Again, my apologies. I should have checked the proper terminology. I mean the recessed hinge pin(screw) and ,or sleeve ? I am getting ready to have the heat treating and nitre bluing done and that question just occurred to me as I was looking at this blog. Thanks again.

The hinge pin is case colored. Right along with the frame. Installed into it.

Brian, is it customarily removed for the color case-hardening process?





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No. I remove them for polishing but re-install them and set screw timing before coloring.

I heat the nitre salts to 600 degrees and then place the parts to be treated in and watch the color transformation. The parts will go through all the stages of color depending on how long they are in the solution. They have to be carefully watched and removed at the right time to get the correct color for the part being colored.

Perhaps the prettiest color (not right for Parkers) is peacock blue. I use this color on the screws of muzzle loaders and other hardware. The part has to be polished to a bright sheen with 600 grit and then left in the bath longer than the normal Parker nitre blue color.

The bluing salts can be used over and over for years. I use a quarter tank and when I'm finished let the solution harden and then place tin foil over the tank. Nitre salts will draw water from the atmosphere which is not good. The tank has to be covered when not in use. I have to add more salts from time to time when the level goes down from use. But a bucket of salts will last for a long time.

Brighter may be because the part was polished to a finer degree. Highly polished parts (not appropriate for a Parker) results in a brighter nitre finish.

Brian, I sent you a private message.