I have successfully cast a new knob for my heater, so I thought I would show you you how it is done. It is not hard and it only takes about an hour of work. It takes about 8 hours for the rubber to cure so the entire process will take about 24 hours. The resin hardens in 5 minutes, so once the mold is made you can make parts quickly.
http://moldingheaterknob.blogspot.com/
