Your right to a point, when dealing with low carbon steels the casehardening process adds carbon to a certain depth of the materials surface, the depth of the case is partially dependent on the length of time the part is exposed to the carbon rich environment. Carbon is the essential ingredient in allowing a steel to be hardened. A case hardened low carbon steel component will thus have a very hard exterior surrounding a comparitively softer interior, a desirable trait for many lock components. Traditional tool steels, such as 01 do not require this process, they are already high in carbon and the entire part, not just the surface, will harden with an appropriate heat cycle and a quench. At this state the entire piece is glass hard and just as brittle, it would require tempering (heating to a lower temperture to draw back the hardness and reduce brittleness) In the case of the frizzen above, I would suspect, that since it was made of a high carbon tool steel, it is probably too hard and could shatter without proper tempering. If it was made of mild steel and casehardened it would function fine without having to undergo a tempering operation, though even than it would be desirable to draw the foot back a bit to reduce the chance of breakage, thinner sections can sometimes be completely penetrated by the carbon making them into tool steel, early blister steel was created in a similar process. The case hardened low carbon components can be left much harder than their tool steel equivelents, because they are surrounding a softer steel core that can take increased shock without as much chance of fractures. As for the Springield locks I have no idea, I am positive that the components would have undergone a heat treatment process, though the lock plate would not necessarily have been part of that treatment. If they were tool steel than they would not have been casehardened, but if not they would have been. Without some form of treatement, even the best materials available during the period would have failed miserably within a relatively short period of time. The armorer responsible would probably have been in some deep doo doo. But don't take my word for it, go experiement for yourself, you will probably learn a few things that your materials class didn't adequately explain.
My question is..are there any other parts on the lock that need to be hardened? It is a large Siller lock, came with the kit from Pecatonia.
