Heat treating of the plane floats finally happened over this weekend. David, my machinist friend, came over and we spend some time getting things setup and running the mini kiln for the first time. This is just one of those things that feels like a fairly major accomplishment.
The mini kiln/furnace was tossed in for free when my wife purchased a rather nice oxy-propane torch a couple years back. Its sat on the shelf, gotten in the way more than once, and moved frequently. Previously David helped fix some of the wiring and we managed to get it to turn on, we heated it up to roughly 1000°F and said it technically worked. It went back on the shelf for well over a year.
There were two issues left to deal with, first was there was no door, a bit of fiber blanket laying around was a simple solution once shoved in the door opening. Last, and probably the largest problem was there seems to be no way to determine the temp, as in the readout is non-functional.
This lead to a long dark rabbit hole, which involved a Netduino and a few other electronic devices with a bit of custom software. Without going into much detail on that, its a device that reads the temp from a thermocouple, and will display it on a computer via a web page. With it I can be at my workbench and monitor the progress of the furnace, yes I have a computer at my main work bench.
We finished hooking up all the electronics, shoved the thermocouple into one of the exhaust ports. We set some charcoal briquettes into the corners. In goes some kiln shelf legs and the plane floats on top of them. We power on the electronics, double check they work, then plug the kiln in and away we go!
It took about an hour for the kiln to get to temp. We monitored the temperature on the computer and once we got close we checked the irons with a magnet every 25ish degrees. Being we were monitoring the temp at the exaust I think we were getting higher readings than we should have needed, but also it was air temp in the kiln not steel temp. So we ended up with readings at about 1640°F at the exhaust, but went off of steel de-magnetism and color of steel to be sure. This all went pretty well, maybe a little longer than I had expected, but still more than acceptable.
One at a time we took them out and dunked them in canola oil. We used a camp style coffee pot filled with canola oil, set in a larger container with water. This served as an inter-cooler, despite the hodge-podge setup, it worked great. We let the steel cool down to about a temperature we could handle, then put them on a cooling rack to let them acclimate to room temp.
We then wiped the oil off and sanded the surfaces shiny once again so we could temper them. We put them in the kitchen oven at 325°F for an hour. I’m not 100% sure we got them hot enough, as we have only the slightest of straw colors, and frankly it was very light, so we may want to do them again with bit higher temp.
Overall, a stellar success, the kiln worked, the temperature read out worked, the oil quenching worked. The next day, David sharpened a few of them and confirmed the still was still quite hard. But for a plane float I want it to keep the edge as long as practical, but still be sharpen able with a file.
Note to self and other budding photographers, you can not hold the camera stable enough to get good photos in a dimly lit space, use the tripod.