View Full Version : heat treating oven

03-04-2005, 09:05 PM
Not sure what to do with this one...
It's 110 v and needs a thermocouple for the thermometer and it has no pot for controlling the temp. Maybe I'll cook some brownies...

Hoffman in Warner Robins Ga

03-04-2005, 09:41 PM
Perhaps pizza?

03-04-2005, 09:53 PM
Get a PID temperature controller, a type K thermocouple and a Solid State Relay. You can usually pick up all of these pretty reasonable on eBay. Or I will come pick it up and get it out of your way.

Charles McGough
Sterlington, LA

03-04-2005, 10:20 PM
Thanks charles. Could you give me a breakdown as to what those things do?

03-04-2005, 10:42 PM

Check out this ebay auction:


You buy a thermocouple, and a relay that will support the load. You set that controller at say 1400 deg, it will control the kiln to go to that temperature, but not above.

You can also get some with ramp soak features...this is what I would suggest. You can walk away from it and it will go to temp come down all on it's own.

SSR (transistor) or mechanical RElay? I like relays...when an SSR fails, it almost ALWAYS fails in the on position. I like this because I'm lazy, very seldomly watch the kiln all the way through. They are however loud (click clack) and are prone to mechanical failures. On things that I use a lot, I will use two controllers. One as a "high point kill" (safety) and another that actually controls it. The high point has a mechanical contactor and the rampable has an SSR.

Good Luck,


03-04-2005, 11:30 PM
Do I really need all the electronic doohickies to make it work? I t didn't have all that stuff when it was made. If it was larger maybe I'd consider it.

03-04-2005, 11:38 PM
The PID temperature controller is a digital device that read the temperature from the thermocouple and compares it to a set point(your desired temprature) and turns the heating element on/off as needed to maintain the temperature. The power is switched with the Solid State Relay by the control output of the PID. PID stands for Porportional, Intergrated, Deviation. You can set the PID to the automatic mode and it learns the response time of the device it is controlling and by doing so can control the temerature within very narrow limits. Normally around +/- 0.1Degrees. You sould be able to find a PID, Type K thermocouple rated for around 2300 degrees, and a 40 AMP SSR for around $75.00 on eBay. I use two PID controllers in my homebrew brewery. They do an excellent job on controlling temperature.
IF you decide to go this route email me and I can give you more info.

Charles McGough
Sterlington, LA

03-04-2005, 11:44 PM
I like the 260 in the background. It brings back warm fuzzy feelings from tech school. Back when we actually had to know how to read a meter. All it needs is the roll front case...

Excitable Boy
03-04-2005, 11:57 PM
If it were deeper, I'd entertain making it automated for treating knife blades. I could have used it this afternoon!

It's too small for Pizza.....


Pursue Excellence and the rest will follow.

03-05-2005, 12:14 AM

No, you dont need all the electronics.

However, for the cost of the electronics on Ebay, you really can't go wrong. Getting a variac or a big rheostat will cost you about the same.

Heck, you can probably find a suitable relay out of surplus at work (for a good price I'm sure).


03-05-2005, 10:40 PM
1/4 din PID controller = $150
SSR relay for bumpless on/off $20 ebay..
Type K thermocouple.well.cable $30 ebay..

Same as a $1500 oven then for wax burnout or tempering blades.

Yeah,, I think you can afford to put a nickel in if you can get a dollar out.

Thermocouples? Dissimilar metal joined together by twisting or welding a bead on the two metals, stress trying to seperate the two metals generates a micro-voltage 0-50millivolt is the normal. You can put a meter on it with knowing the mv and actually read the temperature. Pilots during WW2 would take the thermocouples and cables out of crashed bombers, tie them in series like flashlight batteries and parallel groups to gather enough current to operate a radio when they were throwed into a fire. Smart boys..

SSR a electronic relay used to switch loads on and off, main advantage, no spike that comes from contacts opening and closing. Pretty reliable, compact and works well.

PID controller? takes the millivolt input from the thermocouple and "your" setpoint put in keypad and controls the output to the SSR relay turning on and off the element to make it within tolerances..

Heat element? can be just a piece of stainless mig welding wire.. I have seen it done..

If ya ain't gonna use it pass it on.. I got some larger toys here, I don need it.

03-05-2005, 10:54 PM
"1/4 din PID controller = $150"

or on Ebay for 20 - 40 bucks.

As far as elements...I keep stating, buy pottery kiln elements. They aren't that hard to design, if you need help, post a public message. I'll write a tutorial (take a few days)

You can order it and have it delivered for a kiln that small for under 30 bucks. As long as you aren't burning things in the oven, it'll probably last the rest of your lifetime at your temps. My kiln elements last me around 50 firings to 2300 degrees F...much hotter than heat treating.


03-05-2005, 11:24 PM
It's 10" deep. I figure if I put a hundred in it I would have a pretty neat little rig.

03-05-2005, 11:46 PM
Snowman - I would like to cook one of these up myself, and don't want to spend $$$ doing it - so if you could do a writeup, that would be nice; in particullar where to get this stuff cheap (and search terms for ebay, etc). For running it, I only have 220 single phase available, or propane. At the moment, I have no parts, so I will need to start from scratch, with the body of the oven. For stress releving metal, should it be set up with a convection fan, and if so, where should I get it (would a replacement fan for a household oven work, or does it need need to be specialised?) And what kind of tempratures & cycles do you recomend for practical use (I'm working in steel in the 10XX range, sometimes A36 steel, and 6061 aluminum)?

Thanks in advance! http://bbs.homeshopmachinist.net//smile.gif

03-06-2005, 12:03 AM

I am a potter, not a metalurgist...so hopefully someone else will chime in.

What size parts do you want to be able to heat treat?


Bob Quale
03-06-2005, 12:06 AM

I had an oven I put a contol on with an scr for about $125. Look up fuji in a search here, of the bbs, and you will find the how to. The link for the control changed, here it is, call them and tell them what you what to do, they will be able to get you a thermo couple also. I got my fuji control from them. Good customer service!


I have no afiliation with these people, I got the link from a post here.

If I can be of any help contact me.


[This message has been edited by Bob Quale (edited 03-05-2005).]

03-06-2005, 12:24 AM
My Shizouka has a maximum working envlope of about 32x20x6... So I would imagine that's the maximum that I would ever do... Hmm... but it's got a knee, so the parts might be a little thicker sometimes...

OK, so let's say 3 feet by 2 feet, by 1 foot oven internal volume? Does that sound resonable?