Tempering mainspring

[Justin Urbantas]

Hey guys. I have a cast Siler mainspring I need to adjust a bit. After hardening, what temperature do you temper them at? Thanks

[Clint]

I would probably heat it up to 800-F . If it felt spongy I would anneal it reharden it and reduce the temper to 750-F. Jim Chambers could probably what temperature they heat to.

[Dave B]

I just made a successful main spring #2 for my English lock a couple weeks ago and tempered it by soaking in a pot of just molten lead (600 F) for 20 minutes. The first attempt at the spring I did the wing it with a torch. Even though I had a nice blue all the way through, this what happened when I put it in the mainspring vice to get that last little bit to get it into the lock ...just one more turnnn.... Snappp!  The lock in the pic is the soaked in lead spring installed. No issues what so ever. Jerry Huddleston deserves the credit. I went back through my Oregon gun makers fair notes and he did a Make your own main spring presentation and forged up a flintlock main spring and talked through the whole heat treat and such. See Jerry, I can be taught or that, I do listen from time to time.

[Pukka Bundook]

Dave,
I liken testing a new mainspring to bomb disposal, for being nerve-wracking!
But you probably know this.  :-)

[James Wilson Everett]

Guys,

The answer will be greatly influenced by the alloy used to make the spring - I suspect 1075, but I do not know.

I have made a great number of springs using 1095.  Heat to 1450, quench in brine without stirring or swirling the part.  Temper at 810.  Please realize that the heat treating of steel will not effect the load/deflection property in any way - not at all.  Identical springs tempered at 650 or 750 or 850 will all have an identical load/deflection characteristic.  The only way to make a spring stronger or weaker is to change its physical shape, size, or thickness.

Here is a quote from people who know:

The Iron Age Volume 89 May 9, 1912, page 1151

The stiffness of a piece of steel cannot be increased by alloying nor by heat treatment.  By this I mean that provided the elastic limit is not exceeded, the amount of deflection for a given load cannot be decreased.  However, heat treatment will raise the elastic limit so that a much greater load can be carried without causing a permanent set.  Until the elastic limit is reached all steels, no matter how treated or of what nature, will deflect the same amount under the same load.  However, the poorer grade steel or the un-heattreated one will reach its elastic limit first and will then deflect much more and retain a permanent set.


Jim

[smart dog]

Hi Justin,
I reshape, harden and temper Siler springs all the time.  The formula I settled on is heating to bright red and quenching in Canola oil.  I actually quench in 2" of canola oil floating on top of room temperature water.  Then polish the spring and heat to 750 degrees for 1 hour.  For springs as small as Siler's probably 30 minutes is plenty but I do a full hour.  The tempering temp does not have to be all that precise, however, I found that at 800 degrees or above the springs take a set and below 700 degrees I risk occasional breakage.   I have a programmable oven and can control the temps very precisely so was able to experiment over the years.  Siler springs are cast steel and not 1075 or 1095 steel.  I believe they are an alloy with 60 points of carbon.

dave

[shifty]

Hi Justin,
I reshape, harden and temper Siler springs all the time.  The formula I settled on is heating to bright red and quenching in Canola oil.  I actually quench in 2" of canola oil floating on top of room temperature water.  Then polish the spring and heat to 750 degrees for 1 hour.  For springs as small as Siler's probably 30 minutes is plenty but I do a full hour.  The tempering temp does not have to be all that precise, however, I found that at 800 degrees or above the springs take a set and below 700 degrees I risk occasional breakage.   I have a programmable oven and can control the temps very precisely so was able to experiment over the years.  Siler springs are cast steel and not 1075 or 1095 steel.  I believe they are an alloy with 60 points of carbon.

dave   

    I am not much of a spring maker , could you explain the purpose of having the Canola oil floating on top of the water for quenching .  thanks

[tallbear]

I have used Jerry Huddleston's lead bath method successfully several times.......https://americanlongrifles.org/forum/index.php?topic=40158.0


Mitch

[Dave B]

I forged the springs from a section of heavy coil spring I found along side the road. It looks like one of those they use for the tipping door style for your garage. Its a bit over a 1/4" in dia. not quite 3/8".

[smart dog]

Hi,
I use the oil on water to cool the metal faster while reducing the shock of the hot metal hitting water directly.  I adopted this method primarily for quenching parts made from 1075 and 1095 steel but it works for cast springs as well.  It works very well completely eliminating any risk of surface cracking while still cooling the parts very quickly.  I am sure brine would work just as well.
dave

[P.W.Berkuta]

I have made MANY springs using 1075, 1084, and O-1 steel. I find 1075 to be the best for me. I have used Kit Ravenshear little book in which he describes the 'oil burn off method" to some success and I have used the "heat the spring on a flat piece of steel till dark blue/gray method" but the most successful method is the lead bath method I have found.

