Beefing up a toaster oven

R

Randy3000

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Jun 3, 2017
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I am rebuilding my heat treating oven, and thought it would be nice to have a separate tempering oven. I need the temperibg oven to reach 675 degrees. I read where a lot of guys rebuild toaster ovens for solder reflow, and figure if it melts lead solder i should be able to make use of one. The toaster oven i have on hand is 1300watt. My plan is to tear the electronics out and totally replace with pid and relay. I guess it isnt much different than building my heat treating oven. Main thing i am worried about is even heat distribution. I guess i could line the door with something. Anyone done this?

Edit
Ultimately, the oven i built here in this thread didnt work out. I highly recommend not using roxul, especially at 650 degrees, even though it is rated to supposedly handle higher temps.
 
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I will take the shell off and see how much room i got to work with. It would be pretty awesome if i can get all the controls to fit in the current electronic compartment. I dont know about putting isowool on the door since it is exposed, what is a good fire resistant, nontoxic, fairly thin insulation?
 
Add thermal mass to even out temperature swings

Add a barrier to guard the blade from overheat with radiant heat.


Both achieved with steel plates as heavy as you like, between elements and blade steel
= a muffle.
 
This toaster has elements on top and bottom, and has 3 racks. So i can fit a sheet metal guard on top and bottom and put blades on the center. I took the shell off and it measures 3/4" deep, so i figure 1/2" insulation would be good. I saw the ceramic store has 2'x2'x1/2" durablanket for $15.

The oven is 8" tall, 16" wide, and 10" deep. So i can cut a 10"x2' strip and do one side and the top, then take the leftover 14"x2' and cut into 3 pieces 14"x8" and do the back, door, and stuff the electronic box with the last piece.

I guess i will make my actual electronic box build off of the current one.

EDIT
I still dont like the idea of ceramic wool, i read many threads where people complain about the dust and lungs hurting or a cough after a single firing. I did find this stuff and think i will use it instead
https://www.foundryservice.com/prod...-wool-board-1-2-and-1-thick-x-48-x-96-sheets/
 
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Alright, i got everything i need to make this happen.

Toaster oven from Aldi.
Q0D1H3c.jpg


It has 4 elements, two top and two bottom. It says 1300 watts on the outside. The top knob has modes Broil, Bake, Toast, and Off. Measuring resistance through the power cord live and neutral reveals

Toast 12 ohms
Bake 21 ohms
Broil 24.5 ohms
Off infinite ohms (no continuity)

I have been using this toaster oven to temper. I usually used Bake at 400 degrees. Guess how hot it actually gets????

9VuOL7C.jpg


An even 600 degrees!!! Now i know why my heat treating hasnt been optimal, the tempering has been my issue!!!

Good news is, this thing can already hit 600 degrees without any additional insulation. Although i have some extra firbrick laying around, and i will be cutting it and using refactory cement to secure it in between the oven shells.

I plan on keeping the timer in tact and the mode knob, so i can adjust the resistance if i want, although i think Bake mode will work just fine. I will be bypassing the temp knob. Basically i will cut the input and output wire to and from the temp knob, then run black wires off them to the terminals on the ssr. I currently dont have anything hooked up to those ssr terminals right now, i am just using my box to check temp, since i always curious about it.

Here is a better view of the control box so far.
wVwT0AF.jpg


It is pretty simple, the switch just gives the pid power. I plan on using the mode knob on the toaster to cut off power to the elements if i want. You may be thinking i have the thermocouple wires swapped on the pid, but i assure you i dont. In fact, i hooked them up wrong since i am used to yellow being positive and the temp started diving into the negatives.
 
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Here is how the toaster wired
2ncxuIN.jpg


The thick red wire coming from the power cord is the hot wire. It goes to the timer/bell and coming out is a thick white wire and a skinny blue wire going to the light. The white wire goes into the temp knob disconnector, which doesnt work for crap on this model, and out comes a blue wire going into the mode knob. Coming out of the mode knob is a white and black wire, white wire goes to the top front element and black wire goes to the bottom front element.

So all i have to do is cut the white and blue wires at the temp knob and connect them to my ssr and i should good to go.
 
Ground? We dont need no stinkin' ground! This must have been built on a monday.

9Ewzkyq.jpg


Got it wired up. Got the thermocouple going through the back so i dont have any holes in the element shields i will put in later. I didnt forget the ground. I did, however, run out of connectors, so i just have the ground gator clipped to the power cord for now.

PzXLQdd.jpg


It is basically impossible to photograph the pid display and get all the digits to line up. But the thing works. Time for lunch, then i will do the element
FSu7xfX.jpg
shields and insulate.
 
Great build or rebuild. Very neat workmanship! Congrats.

I did pretty much the same thing on a old toaster oven I found at a used thrift shop. Rather simple and worked great. Then our very expensive Breville convention oven quit working because of the digital controls. I thought great I'll just rebuild this with the advantage of convection.
Now I like to think of myself as a better than average handy man. My dad always told me "if some guy could put it together I could figure out how to take it apart". Well I'm here to tell you I have no idea how they assemble that oven. After two tries I did finally get it working. I blame the first failure might have had something to do with the two beers I had before I started. With a clear head I still couldn't get it completely apart but could get at enough components to make it a working tempering oven. Just a FYI I wouldn't recommend anyone to try this with a Breville convection oven without a fresh box of bandaids and a ice cold six pack to congratulate yourself at the END of it or for the disappointment that might be a possibility ! LOL
 
I took a microwave apart and took off the transformers and diodes and resisters and capacitors and all that stuff off the circuit board. I tried using the transformer, thought i had figured out how to wire it up, and soon as i plugged it in it blew! I bought a 120vac to 12 vac transformer built a bridge rectifier with the diodes and a capacitor filter. I can etch metal and mark with it now.

That microwave was complicated, i can see how a convection oven with digital display and circuit board could be equally complicated.
 
I used some refactory cement to cement some firebrick pieces to the oven.
kr9WJfU.jpg


I let the top and bottom dry, then i did the back. I let it dry for another hour and then test fired it. The back pieces popped off but the top and bottom set up well and are stuck tight. The cement said an hour set time and then you can fire set it, but it needs a few hours before firing.
 
That looks interesting, is it like pvc cement? The silicon stays flexible a little, is that stuff more rigid?

I am not sure what to do about cementing brick to the sides since the panels have several indentions pressed in them. I do have some scrap sheet metal. I may tac weld some pieces on and then cement bricks to the flat metal.
 
This isnt really working out like i expected. It seems adding firebrick to the sides where the controls are is making it hotter on the control side, and i have growing safety concerns. The exterior also gets extremely hot at 600 degrees and it will burn the crap of you if you touch it. Ordinary wiring is not supposed to get that hot. It kind of freaks me out i used to run this thing in my house all the time while i was outside working.

I am going to tear it apart and make a new oven using 1" roxul insulation, and run bare wire off the element ends through the roxul and make connection outside. I paid a lot of money for my house to risk it.

Edit
I just bought a 2' x 4' piece of roxul for $12 including shipping. The peace of mind is well worth it.
 
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Weld-On #4 is a solvent glue. Add (wick/pour) some into the joint, hold the joint together for 1-2 minutes and it's stuck. Minimal to no clamping needed as the joint chemically fuses. You need a respirator (because it's nasty) for Weld-On #4 but the speed and accuracy of your acrylic builds will be much better. Weld-on #16 is functionally model airplane glue. I only use it for waterproof acrylic builds.

I don't recommend using Weld-On #3. It's even faster than #4, but respirators cannot effectively filter the fumes, so you will end up with tingly lips for an hour or two after you use it.

Hope that helps!
 
BTW, try some 1/2"-1" inswool between the walls of your toaster and the elements. It might help with your overheating issue. Also, consider getting two pieces of 3" x 0.5" thick x 12" mild steel and temper your blades between them. It'll help to flatten warps and maintain more stable temperatures for the blade.
 
That was some fast shipping!
S48rzBf.jpg


I placed the roxul between the inner hull and the wiring, figured if i trapped the wiring the wires would heat up more. This way, the vents in the outer hull, and the metal itself, can dissipate heat better.

jxBMcAq.jpg


It is 1" thick and the space i am putting it in is 3/4" to 7/8". I cut reliefs in the roxul anywhere there was a protrusion out of the inner hull. I know insulation is not supposed to be squeezed, but it actually was pretty effortless getting the outer hull back on.
NINxsUW.jpg


It has been at 350 for awhile and i can lay my hand on the oven and it is warm, but it wont burn me unlike before. The control side is cooler than the top.

I did have to cut the door spring. I need to rig up something to keep the door closed. I also will put more roxul on the other exposed surfaces, but i wanted to test this out before i started cutting up all my roxul.
 
I put a fan blowing on the outside and it is cool as a cucumber at 450!

Edit
Just hit 650 and with a fan on it, i feel pretty safe. Going to finish insulating it and then get a smaller desk fan instead of the big box fan. The box fan cools it a little too well.
 
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I got tired just looking at all that ! :eek: I just put a piece of ceramic floor tile in mine . :D
 
I completely rebuilt my main austenizing oven and then immediately started the tempering oven. It will be good to get back to knifemaking!
 
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