arilar,
In re-reading a few of these posts, I realized that it appears that paulvallandigham is assuming that your frizzen is made of modern high carbon steel.
The instructions he gave are for hardening and tempering modern high carbon steel. Those instructions do not work on antique parts made of wrought iron or mild steel, since those materials do not contain enough carbon to harden and temper using the method he described.
Case harding, by heating the part packed in carbon, or using modern case hardening compounds are the only way to harden wrought iron, or mild steel parts.
paulvallandigham is correct that case harding CAN create a hard surface that is only a few thousands of an inch deep, however, the longer the part is "baked" in the hardening compound, the deeper the case hardening.
The method described in my last post is the same method used by blacksmiths to make blister steel of wrought iron. In the production of blister steel, the carbon penetrates the full thickness of iron, making it as hardenable as any modern high carbon steel. The only difference in procedure of case hardening and blister steel production is that blister steel is "baked" in the carbon rich environment for a much longer time.
I seriously doubt that your frizzen is made of blister steel, as the process to produce blister steel is, and was, VERY time consuming, and therefore very expensive.
Case hardening is much less time consuming and therefore much less expensive, and far more attractive to a government supplying large numbers of firearms to a large army.
Anyone interested in learing about blister steel should find plenty of information on the net.
J.D.
