheet "preheat" temps, preheat, ramp to aus, hold, remove parts and quench). Makes me wonder what other fundamental steps I should be doing differently! You guys all sharpen blades as soon as bevels are ground, right?
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I always sharpen the blade before I finish the knife
 
Nathan the Machinist said:
Different ovens call for different approaches. IMO the Evenheat should be soaked for an hour at some temperature above your austenitizing temperature. Use a fast ramp program to get it there and hold it a while. When you open the door and put your work in, it will drop a lot. With some experience it will drop to a temp just a little below your target temp so when you switch to your austenitizing program (with slow ramps) it won't nuke your work with those exposed elements that are inches away. The temperature difference between your cold knife and that hot oven will prevent that little bit of overheat from actually overheating your work, whereas those exposed elements can certainly overheat spots while trying to get the entire oven up to temp. This, in my opinion, is the best approach for this particular oven and its limitations.

It would be lovely to preheat, but you're going to need two ovens to do that and it really doesn't serve much purpose in a knife. Attempting to preheat in a single Evenheat subjects your work to those hot spots while it ramps up and is no bueno.
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I would like to hear your opinion about this .................... https://www.bladeforums.com/threads/thermocouple-position-in-oven.1765879/
 
Lorien said:
would you explain? I don't understand.
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I didn't see this I am sorry! I can only say what I was told by evenheat so don't hold my feet to the fire here but they said that the PID is programmed for each specific oven and resistance of coil and Tprobe, and that if you have a model with the APO (auto power off when door open switch) switch, the PID knows that the oven was opened and will increase wattage as quickly as possible back to set point. If it doesn't have the switch, it will still alarm at a 150F drop in which the PID reads as the door being opened, so it does the same thing and heats as quickly as possible.

It's almost like a "smart" PID. They said that heat soaking bricks and changing temperatures mid cycle is not recommended or necessary. Sorry for the late reply!
 
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