heat treating

[gunnut41]

I lost my computer and have just recently got one up and running.
There was a post about tempering main springs that I had a copy of that I cannot find to copy to my computer. Does anyone know the author?
Had to do with a can with oil in it set on fire!
Wanted to ask some questions of the author via PM and now can't.

gunnut41

[Dave B]

I am not sure about that previous post but a guy I knew told me about his tempering of springs using a quart jars metal  lid filled with oil with the spring laying in the oil up to the halft way point of the spring. Maybe 3/16 deep. HE would light off the the oil and let it all burn away. The temp oil burns at is 600 degrees and is a good solid way of tempering a spring and keeping the mosquitoes at bay.

[Dphariss]

I am not sure about that previous post but a guy I knew told me about his tempering of springs using a quart jars metal  lid filled with oil with the spring laying in the oil up to the halft way point of the spring. Maybe 3/16 deep. HE would light off the the oil and let it all burn away. The temp oil burns at is 600 degrees and is a good solid way of tempering a spring and keeping the mosquitoes at bay.

This is the temp of the oil flame. Not the oil or the part.
Myself and others have been puzzled how this works. It apparently does but from what I have read it technically should not.
I like to use a potassium nitrate bath. Melts ate about 700. Immerse the part heavy sections first to evenly heat the part and watch the colors change. Might want to do a trial on a piece of scrap to get the hang of it.
Suppliers like this one are the cheapest way to purchase. Same stuff and Brownell's nitre bluing "salts" but a lot cheaper as granules.

http://www.dudadiesel.com/search.php?query=%22potassium+nitrate%22


Also good for "fire bluing" parts.
Everything washes off clean with a short soak in warm water, dry, oil and install the part. No smoke etc etc.
Heat the solidified nitrate from the sides, not the bottom allow NO WATER within FEET of the liquid nitrate. Water in this stuff is as bad or worse than in lead. Steam explosion. Wear protective clothing just like for casting bullets.

Dan

[Old Ford2]

If you have an electric lead melting furnace ( which most of us have ) you can bring the furnace to temperature then go through the cooling process. Resulting in a well tempered spring!
Have a great day!
Fred

[Captchee]

 what your looking for is covered under Kit Ravenshears ;Simplified  V springs ,A guncraftsmanship Manual .
 basicly after hardening the spring , you draw it back" Temper  it "  using the oil  burn off meathod
 yes  the oil  treatment works  and works well . i have done it that way for years .
 it is troublesome with small leaf springs like a sear spring  . i think maybe becouse these float around in the oil as its boiling and burning off . frankly im not sure .

[James Wilson Everett]

Guys,

The correct spring tempering temperature depends greatly on the carbon content of the alloy used to make the spring. The alloy I use is certified 1095 carbon steel and I temper it at 810F.  This is well beyond the temper color range, actually it is nearly dull red in the dark, but not quite.  Folks who use spring steel with a lower carbon content - like 1075 or whatever, will use a lower tempering temperature.

At one time I used old automobile springs, old files, etc. for spring making.  But, I have repented of this after having too many break or bend due to an improper guess at the correct temperature.  If you do not know the alloy you are using then is really is a guess, too!  Ever since I decided to use only good - for sure  AISI 1095 carbon steel and heat treat in a careful and controlled manner, I have had much better success.

Jim

[Curtis]

gunnut41,

Is this the post you are looking for??
http://americanlongrifles.org/forum/index.php?topic=7112.0

[Long John]

Here is why I think the burning oil method works for many steels some of the time.  I have used it successfully for PB springs.

When you light off a combustible liquid fire the flame must heat the liquid beneath it to its boiling point in order to provide vaporized fuel to perpetuate the flame.  The highest the liquid temperature can get is its boiling point.  So, while the oil is burning you get a bath of boiling oil at its boiling temperature.  If you select the oil with the right boiling temperature for the steel you are heat treating then the method works wonderfully.  If your oil boils at too low a temperature then the steel will never achieve the intended temper.  If your oil boils at too high a temperature then the spring will be too soft.  Fortunately, most motor oils have well defined boiling temperatures.  The boiling temperature will be found on the MSDS.

Best Regards,

John Cholin

[LRB]

  Common motor oils I checked boil at 400° to 500°. That is much too low of temp to temper a spring. The heat would have to come from the flame.

[Dphariss]

http://micapeak.com/info/oiled.html

Flashpoint is the number I think we are looking for rather than the "boiling" point.

Dan

[Jim Kibler]

The basic idea of tempering is to pick the highest temperature such that little plastic deformation occurs when the spring is cycled in service.  In other words so the spring doesn't change from its original shape or take a set.  Hardness does not influence the strength or restisance to shape change with in the elastic range.  By picking the highest highest tempering temperature, the spring is softened to the maximum degree and is therefore least susceptible to defects and stress risers contained in all materials.  This said, I have bee selecting tempering temperatures that should yield hardnesses in the low to mid 40's on the Rockwell C scale for mainsprings.

Jim

[Dave Faletti]

The highest tempering temp would  take it back to the annealed state. Hardness should influence what the elastic range is.  A spring thats glass hard stays in the elastic range until the failure point. I am not disagreeing with you Jim just a bit puzzled on your description.  Obviously there must be an alloy, and heat treatment that maximizes the elastic strain and toughness but I don't know what determines that.

I can see how the oil trick works but seems like the hard way there.  The oil thats liquid will pre-heat the part and regulate to a degree the part of the spring thats above the liquid.  The exposed part will be hotter than the liquid but lower than the flame temp. 

[Jim Kibler]

Dave,

The hightest tempering temperature such that a hardness results where no or little plastic deformation occurs when the spring is in service.  In other words as soft as you can get it, such that when you put the spring in service it returns to or nearly to it's original shape.  The softer you can get it, the less sensitive it is to defects that are inherint in any material.  Hardness will not affect the strength of the steel if working within the elastic region.

Jim