The tempering toaster thread

JG Custom Metal Works

JG Custom Metal Works

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Nov 27, 2013
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I'm making this thread to see how others have their toaster ovens setup for tempering. There are other threads on here with detailed descriptions on how to setup a PID/thermocouple and I'm going to include links to those at the bottom of the thread. That appears to be THE way to go.

With that being said, I've read that some folks have had luck just adding "thermal mass" to the oven and using a thermometer to track the temperature real time. I have fire brick and am going to try to test this out latter today or tomorrow. I'd prefer not having to buy/wire a PID if possible but, as with most of this kind of stuff, I probably will once it's all said and done.

Has anyone here figured out a reliable way to reach/maintain accurate temperatures for tempering cycles? If so, what methods did you use and how did you test for accuracy? Please share pictures or details of how you have your oven hooked up.


Here are two GREAT threads on PID conversion by two VERY informed gentlemen.

http://www.bladeforums.com/forums/s...Pid-Toaster-Oven-Conversion?highlight=toaster

http://www.bladeforums.com/forums/s...tempering-with-toaster-oven?highlight=toaster
 
A low budget thing I did was shove some blocks of aluminum in the toaster and use a kitchen thermometer. This is about the most basic setup I can imagine, and it would work pretty well for someone starting out. The PID, thermocouple, and insulation are great ideas.
 
I have a couple firebricks coming up to temp in mine now. Anyone have any luck using a infrared thermometer to gauge temp in these things?
 
I put a PID controller in a $10 toaster oven from a garage sale. It was super easy. I haven't actually tempered anything since I did it though.

The main downside to the toaster oven is its size. Though maybe there's a way to bolt a couple together side by side to do a longer blade :).
 
You are right that thermal mass is a good way to help control a toaster oven used for tempering. However, fire bricks are not good thermal mass. They are refractory made to insulate. Steel and aluminum are great thermal mass. Placing a plate of 1/4" or 1/2" thick steel on the shelf will allow much more even temperature control. Don't make the plate the size of the rack, though. Leave at least 1" of space around the plate for convection. The best setup would be two 1/4" plates of steel with the blade between them. Place the probe of an oven thermometer between the plates next to the knife blade. That would read the real blade temp accurately. Very accurate oven thermometers with probes can be bought for $10 now days.


A PID controller will make the whole process much more accurate.

Bring the toaster oven up to temperature and hold for a short while before placing the blade in the oven.

A kitchen oven is far better if available.

Toaster ovens are not designed to regulate temperature ... just to get hot. They also are not designed to be hot for an hour or longer. They will work sort of OK at best, and for small blades only. I would say half the rack length is about the max blade length.
 
Stacy E. Apelt - Bladesmith said:
You are right that thermal mass is a good way to help control a toaster oven used for tempering. However, fire bricks are not good thermal mass. They are refractory made to insulate. Steel and aluminum are great thermal mass. Placing a plate of 1/4" or 1/2" thick steel on the shelf will allow much more even temperature control. Don't make the plate the size of the rack, though. Leave at least 1" of space around the plate for convection. The best setup would be two 1/4" plates of steel with the blade between them. Place the probe of an oven thermometer between the plates next to the knife blade. That would read the real blade temp accurately. Very accurate oven thermometers with probes can be bought for $10 now days.


A PID controller will make the whole process much more accurate.

Bring the toaster oven up to temperature and hold for a short while before placing the blade in the oven.

A kitchen oven is far better if available.

Toaster ovens are not designed to regulate temperature ... just to get hot. They also are not designed to be hot for an hour or longer. They will work sort of OK at best, and for small blades only. I would say half the rack length is about the max blade length.
Click to expand...

As always, thanks a bunch Stacy.

I can do the 1/4in steel trick. Do you think it would be a good idea to do that with a regular kitchen oven too?

I can probably use my kitchen oven to temper as long as the McMaster-Carr quench oil doesn't contaminate it or stink up the house too much. Obviously I'll clean what I can off of the blade before putting it in there. I'm just wondering if the oil gets soaked into the steel at all during the quench? If so I'd hate to have it vaporize out into the oven and have the next casserole coming out tasting like motor oil.

Anyone use their kitchen oven for tempering in conjunction with non-organic quench oils? Do you have any tricks for eliminating all the quench oil from the knife before putting it in the oven?
 
I use my kitchen oven to temper my knives. All I do is wipe the blade down with a rag and spray it with brake cleaner. It works well for me and doesn't make the oven/house smell at all.
 
Wipe of the blade well after HT, take it in the kitchen and wash it well with hot water and Dawn...then put in the pre-heated oven at 400F. Take out after 1 hour, rinse with cold tap water to cool down, dry...and put back for a second one hour temper. Cool off in water again after the second temper.
 
Unless you have a badly regulated or very old oven, it isn't really a necessity. Some folks place a sheet of steel in just to have a smooth and flat surface for the blade to sit on as well as to even out any heat differentials. I don't use one, but my gas oven stays pretty much on temp.

If you have an electric oven, a 1/4" plate of steel on a shelf a few inches above the blade and a plate on the shelf with the blade on it may be a good idea to cut down radiant energy.
 
I installed a PID to my toaster before I decided to start sending blades off for HT.
I now use it for kydex and it will hold the temp to within .5 degrees very easily.
 
A few things I have discovered while playing around and tempering with my toaster oven:
-I initially couldn't get it to hit 400, I shielded the heat sensor with Al foil and can now get up to 500.
-toaster ovens don't produce constant heat, they run in cycles. I found that even though my thermometer registered 400 (an average), The knives were experiencing higher temps as a result of being directly exposed to the heating elements during the cycling. now I put a sheet of Al foil below and above the knives to protect them from the direct radiant heat. And keep the thermometer under the foil "tent" as well. It seems to have solved the problem.
-I use a tray of sand as a heat sink
 
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