My little oven

[chromo]

Built my little oven for small parts, mostly 10"-12" dia. flat plate steel and some other smaller things I make.

If you make anything like this test it safely, I am out in the woods and testing outdoors. Not all microwaves are made the same, my mods are working for me on this one!

I stripped all the inner plastic parts from a non-working Kenmore microwave and also all the controls and workings from inside the shell. This was a large older one. I got it used for $10 at a yard sale and used it for about 6 years myself.
I did not mess with the door windows or latch, these are maybe plastic but worked fine.

After stripping the case out I covered all the holes for vents and where plastic parts had been snapped in place with foil tape. I then used fiberglass batting to insulate the top and sides of the oven part inside the case shell. The latch is plastic but about 1" from the oven wall, I put insulation between them good.
The back of the oven part is a single sheet metal panel on back of case, for this I has some foil back insulation handy, I fluffed it up allot thicker with the batting then used the case screws to hold it in place, just poked the screws through it for now. Should use foil tape or washers etc.. to re-inforce the foil backing around the screws since I the heads can pull through easy.

For heat my first try did not do so well. I found a junk working toaster oven of 1,400watts in my junk pile. I cut a large hole through the top of the toaster oven and the bottom of the microwave and screwed them together, insulated everything well except the toaster side with the temp control. This did not work because the toaster would hit 500F wide open then the controll would shut it off till it cooled. The heat did not rise fast enough into the oven this way and the toaster flipped on and off too much.
My oven got to 280F or a bit more this way. I will use these parts for another oven soon since they work. I need to move the Temp control from the toaster oven wall to the bigger oven wall. I thought I might need to, but was not sure if the highest setting would work as is, but it did not. The 4 tube type elements should work fine, 1,400 watts is plenty of heat for a small oven! I think this oven costs $18 new, mine was on the junk pile.

What I did for now was I found a 240V furnace element in my junk pile. Ni-chrome wire type that looks like a like spring. Since I already had the hole cut in the microwave bottom I just screwed the element bracket to the bottom and made sure none of the ni-chrome wire could touch the case or short. There was 2 sets of coils a short and long element. I wired up the short one to 120V, not enough heat. I cut the long element in half and wired 1 half to the 120V. Still not enough heat. Nice thing about Ni-chrome wire is you can just shorten it to get more heat, shorten it till it glows red if you want, but any more than red hot will just reduce it's life or cause it to break.
So I just tested for heat, shorten one coil, test for heat, shorten other coil, and did this a few times till I got the heat I wanted. I get a nice red glow in some areas of the Ni-Chrome but not all of it turns red hot, though it all produces heat.
My oven is now tuned into a bit over 400F. 4 Bakes today and the hottest part was about 430F checked with a non-contact IR thermometer.
This is plug in and forget, no controls, always on. Being used outdoors!
I will check for the wattage tomorrow with my meter but for today I just ran it allot on a long small outdoor extension cord. The cords never got hot and I never tripped a breaker so I should be in a very safe power level below 1,500watts for sure. My 120V air compressor will over heat that extension cord, so my power draw is a safe level for 120V for sure.

Because the elements are open on bottom right now I sat the oven on a washer drum from the junk pile, the case sits on drum the elements are far away from drum, the drum got around 200F near the top. I WILL enclose the elements and make a flat bottom for the oven soon, was just testing for now and open like this is NOT safe.

I was unsure about the paint and door on the microwave, one reason I tested outdoors and not finished enclosing it yet. I only get a little fumes from the hot paint, and I can see that only the bottom area right near the elements is turning brown from heat. I will strip paint from bottom and test again. The rest should be fine (I THINK), but near the elements of course is the hottest part anywhere!
The plastic latches are doing fine.
The oven door is not glass, not sure the material, maybe like that bakelite cookware or just heavy plastic? It is not melting, not warping, and not getting hazy or anything yet. This is an inner and outer window type door, with 400F parts inside the door read 200F or less all day on the outside.

Total cost of my oven? Almost free! The fiberglass insulation I bought new but was left over from another project so not sure the cost for that. Everything else was free junk you can find being tossed out on side of road for junk man or trash.

Of course I could have tried to calculate the length of Ni-chrome wire I needed for whatever watts, but I had no idea really how many watts I needed for this oven. I just want the oven to heat to 400F and stay pretty close. I will wire in that 3rd element section I have left to a seperate 120V plug and a switch, flip it on to heat up the oven fast then off and let the 2 elements maintain the temps steady.

[CarWiz]

I gotta hand it to ya; you have one heck of a diverse and well stocked junk pile. Glad I'm not the only one that collects parts "I might need someday".

[chromo]

Yes, my junk pile is very diverse.
I do many type of projects, alcohol fuels, veggie oil, hydrogen, wind gennies, etc... I drag home about anything from scrap yards if cheap enough. I have a large pile of DC and AC motors also.

I will probably join that forum for the PA Blaster, I have several old hot water tanks here and several Ideas of my own, might as well see what others are doing with the same type idea.

I just was looking at a junk chest freezer today, looks like a ready made top load blast cabinet to me, cut arm holes and install a window in one side, a baffle and shop vacum other end. Has a good magnetic seal around top.

[nuttyman]

why didn't you just use an old electric kitchen oven? probably a little larger than what you built & you can always find them for free. I have 2 that I found in the local paper for free.

[chromo]

Good question.
As always you can find anything you don't need anytime you don't need it, when you need it you will not find any!

I live in a small rural area, not found an electric stove since I started looking for one, (most use propane around here) and I needed it fairly fast. I go to scrap yards to buy Electric motors and lots of other stuff, they always have a bunch, untill I need one. I been dragging home washers/dryers freezers and a fridges for projects as well as all kinds of tanks, never wanted an electric stove for anything before so about only thing I never dragged home

I went to 2 scrap yards and called 2 others that know me, my scrap yards are empty right now on stoves
They'll probably have a few later this week or next and I will pick them up for about $3-$5 each. I was in a hurry and needed to bake a part to mail out right away though. This will be a handy oven for me to have around, just the right size for the part and does not take up much space, very portable also once I finish it.

[nuttyman]

ooooh. I see them locally every week for free in my local paper or listed on craigslist. I use a small toaster oven as well for small parts. they're great for pop-tarts & jalapeno poppers too!