Making A Mini Electric Forge Fun & Interesting
First, a word of warning: this project deals with mains voltage, and if you have any doubts or concerns about working with it, this project may not be for you. There is a serious risk of shock, fire and possibly death unless all safety precautions are followed. Do not attempt construction of this project unless you are completely confident in your ability to work with mains voltage safely.
Often an idea for an interesting project will come to me from something as mundane and unrelated a task as loading up my truck with garbage to bring to the dump. In with the junk was a pair of cheap heaters that I bought about five years ago to help heat my old shop. They never did work very well, and died entirely about a year ago. They have a fan built in to circulate the air through, and when that stopped working, the heater element would not come on.
Looking at them as scrap, I figured I could do something with the heater element itself. The wire that is used for the element has many purposes, but the one the sprung to mind was a small forge or heat treatment oven.
The main components, the salvaged heater element, the power cord and some fire brick that I had bought last year to build a real heat treatment oven:
The idea was to unwind the heater coil and re-wind it around a form to fit into a small chamber formed by the bricks. The small size of the chamber would be easy to heat up with a lower power element.
Of course, this did not work out the way I planned. The wire on one half of the coil broke in a couple of places while unwinding it, and I had to use the other one. After successfully unwinding that, then winding it around the form, I realized that it would not hold its shape. Indeed, it turned into a real mess and I had to discard it.
So, I was left to either abandon the project, or take apart the other heater and start again with that element. You guessed it, I took the other one apart. This time, I did what I should have done in the first place: use the element without unwinding it.
I had measured the electrical resistance of the whole element and found it to be 40 ohms. At 120 volts, this would provide something like 360 watts of heat and I knew that would probably not be enough. To increase the heat output, I used just half of the coil, and laid that into the chamber:
With just half the resistance and double the power, there is a real possibility that the element would get too hot and burn out before it could get the oven up to temperature.
I did a test to see how well it held up and how hot it made the interior of the oven. I left it running for roughly 10 minutes and it didn’t have any problem heating up an old spade bit to red hot:
To hold the work piece above the element, I drove two screws into the soft fire brick. Since the element is bare wire and is conducting electricity, nothing that’s metal can touch it or it will short circuit.
Encouraged by the good first results, I brought out the high temperature thermocouple and PID that I’d bought for the “real” heat treatment oven. I drilled a 3/8″ hole through the brick to mount the thermocouple at the top of the chamber. I also cut up some other fire brick to block as much of the ends as I could:
I was able to get the drill bit up near forging temperature in about 10 minutes:
At 1515 degrees Fahrenheit, that is the highest I’ve gone so far. I’m not sure how high it will go, but there is the risk of the element wire itself melting, and the would be the limiting factor. As shown above, I did some pounding on the red hot bit to mark my first ever real attempt at forging steel.
Here’s a video on the build: