Mainspring Tempering Trouble

[JBulitz]

I'm hoping that for you folks who have made/modified any number of lock springs, your introduction to doing so was as rocky and full of bungled attempts as mine...  Which lead me here.  I have an antique Ohio rifle that's been restorable to solid functioning condition to this point.  The final piece that needs replacing is the mainspring, which was broken at the bend: This beautiful little rifle doesn't deserve the floppy hammer and is otherwise fit to punch paper.  It's a Golcher-style percussion lock (sans the usual "Golcher" banner engraving), however the springs in Golcher reproduction from R.E. Davis are far too long for this particular lock.

I meticulously made three springs in total, based on the pieces of the original, using spring steel flat-stock: finally on the third attempt, I'd learned from my mistakes enough to really nail the shape and fit, and thus moved on to harden and temper it.  Per a small spring-making booklet by Kit Ravenshear, I heated and hardened the spring in motor oil, and then tempered it by immersing it in the same oil and setting it ablaze to burn off.

When I cleaned the spring and put it into the lock, it bent perfectly... then stayed that way.  I tried the tempering process a couple times over with the same result, making sure it was cherry-red before hardening, etc.  What am I missing?  Is it possible to "burn out" the spring steel's ability to harden and temper properly by overheating or heating too many times?  Would really appreciate hearing what others' process is. 

[Daryl]

You used too much heat when tempering and annealed it. I'm sure others will chime in to help. I've done exactly as you have.

[Ross Dillion]

What type of steel is your “spring steel stock”. Depending on what it is that type of heat treatment may not be appropriate.

[smart dog]

Hi,
It would be good to know the spring steel alloy.  It sounds like you never really hardened the spring.  Try heating it bright orangy red and quenching in canola oil, not motor oil.  Kit's tempering method is a bit hit or miss.  I use a heat treating oven and hold the springs at about 750 degrees for 1 hour to temper them.  Heating them in a lead bath held at above 700 degrees will work as well.

dave 

[rich pierce]

I harden a sacrificial sliver of steel. Say 2” long and 1/8” wide. Harden it and test with a file. Then I clamp it in a vise with an inch sticking up and smack it sideways with a hammer. If truly hard it will snap off cleanly. In my shop I find the piece much later. This tests the steel and your technique. If not hard change the technique. Of changing the technique doesn’t work then give up on that piece of steel. I have never failed to test something I hardened with a file. Never assume it hardened properly.

[bama]

I use transmission fluid as a quench oil for the springs I have made and it works well. I also do the file check to make sure the spring did harden. Most of the springs I make are small so I polish them to a bright finish then heat the spring to a blue purple color and quench again to stop the heat. This works about 95% of the time. I do main springs the same way except after polishing the spring bright I cover the spring in motor oil and burn the oil off. I don’t really like that method but I don’t have a heat treat oven. I am going to try the lead bath one my next main spring.

[Bob Roller]

I have used annealed 1075 for over 50 years and have copied as closely as possible the shapes and contours of the English lock makers.I have locks all over the world and NO
reported failures.I taper the lower and upper limbs by using a milling machine and filing the cutter marks away and no more.I have a vertical fixture made from a 1/4x1/2 scrap and tapered and curved and then I set the polished and still flattened spring on this and tap it to start the spreading process and then heat the spring to a dull orange and gain by tapping it with a light hammer it is spread and the contour is established.It is then heated to a bright
orange and quenched in oil that was probably drained from a diesel bus engine years ago.
After it cools off I get it out of the oil with a magnet and wash it with kerosene and then dry it,repolish and then,holding the spring by the "pin"that goes thru the plate with duck bill pliers I start the "draw"at the upper end of the top arm of the spring and watch the color change to the bend and the give the flame a short residence time at the bend and continue
to the thin end where the claw resides that connects the lock to the link that makes the lock a lock.I call this method "Hillbilly metallurgy"but success is the reward and I won;t even think of altering it.The sear spring gets the same treatment.Before the rest of the lock is hardened and tempered I assemble the lock and test the springs and if the look and feel good the the lock is finished and the final assembly and test is done.I know this eats time but to me,taking the time to do this in what is proven right is the whole idea.
I almost forgot.The color I see is dark blue for the tempering which IS partial annealing.
Bob Roller

[JBulitz]

Thanks much folks, I'm overwhelmed by all the extremely helpful responses!  Learning to scratch-make one is worth all the trial-and-error to me as a "young'un" of 26 just delving in.

