Kitchen oven tempering

I like to verify that the oven temp is actually what it's supposed to be every so often by using 2 different thermometers.

I also use one of my wife's huge stone cookware thingys to act as a heat sink, and highly recommend doing so. Cast iron skillets, anything to help mitigate temp swings.
 
The best method I have seen is to bury the blade in a tray of dry sand (if using the domestic oven, it is worth investing in washed- and kiln-dried play sand). A TM902C pyrometer is a good investment. It costs under 5 bucks delivered and will display temperature from a typeK thermocouple in degC only. It comes with a glass-fiber-insulated thin bead probe, 3ft long, that is thin enough and flexible enough to close in the oven door. The probe is good to about 400 degC, 750 degF. Bury the probe in the sand next to the blade, feed the cable through the door seal and read the blade temperature during tempering.

Do not use a TM902C above 800 degC (1472 degF) unless you have checked its calibration: I have access to a calibrator and have found that some are fine all the way to 1372 degC (2500 degF) and others are accurate to 800 degC, but will deviate from the true temperature once it gets above 800 degC. It is not easy to tell the difference without a calibrator.
 
Stacy E. Apelt - Bladesmith said:
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.
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Would you place the blades on top of the plate?
 
I'd just like to add for all those using their kitchens oven to temper. CLEAN the hell out of those blades, and when you think it's fully clean, do it some more! we breath in enough bad stuff as is. don't need to be eating it too or worse serving it to others.
 
"...Would you place the blades on top of the plate? …"

No, I like to defy gravity and put them on the bottom of the plate. ;)

OK, I had to do that. Yes, just set the blade in the pan or on the plate, and set the TCs next to it.
 
C’mon man, I said that a couple times in this thread. I guess you need to be a moderator for anyone to believe you in here lol.
 
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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good use of nice steel :rolleyes:
 
Josh Rider said:
C’mon man, I said that a couple times in this thread. I guess you need to be a moderator for anyone to believe you in here lol.
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Never even saw your comment!! But ya, I’ll believe Stacy over you! Ha ha!! Thanks.
 
A gas BBQ grill would be a very poor tempering oven. It would work, but you couldn't get an exact predictable result.
 
Stacy E. Apelt - Bladesmith said:
A gas BBQ grill would be a very poor tempering oven. It would work, but you couldn't get an exact predictable result.
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It has a decent hood on it to keep the heat in, but i will take your word for it thanks Stacy. :)

EDIT-But please let me know if this might indeed work well. :)


milkbaby said:
Planning to use with or without wood chips? :D
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Ha ha without! :)
 
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A BBQ grill has no insulation, and heat would be very irregular. Opening it would dump all the heat , so you would be trying to heat the void back up again after placing in the blades. Also, the gauge on a BBQ is VERY inaccurate. It may vary by 50-75 degrees, and only reads the temp at the top of the hood. The temp at the grates would be very different.

For tempering you need an insulated box with a het source. A toaster oven will work on the minimal side, and they can be converted by adding some insulation and PID control to do small knives pretty well ( see PID Controlled toaster oven in the stickys). A kitchen oven with a digital meat thermometer by the blade can be set to get pretty good tempering control.

I suppose a crafty guy or gal could take the bottom of a BBQ grill and add a insulated top with an end door to insert the blades, a circulation fan for more even heat, a PID control for the burners, etc. … but it would be an expensive task to get a fairly poor tempering oven. ( and you couldn't cook a steak on it anymore) I bet most folks could get a small used oven ( gas or electric) for little or nothing and have it in the shop to use for tempering only. This would allow putting in steel plates on the shelves for thermal mass, and adding some TCs and readouts to keep track of the temperature of the blade.
 
Stacy E. Apelt - Bladesmith said:
A BBQ grill has no insulation, and heat would be very irregular. Opening it would dump all the heat , so you would be trying to heat the void back up again after placing in the blades. Also, the gauge on a BBQ is VERY inaccurate. It may vary by 50-75 degrees, and only reads the temp at the top of the hood. The temp at the grates would be very different.

Ah fair enough. :)

For tempering you need an insulated box with a het source. A toaster oven will work on the minimal side, and they can be converted by adding some insulation and PID control to do small knives pretty well ( see PID Controlled toaster oven in the stickys). A kitchen oven with a digital meat thermometer by the blade can be set to get pretty good tempering control.

Will check those stickys! :)

I suppose a crafty guy or gal could take the bottom of a BBQ grill and add a insulated top with an end door to insert the blades, a circulation fan for more even heat, a PID control for the burners, etc. … but it would be an expensive task to get a fairly poor tempering oven. ( and you couldn't cook a steak on it anymore) I bet most folks could get a small used oven ( gas or electric) for little or nothing and have it in the shop to use for tempering only. This would allow putting in steel plates on the shelves for thermal mass, and adding some TCs and readouts to keep track of the temperature of the blade.
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I think i'll look for a small used oven eventually, but will use the one in the kitchen for now, thanks for your time Stacy really appreciate it. :)
 
About 10 years back, I was at a large "Whole Church" yard sale. There was a bit of everything. On fellow had a no-heat cooktop (Interference type) and an in-the-wall convection oven with digital controls ... both were new-in-box. The cooktop was not of any interest to me, but I considered the oven for the shop as a dedicated tempering and other low heat purposes oven. He wanted $200 for it ... about 25 cents on the dollar. I walked around the rest of the tables and came back to look at the oven again .... it was gone. I am still kicking myself 10 years later over that lapse of judgement.
 
I have a "curtain" of 4 layers of tinfoil forming a kind of muffle around my blades in a little toaster oven. I put that in after reading here about some concern about some parts of the blades being in close proximity to the heating elements and that made sense.

I also have my unfinished blades of shame in the bottom of it for thermal mass. So.....there is a lot of extra thermal mass in there :D
 
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