new h/t oven question

V

victoroni

Well-Known Member
just finished reading manual on my first h/t oven - (a new evenheat) no recommendation on when to introduce the blade into the oven.
I assumed one would place blade in oven and proceed with h/t process but now I hear that blade should be placed in oven AFTER desired temp has been achieved - that seems like a potentially dangerous situation ? Need some input from experienced Dogs
 
Disclaimer: I am a rookie so anything I say is questionable.

I do not put my blade in when I turn the over on. I put it in after the over has reached temperature. If I put the blade in there when the over is at room temp, the blade will remain hot for a long time as it gets up to temp (I have the slow 120v version of the evenheat, takes a while to get up to temp)

Here is what works for me:

When the oven is at room temp I put in a scrap piece of steel (used later to heat up the parks 50 quench oil) and turn it on. Run the program for heat treat.

I wait for the oven to get to temp. When temperature is reached the oven alarm goes off. I take out the scrap piece of steel and drop it into my quench oil. Then, I use my long pliers (same ones I use to get the hot blade out for the quench) to put the blade in.

However, the act of opening the door drops the temperature about 200 degrees give or take. So, now it has to get back up to temp with the blade in there before the soak time timer starts. (i usually just re-start my evenheat/rampmaster3 program at that point) Then proceed as per norm.

Hope this helps.
 
I do it pretty much the same as Delta with one difference. I program my first segment to alarm when it reaches a temp just below my target. At that point I quickly remove my scrap and heat the oil. Then I add my knife in the oven. That way when the oven reaches temp I know my knife and the oven should be the same temp and my programmed soak begins. I have no evidence that my way is better or worse its just my way. Make sure you wear heat gloves and glasses, you never know what may happen.
 
I think Chris 'n Delta have summed it up nicely. One problem with putting blade in a cold oven, the blade will be hot for a longer time allowing more time for decarbonizing. Scale "shouldn't" be forming in the HT oven since the blade isn't at temperature to oxidize to form scale, "IF" we're talking high carbon steel.
 
KenH said:
I think Chris 'n Delta have summed it up nicely. One problem with putting blade in a cold oven, the blade will be hot for a longer time allowing more time for decarbonizing. Scale "shouldn't" be forming in the HT oven since the blade isn't at temperature to oxidize to form scale, "IF" we're talking high carbon steel.
Click to expand...
Ken, can stainless steel wrapped in foil be put in a cold oven?
 
Chris Railey said:
I do it pretty much the same as Delta with one difference. I program my first segment to alarm when it reaches a temp just below my target. At that point I quickly remove my scrap and heat the oil. Then I add my knife in the oven. That way when the oven reaches temp I know my knife and the oven should be the same temp and my programmed soak begins. I have no evidence that my way is better or worse its just my way. Make sure you wear heat gloves and glasses, you never know what may happen.
Click to expand...
Hey Chris, how much lower do you set your first alarm compared to your soak temp? Couple hundred degrees?
 
victoroni said:
just finished reading manual on my first h/t oven - (a new evenheat) no recommendation on when to introduce the blade into the oven.
I assumed one would place blade in oven and proceed with h/t process but now I hear that blade should be placed in oven AFTER desired temp has been achieved - that seems like a potentially dangerous situation ? Need some input from experienced Dogs
Click to expand...
It's no more dangerous than when you have to open the oven to take the heated blade out for quenching.

One thing I'll mention: Let your oven get up to set point and soak for at least 30 to 45 minutes before you open the door to put a blade in. This will help ensure that the temperature is a bit more stabilized, and you won't have as wide of a tempurature swing when opening and closing your door. Try to minimize the time that your door is open as much as possible as well.
 
Randy Lucius said:
Ken, can stainless steel wrapped in foil be put in a cold oven?
Click to expand...
Randy, I am NOT anywhere near an expert and can only repeat what other MUCH more knowledgeable folks have told me. It's better not to have the blade exposed to heat any longer than necessary due to the issues with decarb. This was told to me as valid when wrapped in SS foil. Hoss (Devin Thomas) wrote on another forum about using a pre-quench for AEB-L. Even for the oven heating from 1725°F to 1950°F he suggested waiting until oven was at temp before putting blade into oven.

My process for HT'ing AEB-L (Based on Hoss) is to heat oven to 1725°F, allow to stabilize, then put blade (s) into oven for 15 minutes, quench between aluminum plates while oven is ramping to 1975°F, allow oven to stabilize at 1975°F for 15 to 20 minutes. This time prevents quite so much temp drop when putting blades into oven. Soak blades for 20 minutes, plate quench then into deep freeze with blades clamped between two 1/2" (or 1/4") aluminum bars. Then to LN for a few hours still clamped between aluminum bars. I'll usually remove from aluminum bars then double temper, first temper 1 hr, 2nd temper 2 hrs.

Putting blades in freezer at -5F to cool before -325F LN seems less drastic than dunking direct from room temperature to -325F.
 
it is better to wait for the oven to be at temp, as everyone here has said, reasons are it is about time and temperature, so the slowest part of the oven heat up is usually the last bit, so you are actually already at austinitizing temps, before you start your clock, so you are including a variable that is hard to manage... another thing is that your blade is large and flat, and the elements are radiating at fullblast to get to temp, the thermocouple is small and round, depending on a lot of things, this may mean that your temperature in the blde is somewhat different to the tc - because large flat things absorb heat quicker than small round things, but please i think for a well designed oven, this is probably not that important. but for us diy-ers it is probably a different matter, especially for us who didn't get the absolute greatest low thermal mass insulation, and have longer ramp times. Lastly if you do not have variable output controller driving ssr's there may be a substantial overshoot, especially in ovens not designed for knives.

i have to reiterate, this is most applicable to repurposed ovens and ovens not optimised for knives.
 
One thing I did that helped tremendously with my evenheat, I took soft fire brick and put one across the back of my oven to “shield” the element. Then took two pieces of thick steel and aligned them lengthwise with the side elements. They’re away from the inside wall, they help to keep me from jamming anything into the live elements and they hold heat very well. I let me my oven soak for an hour before I use it, the brick and steel hold heat and temp drop when opening the door is smaller than before!
 
Either everyone is super anal or I'm not nearly anal enough...

I put my blades in when I get done wrapping the foil. The oven is usually about 1,000 degrees F, give or take. But I've put the blades in at all kinds of random times and I've never had a problem. I have broken blades and looked at the grain and I can't tell a difference. There has been no real world difference in the end product, either. I'm sure that there is a theoretical effect, and that someone could find a difference in a lab - but in the practicality of actual use I cannot.

Not one of my knives has ever come back because it failed or because it won't hold an edge. I am not a twenty year maker, but my experience does represent a sample size of a couple hundred. That isn't all encompassing, but neither is it insignificant. This number includes hunting knives, folders, utility knives, and a whole lot of super thin kitchen knives that see a whole lot of use.
 
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