Heat treating spring stock

[smallpatch]

Ok, I know I've asked this before. 
How do we heat treat the thin spring stock from MBS?
I know to heat to red, quench in oil, but what about drawing it back?
Sorry for asking again.

[M. E. Pering]

Hey, Smallpatch.  It shouldn't really matter who the supplier is.  Spring steel is spring steel.  I use 1095 myself.  But after your quenching, you should polish the spring.  Once you get it nice and shiny, you want to very slowly heat it up.  600 degrees Fahrenheit is around where you want it for tempering, and if you can hold it there for a bit, it is better.  But with thin, small springs, this is very hard to do.  The lead treatment is best, assuming you have pure lead that is truly liquid at a little over 600.  Submersing it in that liquid for about 60 seconds would probably do the job.

However, if you can't do that, you will need to look for color change in the spring.  At bright blue, you are almost there, at Grey Blue you are there, and after that you will start to see redness, and that is not what you want.  I have actually tempered to the bright blue color, and never seen any consequence from not going further.  Also, do not quench after you get to the desired temperature... Just let it cool naturally.

M. E. Pering

[smart dog]

Hi Dane,
How thin and what is the spring for?  I normally heat soak springs of 1075 steel at 750 degrees for 1 hour in my oven.  However, for really thin stuff I simply harden it, polish the surface and then slowly heat it to deep blue and then a little more until it turns a light sky blue.  I then let it cool.  I use a butane mini-torch for this.  I just fixed the sear spring  action on a type 2 English dog lock that way.  The little "V" spring that holds the tail of the lateral sear out away from the plate is about as thick as steel banding or strapping. 

dave

[Bob Roller]

1075 has been my choice for over 50 years and I use the heat it orange/red,
quench in a light oil,get it out of the oil with a magnet,wipe it of,polish on both
sides and use a Bernz-O-Matic torch with an adapter to focus the fire in a very
small area and draw to a dark blue.The lack of broken springs on my locks and triggers
tells me this works.

Bob Roller

[David Rase]

To control the heat for tempering a thin spring I like to place the spring on top of piece of steel and heat the spring from the underside of the steel.  I use a length of 1 1/2" wide by 3/8" thick piece of steel and clamp it in my bench vise for this procedure.
David

The above method is what I used to temper the small spring for the lever in this powder horn spout.

[smallpatch]

Guys,
It IS 1095, and pretty thin.  It is for a patchbox opening spring. 
The problem I usually have, is seeing that change from dark blue to light blue.
I've heard about burning oil, lead bath, etc.
Just looking for a good consistent way.

[flehto]

I too temper a thin opener spring over a 1/4" heated steel bar clamped in my vise. I use a Mapp  Gas torch to heat the bar from  underneath and have a can of quenching oil handy to control the color. After bright blue comes the blue gray which is  the correct color for the spring. I always form the spring w/ a radius in all corners and "roll" the corners over the bar to  ensure that they're also blue gray. Never had one break......Fred

[D. Taylor Sapergia]

I make most of my patchbox kick springs out of worn out hack saw blades.  After shaping with the bench grinder, and polishing, I heat red and bend them to the shape I want, including the little curl on the tip, then re-polish, head red and quench in motor oil.  Re-polish to bright, and hold about three inches from the flame of a propane torch, rotating the spring and moving it through the washed out flame.  I watch the colours start, and move it a little further away.  This allows the heat to soak in the spring while it continues to come up in heat through yellow, straw, brown, purple - move it further yet - into very dark blue, into the beautiful shiny blue, to the light sky blue, and I remove it from the heat.  This produces a kick spring, or a latch spring for that matter, that is excellent. 
To temper springs that have a more parallel shape and that will sit level, I use a 1/4" thick piece of copper plate in my bench vise, heating slowly from the bottom.  This works best for springs that have contact to the plate over their whole length.  My kick springs do not.




the tyger by william blake meaning

[Canute Rex]

Hey Smallpatch,

Here are a couple of ideas to make it easier.

Polish it before you harden it. Then get a bottle of chalk line powdered chalk. I like blue, but any color will work the same. Wet the steel and dribble a little chalk on it, then rub the chalk around to cover the surface. You want a paste coating all over. Let it dry. This will create a fragile coating that will keep most of the oxygen away from the surface while you are heating the steel. When you quench it the chalk blows off. Much less polishing to do once it is hardened and brittle. Daryl Meier taught me that one.

Buy a few Tempilstik sticks. They look like chalk in a metal holder and they are made to melt at particular temperatures. You can get them from 125F to 2000F. Draw a line of 750F Tempilstik along the spring and heat it until the chalk line melts. http://www.tempil.com/tempilstik/

One man's opinion, but 1095 seems like overkill for a patchbox spring. That is, unless you want it to double as a mortising chisel. 1075/1085 is quite springy enough and a lot more forgiving during heat treating.

Hoping you keep a spring in your step,

Canute

[smallpatch]

Taylor,
That looks almost exactly like my spring.  I've tried it once, and I guess I went too far.  First use, it bent, not spring.
I guess I'll try again.

