Thanks guys, I have been doing some research. The oil trick has to do with the firing point (not flash point) of oil (the temp of the liquid at which it will flame unassisted). Using this method, temps of 650-700 are obtained, depending on the oil. Old used oil gives a temp much lower (circa 550)> Everything I have read says to quench in oil, not water. Water makes for a higher tensile strength but also higher risk of breakage. Suppose it depends on the steel you are using. I have seen recommended drawing temps for leaf springs from 550 to 800. Dixie says color should be bluegray for their "spring stock". That's about 740 I think. The lead trick is interesting. Apparently, you can vary the melting point quite a bit by playing with the tin/lead mix. 4% melts at 560 deg, 8% at 550. That corresponds to dark purple and full blue, both a little cool for spring tempering. Of course, you can heat the lead to temps much higher than this but you need a pyrometer to know where you are.
