And Chambers says to NEVER quench any of our frizzens in water - they will crack and break! They must be quenched in oil. We hang our frizzens on a wire hook (coat hangers work fine) and heat the frizzen face until it turns a cherry red color. This color temperature will require an acetylene torch, a single mapp gas and propane torch will just not get it to a high enough temperature. We heat it until it hits the bright cherry red and then immediately quench it in the oil swirling it in the pot until it quits smoking and then leaving it in the oil to cool completely. If this is a round faced lock with a very large frizzen we concentrate on keeping the majority of the striking surface at the red color, the portion of the face above where the flint strikes does not require the constant attention that the the spark bearing portion does. Once it's cooled we draw it back in the kitchen oven at 375 for an hour, turning off the oven after an hour and letting the frizzen cool with the oven.
Here are our official Heat Treating instructions:
HOME HEAT TREATING THAT WORKS
The term “heat treat” refers to two operations: first to harden (heat and quench), and second to temper (soften) to a useful hardness. The tool steels used in our locks will harden clear through when quenched (immersed) in oil alone, therefore water should not be used to quench since it can cause cracks to occur.
HARDENING
The most successful hardening equipment is some sort of open flame such as acetylene torch, forge, or propane torch (MAPP gas sold at Sears produces more heat than propane). When using propane or MAPP gas two or more torches are needed for parts as large as the frizzen.
An electric furnace is not suitable for hardening since it has no flame and too little oxygen. It can remove carbon leaving a soft surface, but it is excellent for tempering since it does not adversely affect carbon at these lower temperatures.
Twist each part on the end of short lengths of wire (so it can be hand held and quenched easily) and heat it uniformly to a bright red (1500 degrees) then quickly immerse it in a quart or two of light motor oil. Move it around in the oil for about 30 seconds, then leave it in the oil to cool. It should harden on the first try, but if not successful the same procedure can be used again. Success means too hard to file.
TEMPERING
Hardened parts have to be softened to a useful hardness by heating to specified temperatures. This can best be done with a furnace with a temperature indicator, or next best with a kitchen stove.
Another method that requires a little more skill, is by color. The part must be polished and then placed on a half inch of sand in a container such as a large jar lid. When heated slowly on the eye of a kitchen stove, in good light, colors can be seen in stages from straw, then tan, brown, purple, blue, gray. Parts should be removed from the heat when the following appear, in order of their appearance:
FRIZZEN: pale yellow (375 deg. RC 62-64)
SEAR, TUMBLER, FLY: full blue with some fading into gray (600 deg. RC 54-56)
