Thursday, May 18, 2017

The E. Marshall Rifle: Case hardening the lock and trigger pieces

This past Friday Jud case hardened all the lock and other small parts of the the Edward Marshall Rifle. This stage of building a hand made traditional rifle is always filled with drama and potential for disaster as are all situations where the parts that are the culmination of months of fine work are put in a bomb containing homemade bone charcoal and baked in the forge for an hour at near welding heat. 

Bad things can happen: the larger parts such as the lock plate can warp, the smaller parts can burn if the temperature is slightly higher than anticipated. All in all I find documenting this stage of Jud's work to be nerve wracking and the results are often a surprise. This time was no exception but … fortunately the parts came thru with beautiful case colors (not intended but always a bonus!) and perfectly hardened, especially the frizzen!

The following sequences of photographs show Jud crushing the bone charcoal that he has made by burning moose and bison bones, sifting the charcoal to achieve the correct fineness of grit, loading the steel "bomb", placing the parts requiring the deepest hardening (the frizzen) at the bottom, tiny parts in a special metal "box" so they won't get lost, and the other parts loaded in, each placed such as to maximize exposure to the bone charcoal.

The forge is then lit and brought up to heat. The box is placed in a steel trough so as not to be disrupted by movement in the forge, and the parts are heated with uniform heat for an hour. Next the bomb is removed from the forge, the lid carefully lifted off and the contents spectacularly dumped into a bucket of water.

The final sequence shows the individual case hardened parts, with their colors - as stated above - not intended but always a bonus!

1. Grinding and pounding the burned bones



2. Sifting the charred animal bone material and adding the parts to the metal box















3. Bringing the forge up to heat and "cooking" the lock parts in bone charcoal












4. The final result