I was hoping I wouldn't have to answer that question about the alloy, since the stock is secondhand... It was given to me by a fellow gunmaker who claimed to have made a few v-springs with it, and it's worked just fine as far as leaf-springs go for patchbox releases, etc.
...But I realize that a patchbox release bends a whole lot less than a mainspring and agree that I really need to find a less mysterious steel first and foremost.

I don't have a tempering oven either, so I'm glad to hear the oil immersion method works for others at least some of the time.  I'll probably try polishing and "drawing" the color as you suggested, Bob.  The tapered fixture is also an extremely helpful trick which I'll probably try!

Any other tips and tricks even beyond these are appreciated as I try again... And probably again, and again.

[Bob Roller]

Making a "spring" with mystery metals is a guarantee of failure and frustration.I became aware of 1075 in 1957 and was given a sheet of it by a man who owned a machine shop in Marietta,Ohio.So far,nobody has given any reason to abandon it.Practice and try to develop
methods you are comfortable with.Over 60 years for me and IF I decide to finish the fancy 4pin lock that's been on my bench for about 14 years the springs will be just one more item,nothing more,
Bob Roller

[Scota4570]

I would not risk my time to make a spring with an eyeball method.  It is my observation that those with decades of experience making thousands of springs can use eyeball methods to draw the spring.   I only occasionally make a spring.  I use the lead bath and thermometer method.  I have not had any problems doing it that way.  Since I have my casting pot on the bench already it is no bother to do it in a controlled way. 

[D. Taylor Sapergia]

I've had a lot of success too, making mainsprings, and received a nice parcel from Bob Roller several years ago with some of the steel he uses so successfully.  I have a two litre can of used motor oil that is my quench tank.  To draw the temper, I have used three methods, all of which have worked.  The first is the lead bath, where I float the spring on the just melted lead for about 15 minutes then remove with a wire hook and place it on a piece of wood to come to room temperature.  the second, is the oil burn off method.  I was amazed at how long it took to get the oil to ignite, using just a propane torch outside.  But that worked nicely.  The third method is to place the spring on a 1/4" piece of copper plate so that it lays on its edge.  I drilled a hole in the plate just deep enough to receive the spring's tit.  I heat the plate, held in my vise, from the bottom with a propane torch, playing the heat over the entire bottom of the plate.  A drop of oil on the plate starts to smoke at about the time the spring is getting ready to change its temper colours.  I watch the spring go through its temper colours, ie:  straw, yellow, brown, purple, dark blue, bright blue.  At this time, I take the heat away and let the plate and spring come to room temperature without interference.  Jerry Huddleston (RIP) once said that just because the cookie is brown on the outside, it doesn't mean that the dough on the inside is cooked.  So the cookie and the spring need to soak at temper heat for a period of time so that the metal is cooked right through.  When the spring is cold, I can remove it and compress it with a mainspring clamp and set it into the lock.
A note about oil:  used motor oil is likely not the best.  The suggestion of using canola oil is a good one, and you might even bring the oil up to about 175 degrees on a hot plate first, before you dunk your spring.  Oil at room temperature, especially sitting on a shelf against an outside wall in a basement shop might be an awful shock to a orange hot piece of steel.

[Dan Fruth]

Ive made several springs with 1070-1095 steel and here is my method.

  Heat finished spring to bright orange, or until a magnet will not stick to the steel.
  Quench in transmission fluid.
  Test hardness with a file. If the file skates across the steel, it is hardened.
  Polish spring and soot with a candle.
  Heat lead in a lead pot to 750 degrees. I use a thermometer to check temperature  https://www.homedepot.com/p/Winters-Instruments-TBM-Series-3-in-Dial-Thermometer-with-Fixed-Center-Back-Connection-and-4-in-Stem-with-Range-of-20-1000-Degrees-F-C-TBM30040B13/205962790

  Immerse the spring in the lead and soak at temp for 10 minutes.

  Take out of lead and air cool.

  This has been my method and it works every time.

