I make 5 to 10 springs a year, mostly V shaped mainsprings. I forge them to approximate thickness out of 3/8" drill rod, and after final shaping etc, heat red hot and quench in water. My current method of drawing the temper is to immerse them in old lube oil in a small tin tray and supported by a couple of 1 1/2" finishing nails. I heat the oil, with a torch until it catches fire and let the oil burn away.
I am not really sure why the burning oil method works, because the flames are hotter than the temperature that I am drawing to, but the method works and works well.
I used to float the springs on molten lead in an electric lead pot with first a small thin piece of iron to measure colour and later with a lead thermometer and heat to 680 degrees F. The colour spectrum was the beginning of grey just beyond dark blue.
cheers Doug
