1900 Mainspring

[RalphH]

Greetings,

1075 is very soft and malleable in its annealed state. Cutting, filing, grinding and bending to shape is quite easy. It should be the same shape and dimensions as the original spring. Polish the surfaces that would be on the outside of the flex. You don't want any minute scratches or defects that might contribute to a fracture later. I use 1200 wet-or-dry paper.

I use an electric furnace to heat treat. Mine was made by "Ney". It has a maximum temperature of 2000 degrees, and can be brought to temperature very slowly or quite fast. The temperature gauge is marked in 25 degree increments, and is extremely accurate. I bought it about 30 years ago from Brownells for $300.00.

I place the soft spring in the cold furnace in a small steel pan.
I bring the heat up to 1500 degrees slowly, remove the spring and quench in quenching oil. I turn off the furnace and let cool to 575- 600 degrees with the door slightly ajar. I quickly place the spring back in the oven and shut the door. It cools very slowly with the door shut. I return the following day and remove the spring. If I want it shiny, I polish with 1200 wet-or-dry and buff with Jewelers rouge. Spring is done.

P.S. Brownells still sells the Neycraft 240V furnace, only now it's $750.00.