Toaster Oven Tempering Data & Results

J. Keeton

J. Keeton

Joined
Nov 15, 2005
Messages
1,201
So I purchased a duel probe thermometer on amazon for $18 to test out my toaster. Below is how it turned out:

Test Setup:
  • One probe laying on a piece of 3/8'' plate steel
  • One probe laying on the rack
  • Test were run on the "bake" setting @ 400 degrees



Process:
  • Had recorded readings with timestamps from a stop watch
  • Tested the oven without insulation then took it apart and installed KaoWool on top and sides before testing it again
Results:
  • Head to head the plate data showed that the insulated toaster holds at a higher temperature, however, it doesn't seem to get up to that stable temp any faster.
  • With the insulation the plate maintained a temperature of around 433 degrees which was about 15 degrees higher than the rack temperature of 418 degrees. And around 33 degrees higher than the 400 set point. The rack ran about 18 degrees higher than the set point in the insulated set up.
  • It unfortunately took almost 1 hour in the insulated toaster to truly level out at a constant temp... which in the case of the 400 set point test landed at around 433 degrees.

Head to head (plate)


Head to Head (rack)


Full test insulated


Full test insulated (zoomed in to late time data)


Things I found odd:

  • I didn't think the plate would maintain a higher temp than the rack
  • I didn't think the temp would level out 33 degrees higher than the set point!
  • I didn't think the temp would continue to build for over an hour. Every little heating cycle just added some more heat to that plate.
  • I thought the start-up would be much faster once insulated. And the leveling out of the "operating temp."

Final Thoughts:

  • I think I'll be able to use this oven for tempering while having both probes on the plate with the knife.
  • For 1084 I'm targeting 400-420 degrees and should be able to tune this oven on the fly... hopefully determine an appropriate procedure to get consistent results.
  • The oven will require a long time to pre-heat.
    • I may be able to accelerate this by pre-heating it to a higher temp (ie setting it at 450 to ramp up, then bring the dial down to the desired spot)
  • I don't think I'll be able to leave this oven alone for a while; until I get a very good feel for how it runs during a tempering cycle.

What do yall think? Anything stand out?
 
Great data! I did something similar with my little oven not long ago to test the ramp time and stability with different media added for thermal mass. I eventually went with fire bricks above the lower elements and a piece of 1\2" steel on the rack which doubled my ramp time and cut my temp swing by at least 70%
 
Good test, but best is to pick up a cheap PID controller and use that for temp control. I do like your idea of insulating with something. I use a firebrick in oven to help stabilize with PID control. Once at temp with PID control it usually holds within a degree or so of set temp. Asking a toaster oven to temper much above 400°F is a much I think. Good work.
 
Ken beat me to it.

Make up a PID controller in a box with an AC socket on the case ( or buy one already made on Ebay). Plug the toaster oven ( or any heating device) into it and set the toaster control on HI. Set the PID to the desired temp. Note - Place the PID TC where the blade will be, right on the steel plate.
 
Thanks for the suggestions!

  1. Do yall have any specific recommendations on a plug and play PID controler?
  2. The firebricks yall are suggesting are the hard 1'' bricks right? Not the soft bricks?
 
Stacy E. Apelt - Bladesmith said:
This chap makes them and sells on ebay.
He has basic ones that are single setting ( like for a tempering oven) at $140
https://www.ebay.com/itm/Plug-Play-...=item1c3539283c:g:2AYAAOSwdLValbjt:rk:14:pf:0
Click to expand...

I have one from that ebay vendor for my old Paragon. it seems to work ok. Typically the stable temperature is 10 degrees under the set point. The connections seem good, and the switch is solid.

Pro tip: don't put it on top of your kiln and then leave the door open while you are quenching, looking for warps
HttVMQS.jpg
 
I once obsessed over my tempering oven. I often need to temper at 650F, and I stressed a lot, as toaster ovens internal high temp wiring is not rated much over 400F. Thought about salts. Eventually, I had rebuilt my main HTing oven and used leftover parts to build a legit tempering oven complete with pid, tc, SSR, and soft firebrick. It is a nonissue now. The thing goes from room temp to 400/650 and holds 1degree accuracy in just a couple minutes.
 
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