[jerrywh]

I temper my springs at 725° F for 15 or 20 minutes either in an oven or a lead pot wit ha lead thermometer.  I recently tested my lead thermometer with a Thermocouple digital.  The difference is negligible. You might get by with any temp over 625° but the 625° temp is for coil springs and is a little risky for a leaf spring. it is very important to hold the temp for at least 12 minutes. I always harden springs in oil. If you just leave the oil on the spring it will stop the lead from sticking on it.

[Bob Roller]

Melting lead has never been part of my spring making and burning off the oil has been for me,a failure.
After the spring has been forged,filed and ground to shape it is opened up to set the shape and preload.
It is then heated to a bright orange and dropped into a can of  5W-30 oil and allowed to cool and then it
is removed with a magnet and using a kerosene bath the oil is removed and the spring dried with a shop
cloth and then completely polished.Using a Bernz-O-Matic torch with an adaptor to focus the flame and
holding the spring by the stud that goes thru the lock plate it is drawn to a dark blue with special attention
paid to the bend where it is the thickest. This works for me and I have a LOT of locks in use world wide and
for a lot of years with no reported failures of springs of any kind.I have used 1075 since 1957 when I was
given a sheet of it by P.I.Spence in Marietta,Ohio.I do not worry about broken springs and having never been
involved with bomb disarmament I have no comparison to draw on.
Bob Roller

[Daryl]

Pure lead or alloy, and if alloy, what alloy? Or does it matter?
I would expect no soldering/sticking happening with pure lead.

[davec2]

Bob,

Thanks for the explanation of how you work a spring.  I would pay money to watch a video of you making a main spring from scratch...

P.S.  If you have never disarmed an explosive device you may not have lived life to the fullest.....

[kudu]

I dont have the stock in front of me , But I bought my material from Brownells and
if I remember it says to anneal at 725 degrees F.

I only made about 4 springs and they all were done in a lead pot with a Thermometer
and the still work.

[Scota4570]

Of the dozen or so springs I have made lately I tempered them all at 750* for about 20 min.  I use one of my Lee bottom pour casting pots with a Lyman thermometer.  All of the springs work fine, none have broken.

[Bob Roller]

Bob,

Thanks for the explanation of how you work a spring.  I would pay money to watch a video of you making a main spring from scratch...

P.S.  If you have never disarmed an explosive device you may not have lived life to the fullest.....

You're welcome.My methods might rank with the stone axe but success tells its own story.
I lay NO claims to perfect work because it is not perfect but useable.
As far as bombs are concerned,I think a real hoot and giggles occur when some knucklehead
has one to go off in his face while setting it to hurt others.A police officer told me of a man that
was planting one in a garbage can during a festival and it went off and left few identifiable parts
and nobody else was hurt. .
Bob Roller

[jerrywh]

Pure lead or alloy, and if alloy, what alloy? Or does it matter?
I would expect no soldering/sticking happening with pure lead.

Daryl. the main reason for a lead thermometer is in case it is not pure lead. Some lead alloys melt as low as 200°F. That could spell disaster. I guess I have used every spring steel alloy there is and They all tempered at the same temp. and with no problems. 1075 is my all-time favorite. I just forged two springs that had to be the exact length and same configuration. One was a tiny sear spring and the other was a mainspring that that t fit between a lock and the tumbler with no room to spare. The trick is making the bend in the exact spot.

[Jim Chambers]

We make our springs out of 6150 carbon steel.  We heat them to 1550 in an atmosphere controlled furnace, quench in oil, and draw them at 750 for an hour.  Hope this helps

[Justin Urbantas]

Thanks  for all the responses. I'll go with my lead pot for an hour at 750, then into canola oil

[rich pierce]

Pure lead or alloy, and if alloy, what alloy? Or does it matter?
I would expect no soldering/sticking happening with pure lead.

I smoke them in a candle flame before submerging in the lead pot. This prevents tinning.

[jerrywh]

Jim. Why do you use 6150. I call that fool proof spring steel, because it is so forgiving.

[D. Taylor Sapergia]

Thanks  for all the responses. I'll go with my lead pot for an hour at 750, then into canola oil

Justin:  first harden the finished spring by heating to bright red and quenching in Canola.  Then re-polish being careful not to flex or drop the spring as it will be hard as glass and may shatter if dropped on concrete.  Then melt your pure lead in your pot, resting the spring on top of the lead.  When it melts, keep the lead at that temperature for the next twenty minutes.  Remove the spring and place it on a piece of wood to cool.  Don't quench it in oil.  The idea is to keep the spring at the tempering temperature over a period of time, so that it gets a uniform soak at the correct temperature.
Jerry Huddleston once likened it to baking a cookie....it may be perfect on the outside and still raw dough on the inside, if done at too high a temperature and taken out too soon.

[heinz]

I use the same process as Bob Roller.  When dealing with cast springs you have to realize you are working with a casting that has been designed to look like a forged spring.  If an engineer designed that casting from scratch I think the knuckle would be shaped differently.  Bearing that in mind I do my anneal heating on cast springs primarily on the knuckle: it will make little difference if the knuckle is a little soft, it is not likely to deform much but, if too hard, it is likely to break.