Dave K said:
Jerry, what do you mean by drawing the "tail" to a blue color?
I believe he is suggesting that the area around the frizzen screw should be softened a little more than the upright face of the frizzen.
This increases the toughness of the matrial so it is less likely to break.
Because you want to do this locally, it must be done with something that will heat just the area you want to retemper. I use a small pencil like propane torch who's flame can be directed only at the area I want to effect.
It is a good idea to shield the areas you don't want to retemper. This only requires something to keep the flame from hitting the protected area.
The reference to the color "blue" is a description of the color the metals surface will become.
If you ever took apart a old clock, you may have noticed the spring in it was a rich blue color. That is a good temper for springs and other items that must hard but very tough.
Briefly, when clean steel is heated, the surface changes color depending on how hot it is.
The first color you would see would be yellow, going to straw yellow, then to brown, then purple then blue. Beyond blue, it starts to turn a dull gray.
When heating the metal, care must be made to do it slowly and gently. The colors will appear and start changing fairly rapidly from one to the next. The difference in temperature between yellow and blue is only about 140 degrees F.
If I am doing this color tempering just to obtain a nice blue color for decorative purposes (screw heads look really pretty) I will quench the part in oil when the color is reached. By doing this, the surface has reached the correct temperature but the depth of the heated material may be rather shallow.
If I am tempering the part for strength (as you would be doing here), I just let the part air cool when it reaches the desired color. This allows the heat to penetrate the metal so that the whole area is tempered.