Heat Treating a New Cast Hammer

In an earlier blog series, I outlined how I built a foundry furnace and cast a replacement hammer for a broken antique shotgun. This is how I heat treated it and fitted that hammer to an antique gun. For the sake of time to keep this a short read, what I didn’t show here is how I sanded and polished the rough casting marks out of the raw casting. In fact, there’s so much to this kind of work I posted only the highlights and left out quite a few of the smaller details. After all, this is not “Metal Casting 101” to teach you how to do this. It’s merely outlining how I do it.

The fresh cast part.

The part is colored in Dykem blue, and the screw hole is marked where it will fit the lock tumbler.

The drilled hole is squared up and fitted to the lock. Shown here beside the original broken hammer. Notice the “ear” for thumb cocking is broken off ?

The heat treat process is done by hand with an oxyacetylene torch, and dipped in Kasenit ferrocyanide.

The part is quenched in oil. At this point the metal is very hard, but also brittle. It could possibly crack or shatter like glass of struck or dropped.

I’ve found that for me, floating the hardened part in a bath of soft lead seems to draw the temper back just right. Too much heat ruins the hardness of the steel. The idea is to have a hard surface to resist battering, but to have a softer core so there’s a little “give” so the part is not brittle any longer.

After putting on a finish, the new hammer is installed and tested. The replacement hammer is shown beside the original broken one.

Another antique shotgun restored to useable condition.