Tempering springs to "second blue"

[John Archer]

I recently read in a blacksmithing article about a method of treating springs to what is called a second blue. Apparently it is used on springs that would show on exhibition machines. This is apparently a much richer more brilliant blue than the blue that comes up the first time through the colors. The spring is polished and heated through the colors past blue to grey and then on to the brilliant blue that comes right after the grey.
I haven't heard of this being used in gun building. Just wondering if anyone has done this and would like to hear opinions on whether this procedure would/could make a serviceable frizzen spring.
If you google "second blue spring temper" the article will come right up.

John.

[Acer Saccharum]

the spring has to be tempered to function properly.

My guess is this: thew spring needs a certain heat to be tempered properly. So temper it to that. Then polish it back up again, and bring the heat up until the blue you want is achieved, with the following caveat: As long as the decorative blue comes at a lower heat than the temper blue, you are in good shape.

The colors usually go from purple, to deep blue, light blue, gray.

[Dphariss]

I read some place that steel goes through the color spectrum twice as the heat comes up.
I have heat blued a lot of parts and tempered quite a few springs. I have never seen this.
It runs through the color and blue then fades to silver if it gets this high you loose the color and the temper in a spring.

I temper a lot of springs in molten saltpeter and like this method by it does require care to prevent over heating the thin sections.

Dan

[northmn]

When we discussed this issue before, many dump the springs into molten lead to get the temper needed.  Color tempering is very determinate on eyesight and lighting and can be iffy.  A booklet I have on making springs by Ravensheer (cannot remember the spelling) mentions the method of placing the spring in a small container of moter oil and lighting it.  When burned off it is temepred.  Remember there are three stages to making a spring.  One is the forming and forging, the second is "normalizing" or removing stresses, and the third is the actual tempering.  I would suggest getting Ravensheers booklet on making springs, as it is a small inexpensive handbook.

DP

[Dphariss]

I very seldom have a failure is using blue. Especially the saltpeter bath.
A spring can also be re-arched in many cases by blocking it to the contour and heating to blue.
I have heard many mixed reports in using the motor oil methon. Oil ignites at about the right temp and being at the base to the flame in cooler,  but the flame temp is high enough signifiantly over heat the spring.

Dan

[keweenaw]

To achieve the blue you want, and assuming you don't have a nitre bath, polish the spring to a high gloss after the initial tempering.  Put it on a piece of flat steel and heat from underneath until you get a bright blue.  As soon as it reaches the color (temperature) you want knock it off into some oil or water.  This won't harden it but if you don't it will continue to get hotter from the steel plate.  If it goes to steel gray, you've gone too far and it won't be much of a spring.

[Acer Saccharum]

A spring can also be re-arched in many cases by blocking it to the contour and heating to blue.

Dan, that's a darn handy tid-bit.

[doug]

I have heard many mixed reports in using the motor oil methon. Oil ignites at about the right temp and being at the base to the flame in cooler,  but the flame temp is high enough signifiantly over heat the spring.

     I have made quite a few springs and use the burning oil method.  On large springs like mainsprings, it works well and I prefer it to molten lead.  I broke my first spring in many years, recently using this method but it was a sear spring and small.  I drew the temper on its replacement using molten lead and a thermometer.  I will therefore modify my statement to say that from now on, I will draw the  temper of small springs with molten lead and a thermometer and on mains springs and similar, with burning oil.

cheers Doug

[JCKelly]

What grade of spring steel, and what quench to harden it, are you guys using?
With a good, fast quench O1 tool steel will turn out too hard to be useful even when tempered in lead, motor oil, etc. It would need a good 1000F. If the spring is too hard it can break just while the lock is resting on the bench or in the gun, not being used.

Seems to me the most forgiving spring steel, when one must judge all temperatures by eye, or at least can't reliably temper 900F or higher, is something like 1074, 1070, 1075.

[D. Taylor Sapergia]

I occasionally change the shape of a mainspring or frizzen spring as they have come with a lock, or their replacement.  I heat to cherry red and make the spring the shape I want, then polish it.  Then I heat it in an oxy/acet. flame away from the oxydizing part of the flame - in other words out in the broad part of the flame, to non magnetic red.  To do this I just sit it on a fire brick.  I try to hold the spring at that temp for at least a minute to let it soak at that critical temperature.  I quench the spring in new motor oil - 2 litres.  Then the spring is glass hard, so I carefully repolish it to bright again.  I now draw the temper.  I have a 1/4" thick plate of copper into which I have drilled holes that match the spring's tit.  this allows the spring to lay on its edge with full contact on the copper.  I secure the copper plate in the vise, and heat it from underneath slowly.  I watch for the colours to come through the spring, backing off the torch flame away from the plate as I near the finished brilliant blue.  When the spring is at purple, I usually take the flame away and just watch.  I add a little more heat to let the metal come up to that fabulous blue AND STAY THERE!  I like to let the plate and spring cool by itself, and this allows the spring to cook at the temper heat without fear of going past, ro having molecules in the spring that did not get to the correct temperature, as it might if I flick it off onto the Bench, or quench it.  Commercial lock springs hardened and tempered like this very rarely break.  Our tendency is to not draw the temper far enough.
I have no idea of what steel these springs are made.  And the only thing that I can suggest ab\out a "second blue",  is doing the tempering process twice, because the polished spring only goes through the colour change once, as far as I can see.

[bs2]

After heat treating, and polishing, I use the PIZZA Method.........wrap you spring in foil and cook with a frozen pizza. Turn the oven off and let the spring cool slowly. Remove the next day.  Works well on spring steel and small O-1 parts. I guess you could polish it a second time and re cook!

No-BS

[D Burns]

What Ive used on pocketknife springs and blades should work for you. When they are ready to quench heat them in the forge slowly to just a red heat in a darkened room.take them out.  I point them North till they cool back to black.
Do this 3 times. This stoped all my blade and spring warping. 
NOW slowley bring them up to a red heat till a magnet won't stick to them and quench in  warm moter oil. 
Then for a spring temper I use Ravansher's method of putting them in a shallow tin covered with moter oil and burning in off. I think it's about 700-750F.It will now be a dull grey. Seems to work.
Now it's tempered , if you want it blue , polish the piece and bring it up to about 620F. (melting point of lead?) I use low temp salt. Gives you a bright shiny blue.
Good Luck.
I read somewhere that Sam Hawken used to to some of his rifle furninure this way. Would have been a knockout.