The frizzen was heated with an acetylene torch until it was no longer magnetic (and was an orange color). It was then quenched in oil. I then tempered it in an oven at 375 F.
I am now thinking that the oil quench may be the problem and that I need to quench in water. What do you think?
IMHO, a part needs to be heated to a coupla color gradients above non-magnetic to harden properly. Non-magnetic is about 1425-1450, or so. Hardening temp is 1550, for most high carbon steels.
I suggest reheating the frizzen to a higher temp, then quench in light oil. If that doesn't work, reheat and quench in water or brine with about 1/4-3/8" of light oil floating on the water.
If that doesn't work, try the Kasnit, but put the kasnite in a small open top, steel box, just large enough to contain the frizzen, and then some. put the frizzen face down on about 3/8-1/2" of Kasnit and put it in the forge for at least a half hour. IMHO, longer is better, then quench in water with oil floating on the surface.
Temper at 350-375, then remove any scale or discoloration and temper the tail and the pivot, to a blue. Stop heating the tail/pivot before the golden colors run across the pan cover to reach the face of the frizzen.
If you use a kitchen oven to temper the frizzen, be sure to use two good oven thermometers to regulate the temp. The thermostats on kitchen ovens are notoriously innacurate. Some of them are off as much as 100 degrees, so one needs to monitor the oven using an accurate thermometer, in order to accurately temper small parts.
God bless