Good luck

 

[Jim Kibler]

Everybody has methods that work for them, but in general, pick a steel with say .05%-.08% carbon (ex. 1050-1080), harden properly (oil quench suggested, best choice is a proper medium to fast commercial quenching oil), and temper to about 40-45 HRC.  To determine the temperature to achieve this hardness, reference a tempering chart (hardness versus tempering temperature) for the particular alloy being used.

Proper quenching oil can be purchased from knife makers supply or places such as McMaster Carr.

You can use higher carbon content alloys, but I think they are a little less forgiving of process variations.

Jim

[JBulitz]

Folks,
I'm overwhelmed by all of the excellent information passed along; my optimism is totally restored, and I'll get some photos on here once I'm finally successful!  Very appreciative that even the experts will readily help a greenhorn like me out.

[RAT]

I once tried to make a main spring out of steel I cut from a large truck suspension coil spring. It did the same thing you describe. I suggest ordering a piece of 1095 from Jantz supply. They have thicknesses up to 1/4". I believe the lengths are around 12"-18", so you don't have to buy a huge length. The prices are very reasonable. It comes annealed and ready to work.

I harden by heating to bright orange with a MAPP torch and quenching in vegetable oil. I temper in a melted lead bath as described above. I use my electric lead melter for bullet casting to melt the lead.

[Bob Roller]

I am convinced that 1075 will forgive all varieties of abuse and home brewed ideas.
When I was in "Middle School" 7th to 9th grades I would stop at George Killen's gun
smith shop which was also his home and he would go the the nearby junkyard and get
flat section coiled springs as used on car hoods and deck lids and then put them in an old coal burning stove and anneal them and straighten them so he could measure a length he could use for whatever he was working on.His heat source was a home made blow torch that used white gas and he made this device using a big copper cylinder from a fire extinguisher and he pumped it up with a tire pump and when he fired it up after preheating
the nozzle it roared like a jet engine.Those hood.trunk lid springs were inconsistent in alloy and tempering was guess work at best.After I got that sheet of 1075 from P.I.Spence in 1957 I was able to learn what it took to make a reliable spring.Later I gave George Killen some and he thought it was a magic material and I have said if I have strip miles long I can
cut off 6 inches from each end and make two springs that can be trusted to work.In stand by that statement today.George passed away in 1977 and was a WW1 veteran,a loner and dangerous and morally abandoned.He took vacations in the Spring in the row of "Cat Houses"that were a fixture along the industrial area of 2nd Avenue.  .
Bob Roller

[Dphariss]

I'm hoping that for you folks who have made/modified any number of lock springs, your introduction to doing so was as rocky and full of bungled attempts as mine...  Which lead me here.  I have an antique Ohio rifle that's been restorable to solid functioning condition to this point.  The final piece that needs replacing is the mainspring, which was broken at the bend: This beautiful little rifle doesn't deserve the floppy hammer and is otherwise fit to punch paper.  It's a Golcher-style percussion lock (sans the usual "Golcher" banner engraving), however the springs in Golcher reproduction from R.E. Davis are far too long for this particular lock.

I meticulously made three springs in total, based on the pieces of the original, using spring steel flat-stock: finally on the third attempt, I'd learned from my mistakes enough to really nail the shape and fit, and thus moved on to harden and temper it.  Per a small spring-making booklet by Kit Ravenshear, I heated and hardened the spring in motor oil, and then tempered it by immersing it in the same oil and setting it ablaze to burn off.

When I cleaned the spring and put it into the lock, it bent perfectly... then stayed that way.  I tried the tempering process a couple times over with the same result, making sure it was cherry-red before hardening, etc.  What am I missing?  Is it possible to "burn out" the spring steel's ability to harden and temper properly by overheating or heating too many times?  Would really appreciate hearing what others' process is.

