Kitchen oven tempering

rodriguez7

rodriguez7

Gila wilderness knife works
Joined
Feb 1, 2009
Messages
1,428
so I’ve been using my kitchen oven for a while now, I started with a toaster oven, but the results were to inconsistent. What I’m thinking of trying, not sure if there is any benefit, is putting a couple fire bricks down, laying the blades on the fire bricks, and putting a couple more bricks on top of the blades. Will that help with a more consistent heat? Or am I overthinking this? Thanks
 
I have firebricks in my toaster lining the entire bottom of the toaster. This helps keep more consistent temperatures because the firebricks will hold the heat. I highly recommend it.

I have an external thermocouple monitoring the toaster during a temper, and it fluctuates +10f/-10f degrees continually through the tempers. I let the temper start heating and getting to temp as soon as I start my HT oven. This gives it lots of time to let the heat soak into the bricks.

Don't trust the dials on a toaster oven. My toaster is more than 35f degrees off what the dial is set at.
 
I use my kitchen oven sometimes. Pretty consistent.
I put a cast iron pan on the rack, upside-down and pre-heat. Then put the blades on the pan once temp is reached. Only on Bake, so the (electric) element only heats from below, so the blades are buffered by the pan from direct radiant heat and from fluctuations by its mass.
 
My toaster oven varied to much, my kitchen oven is much more reliable from testing! But I was thinking if I sandwiched the blades in fire bricks, it would just be better.
 
I cut a sheet of JT’s 15n20 to fit the toaster oven. I just put my blades on top of it once it’s equalized in the toaster and use a thermocouple to check along with one of those in-oven thermometers (they’re not as good as a thermocouple, but better than the dial. It holds temp very well, but like was mentioned above the oven dial is off by 20° or so.
 
rodriguez7 said:
My toaster oven varied to much, my kitchen oven is much more reliable from testing! But I was thinking if I sandwiched the blades in fire bricks, it would just be better.
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If you use that toaster oven just for tempering and not in kitchen ...find and install something like this and your problem is solved.............
https://www.ebay.com/itm/WP4451583-...itchen-Aid-Whirlpool-oven-range-/192798147437
lRwKXjC.jpg
 
Josh Rider said:
I cut a sheet of JT’s 15n20 to fit the toaster oven. I just put my blades on top of it once it’s equalized in the toaster and use a thermocouple to check along with one of those in-oven thermometers (they’re not as good as a thermocouple, but better than the dial. It holds temp very well, but like was mentioned above the oven dial is off by 20° or so.
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It is impossible to equalized/have even temperature inside ENTIRE oven without fan . . .
 
I found my kitchen gas oven to be very reliable and accurate using chemical calibration and infrared meters. Within 5 degrees. Much better option than a toaster oven.
 
I prefer my kitchen oven because the knives are further away from the direct source of heat. I also store all my cast iron (four heavy skillets and a big flat griddle) in my kitchen oven, so they work as a thermal reservoir. Cast iron is big and heavy and holds heat well, so there's not much fluctuation in temperature, that's why it works so good for certain kinds of cooking.

Think of a big lake or a full refrigerator. If you go by a big lake in summer or winter, it tends to be cooler or warmer near the lake than further away because the big body of water acts as a thermal reservoir buffering the temperature swings. The same is true of a full refrigerator versus an empty one. All that food that is cold helps keep the fridge cold when you open the door, whereas when you open the door to an empty fridge, it's easy for the heat to "escape".
 
I am in danger of loosing my kitchen oven privileges because I keep leaving my knifemaking only cookie sheet in the oven. When my wife pre heats the oven for real food, she is reminded of that hobby that just keeps on giving.
 
If anyone has "modded out" their toaster oven to be a more reliable tempering oven; I'd love to see some pictures!
 
I just use a small pan of sand in the bottom of mine with a thermocouple to monitor it. so far so good.just let it preheat till the sand is up to temp and let run the cycles.
 
Natlek said:
It is impossible to equalized/have even temperature inside ENTIRE oven without fan . . .
Click to expand...

Yeah, I can see differentials in my shop toaster oven with an infrared AND dial thermometers. It's a bit better in convection mode with the internal fan running. But still, some shielding and thermal mass is helpful. But without going full MacGyver on it, they lose so much heat through the door etc.
 
That’s why I recommend putting a sheet of steel for some thermal mass underneath the blade. It shields it from the heat underneath and with the thermocouple right at where the knife is you can measure and keep a very consistent temperature.
 
A heavy cast iron skillet or a sheet of 1/4" mid steel will help enormously. I don't think a second plate on top of the blade is a good idea. A second plate on the shelf above the blade is fine. Always put the blade in the oven after the oven and sheets of steel have come up to temp. I find that a kitchen oven does fine for HT in the 400-450F range, which is where I temper most all knives. Get a cheap dual probe(or three probe) oven thermometer from Ebay and put the probes on both side of the blade. They even wi-fi to your phone now so you can check on things while in the shop. They cost less than $20.
 
What I did for a while was to load up as much steel in the oven that the racks would hold. I'm talking blocks 3" x 4" x 6" ish, I also put pieces on the floor of the oven to help support bottom rack so i could load up the steel here. i put my knives between pieces of 1/2" angle irons once the oven was up to temp.

Now this took a few hours, mind you, so I'd start this process, then light my forge, usually forger a knife or a few trinkets, then play around with a similar set up to get the interior of my 1/4" steel tube to stabilize at the proper hardening temp and then treat my blades once everything is dialed in. '

I haven't tested my results yet but plan to take a few blades to my buddy who has a really good rockwell tester.
 
This thread is gold. Thanks for the instructable and tips on getting better results out of the ovens!
 
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