[P.W.Berkuta]

Have a look at this explanation on 1095 spring steel it may just help you: <http://metalsmith.org/pub/mtlsmith/V21.2/Springs.htm>

[D. Taylor Sapergia]

Two things can cause that:  not hard enough to start with, or drew temper too far.  Likely the first.

Holding the polished shaped spring by the big end with a loop of 1/16" welding rod, bring the steel to bright red/orange and quench in oil by swirling it in a figure eight.  Don't be tempted to bring it out too soon.  Cut the wire off and Clean off the spring with a cloth.  Re-polish, and temper.
Being too soft is easier to fix that too hard!  Just start heat treating all over, beginning with re-shaping and polishing.

[rich pierce]

I always check hardness before tempering. Can’t imagine not doing that, especially with lock castings or a piece of steel I have not hardened before. 

[smallpatch]

Taylor,
Voila! I made a spring!
Took me twice, but I got er done.

[rich pierce]

Nice!  Pretty cool when things work!

[M. E. Pering]

One thing I may have forgotten to mention... You need to break in a new spring.  Don't try and flex it totally at first.  Just gently flex it at first, and become more aggressive at it as you feel it can take.  This is what I always do, but before I started this practice, I broke a couple.  Also, any steel from 1075 to 1095 should yield a satisfactory spring.

 M. E, Pering

[Chowmi]

Being too soft is easier to fix that too hard!  Just start heat treating all over, beginning with re-shaping and polishing.

Taylor,
Your point brought to mind a theoretical question that I have had in my mind.  I have almost zero experience with this, so bear with me.

If I am hardening and tempering something, be it a spring, or not, what error in tempering requires starting again with re-hardening? 

As an example: 

I harden and quench a widget, lock bolt, spring etc etc.  I then wish to temper it.  Let's just assume that the proper tempering temperature for this particular item and it's intended use is XXX degrees C. 

If I overshoot to XXX C plus 50 (or 100) C, can I just let it cool and then try again and hit XXX degrees C? 
If I undershoot to XXX minus 50 (100) C, can I just try again after it has cooled? 

which is the error that requires re-hardening? 

I realize that I have used temperatures in the question, when it is likely that I will use colour in real practice.  I don't have accurate temperature measuring devices. 
In any event, the principle should be the same. 

I suspect your quote above is the answer, but I have suspicion that it may be more complicated than that.

Thanks in advance,

Norm

[smallpatch]

Norm,

If it's too soft,it will bend....... start over
If it's too hard, it will break......start completely over.

[GeezerD]

Many years ago, an old German gunsmith gave me a method for tempering gun springs. After hardening the spring to the point that a file won't cut it, place it in a small metal container and put in enough motor oil to cover it ( mineral oil ,not synthetic ). Use a propane torch to get the motor oil to start burning and let it completely burn out. Motor oil burns at a temperature that is just about perfect for tempering spring stock plus it keeps it at that temperature for quite some time until it burns out. I have never had a spring break after using this method. -------------------- GeezerD

[Angus]

Two thumbs up for the motor oil. Just enough to cover the spring, you will have to stay after the oil to keep it lit and burning til it's gone. Use a small can, sardines, tuna, cat food. And take it outside!

[LRB]

Have a look at this explanation on 1095 spring steel it may just help you: <http://metalsmith.org/pub/mtlsmith/V21.2/Springs.htm>

This is a pretty good bit of advice on this link. One exception to it is that he gives the melt temperature of lead as 700°, when it is really around 625°. Best spring temper is at 725° to 750°.

[Bob Roller]

Two things can cause that:  not hard enough to start with, or drew temper too far.  Likely the first.

Holding the polished shaped spring by the big end with a loop of 1/16" welding rod, bring the steel to bright red/orange and quench in oil by swirling it in a figure eight.  Don't be tempted to bring it out too soon.  Cut the wire off and Clean off the spring with a cloth.  Re-polish, and temper.
Being too soft is easier to fix that too hard!  Just start heat treating all over, beginning with re-shaping and polishing.

If it's a mainspring that's too hard and it breaks,forge it out flat and file it
into a "turnscrew"or a "schraubenzier".

Bob Roller

[D. Taylor Sapergia]

Norm:  Dane answered the question but to enlarge a bit, if you have hardened the steel to the point that a file just slides over it  and will not cut, and then temper the steel and go too far, you will have to re-polish and re-harden.  Just re-tempering will not restore the hardness you lost by overshooting the tempering heat.  I have read scientific treatises on this and it has to do with the way the molecules of the steel align themselves at various temperatures.  Picture sand, if too hard, and layers of newspaper for a spring.  Not a very good analogy.

[LRB]

  tempering is a slight repositioning of the iron and carbon atoms in their cubic atomic units which form crystal like structures that make grains, and tempering relieves some of the stresses in these atomic units. No molecules in metals. All crystal. To be short, some of the carbon atoms trapped in these units when you quench, move out of the cubics because of your temper heat, which make the steel softer.
 

[D. Taylor Sapergia]

I naturally defer to you LRB.  But is must be magic for sure.