First off stop using motor oil. Use a mix of ATF and Diesel or Marvels Mystery oil with a little diesel. Then HEAT THE OIL till its at least warm to the touch I like well over body temp. Cold oil quenches more slowly, it does not conform to and cool the part as warm oil does.
I use melted Potassium Nitrate  (saltpeter) in small steel container to draw them back. Put the spring in using a wire. It will immediately skin over with hardened Potassium Nitrate. Then watch CAREFULLY as the “skin” melts off leaving the heavy section in and easing the thin sections out to prevent over heating the thin areas. Let cool and wash off the PN with warm/hot water soak as needed.
Some use molten lead the same way.
I bring small parts to blue with a propane torch.
NOW. You should be able to find the Potassium Nitrate at suppliers for the equipment to make biodiesel from cooking oil. It comes as pellets. But once melted it turns hard. If you reheat it you must heat at the sides then slowy down to the bottom to prevent possible explosions since as soon as it melts it creates oxygen and you don’t want a trapped oxygen bubble at the bottom. AND its REALLy hot. Like molten lead so wear face shield and protective clothing. Or buy an electric furnace.
Unless its a really stubborn piece I would not use water as a quench
AND
You have to experiment and find what works for you if doing it it with forge/torch.
Also use O-1 for springs and like it. But have made them from 1095 and really like 1070 +-. Note the heat soak requirement I have seen mentioned for O-1 only pertains to heavy cross sections 1” or thicker.
AND many of us has a way they have learned and works for them.
The saltpeter bath can be used to blue parts. If coated with oil then carefully heated to smoke off the oil the blue will darken nicely. ‘The Winchester Book” by Madis has a photo of a hand written description of this process used by Winchester for barrels and other parts  in earlier years. They added some “peroxide of Manganese” (which is possibly Manganese Dioxide) to the melt. 

[P.W.Berkuta]

Every one of the above answers are what works for that person. I bet "dollars to doughnuts" that those individuals had to try many different processes before settling on one that worked for them. Once they found that "magic potion" they stopped looking for other ways of hardening and tempering the spring. I first used Kit's method back when I made my first spring in 1968 using a piece of 1075 that I purchased from DGW. It was a hit or miss process and messy. The spring steel was the right one to use but the process was not. I now build a little fire box out of fire brick - open front and a little air gap at the rear so that the flame from a torch can pass through. I heat the steel up in two stages - first I bring it up to red heat and let it cool slowly (this arranges grain structure) then I reheat to a salmon/orange color and quench in warm vegetable oil or a mixture of warm transmission fluid and water 50/50 (float the trans fluid on the water) use enough of this to cool the heated spring (about a pint or more) quickly. Check with a file then go directly into a 750 - 800 degree lead bath for around 10 minutes. You can also use your oven set to 500 - 525 degrees but ovens vary in temps so they must be checked with a good thermometer - let spring soak for one hour then shut off oven and let cool until spring can be handled. Check spring for function. Do not let a freshly hardened spring sit for long (like hours or overnight) before tempering or it WILL develop stress fractures. A soft spring cause most likely is either too low of a hardening temp or too high of a tempering temp. If the spring did not break in testing, you can do the process over changing your hardening temp or tempering temp - good luck with your adventure.

[kudu]

I use 1075 from Brownells.
I also have heat to bright orange and quenched in water which is NOT recommended but man is that steel hard afterwards.
I also temper the spring in lead pot as close to 729 degrees as possible for only about 15 -20 minutes.
Works good for me?

[LRB]

Ive made several springs with 1070-1095 steel and here is my method.

  Heat finished spring to bright orange, or until a magnet will not stick to the steel.
  Quench in transmission fluid.
  Test hardness with a file. If the file skates across the steel, it is hardened.
  Polish spring and soot with a candle.
  Heat lead in a lead pot to 750 degrees. I use a thermometer to check temperature  https://www.homedepot.com/p/Winters-Instruments-TBM-Series-3-in-Dial-Thermometer-with-Fixed-Center-Back-Connection-and-4-in-Stem-with-Range-of-20-1000-Degrees-F-C-TBM30040B13/205962790

  Immerse the spring in the lead and soak at temp for 10 minutes.

  Take out of lead and air cool.

  This has been my method and it works every time.

Good luck

 

Do not count on non-magnetic as a quenching guide. Non-magnetic is only 1414°F. You will need about 60°/65° more to get a good hardness. As you said , a bright orange or even a red-orange will do. Do not allow the steel to go as far as yellow.

[flatsguide]

I'm hoping that for you folks who have made/modified any number of lock springs, your introduction to doing so was as rocky and full of bungled attempts as mine...  Which lead me here.  I have an antique Ohio rifle that's been restorable to solid functioning condition to this point.  The final piece that needs replacing is the mainspring, which was broken at the bend: This beautiful little rifle doesn't deserve the floppy hammer and is otherwise fit to punch paper.  It's a Golcher-style percussion lock (sans the usual "Golcher" banner engraving), however the springs in Golcher reproduction from R.E. Davis are far too long for this particular lock.

I meticulously made three springs in total, based on the pieces of the original, using spring steel flat-stock: finally on the third attempt, I'd learned from my mistakes enough to really nail the shape and fit, and thus moved on to harden and temper it.  Per a small spring-making booklet by Kit Ravenshear, I heated and hardened the spring in motor oil, and then tempered it by immersing it in the same oil and setting it ablaze to burn off.

When I cleaned the spring and put it into the lock, it bent perfectly... then stayed that way.  I tried the tempering process a couple times over with the same result, making sure it was cherry-red before hardening, etc.  What am I missing?  Is it possible to "burn out" the spring steel's ability to harden and temper properly by overheating or heating too many times?  Would really appreciate hearing what others' process is.

First off stop using motor oil. Use a mix of ATF and Diesel or Marvels Mystery oil with a little diesel. Then HEAT THE OIL till its at least warm to the touch I like well over body temp. Cold oil quenches more slowly, it does not conform to and cool the part as warm oil does.
I use melted Potassium Nitrate  (saltpeter) in small steel container to draw them back. Put the spring in using a wire. It will immediately skin over with hardened Potassium Nitrate. Then watch CAREFULLY as the “skin” melts off leaving the heavy section in and easing the thin sections out to prevent over heating the thin areas. Let cool and wash off the PN with warm/hot water soak as needed.
Some use molten lead the same way.
I bring small parts to blue with a propane torch.
NOW. You should be able to find the Potassium Nitrate at suppliers for the equipment to make biodiesel from cooking oil. It comes as pellets. But once melted it turns hard. If you reheat it you must heat at the sides then slowy down to the bottom to prevent possible explosions since as soon as it melts it creates oxygen and you don’t want a trapped oxygen bubble at the bottom. AND its REALLy hot. Like molten lead so wear face shield and protective clothing. Or buy an electric furnace.
Unless its a really stubborn piece I would not use water as a quench
AND
You have to experiment and find what works for you if doing it it with forge/torch.
Also use O-1 for springs and like it. But have made them from 1095 and really like 1070 +-. Note the heat soak requirement I have seen mentioned for O-1 only pertains to heavy cross sections 1” or thicker.
AND many of us has a way they have learned and works for them.
The saltpeter bath can be used to blue parts. If coated with oil then carefully heated to smoke off the oil the blue will darken nicely. ‘The Winchester Book” by Madis has a photo of a hand written description of this process used by Winchester for barrels and other parts  in earlier years. They added some “peroxide of Manganese” (which is possibly Manganese Dioxide) to the melt.

Dephariss, Do recall what chapter the “...hand written description...” was in the Madis book. I tried to find it in my Madis book but must have overlooked it.
Thanks Richard

[Bob Roller]

First starts are frequently "bungled"and whatever works is just THAT.My own primitive methods work for me and decades of no broken springs speak for me.I have had some liars try to get free springs by claiming they have my locks with broken springs and I hut that down by demanding the locks AND the broken springs.A well know Hawken maker has a customer that tried that swindle by saying he had 4 Hawken locks I made and ALL the springs were broken.He hung up when I told him I did not believe him and wanted ALL the locks back WITH the springs that "broke".
Bob Roller

[JBulitz]

Well folks, I finally managed thanks to everyone's input.  Many thanks once again.  Perseverance paid off on the 1st try with this steel and now I'm proud to be confident in a new (and important) skill!

I got my hands on some 1075 steel, which I hewed into the spring you see here before a succesful quench in canola oil.  With some further advise from an experienced friend, I then ignited some 10W-30 BEFORE placing the spring into it and allowing it to burn off.  It worked wonderfully- after gently breaking in, the spring did not slacken or bend whatsoever.

Now on to the tumbler.  The last person to work on it appears to have annealed it in order to peen the shank (rather than replace a missing hammer bolt) and to cut some odd notches which need to be dealt with.  One step closer...

[Curtis]

Looks like it turned out great!  Nice.

Curtis

[Dphariss]

Dephariss, Do recall what chapter the “...hand written description...” was in the Madis book. I tried to find it in my Madis book but must have overlooked it.
Thanks Richard

It sometimes takes me awhile to find it. Its in “Extras and Special Order Features” Chapter 32.

Pg 608