Spring Temper Question

[Erzulis boat]

I have a very large Mainspring here, that is .225" at the bend and tapers to .140" at the tumbler engagement end.

I have successfully made mainsprings perhaps a third smaller, but this guy has me worried a tad.

I have Oxy/Acetylene so getting it to 1500/1550 for the linseed/motor oil dip is no sweat, but I am concerned that by bringing it back to a workable spring will not be thorough enough.

Any techniques to ensure that the temper is going to be throughout?

TRS has stated that a 5 minute soak (after it goes to temp. of course) in a heat-treating oven is ideal, but I know some of you guys are doing this just perfectly without.

Thanks- Andrew B.

 

[LRB]

What is the steel?

 

[Erzulis boat]

All the smaller springs from this lock (castings from TRS) went 1500/1550 in motor oil, then were drawn back to an even blue, and work just perfectly.

I will dig out my notes though, I might have this info at home- or I may have to try to get a hold of TRS :shake:

 

[Zonie]

IMO, the tempering temperature should be about the same for this spring as it is for other springs made of similar material but with a thick or heavy spring it is important to allow the entire spring to stabilize at that temperature.

Because the surface of the spring will come to color rapidly, let it soak at temperature for at least 15 minutes so that the entire spring reaches the tempering temperature and soaks there.

This won't overly soften the surface as long as the temperature is maintained correctly.

 

[J.D.]

A vast majority of cast mainsprings are made of 6150 steel, though it is possible that this one may be cast of some other material. A call to TRS should identify the alloy...and the correct tempering temp.

IMHO, tempering to a blue may not be enough. Blue colors form at about 560-580 degrees, and that may not be hot enough to insure a durable spring.

A good method for tempering most springs, including cast springs made of 6150 is to temper them in a lead bath at 620 degrees. Place the spring on top of at least 10# of pure lead and allow that lead to melt. Push the spring under, and either regulate the heat so's the lead remains just at the melting point, or remove the lead from the heat and allow it to to harden. place the lead back on the heat source and let it melt.

With a spring that thick, I would go through the process four or five times, for a total of about 30 minutes, or more, to insure the center of the spring reaches the correct temp.

God Bless,
J.D.

 

[BlackNet]

sure that's not 5150 instead of 6150?

 

[LRB]

TRS uses 6150 for springs and frizzens. They say so in their catalog. Manufacturers specs call for a 1650° quench heat, in oil. TRS recommends 1500° in a room temp water quench, with a 725° to 750° temper for a spring. I would follow the steel manufacturers recommendation, but that's just me. What TRS does apparently works for them. It's a judgement call. If I remember correctly, Jim Chambers uses the same steel for his springs, but recommends an oil quench. Water quenching is a risk.

 

[Erzulis boat]

Yep, the water quench is a no-go, at least for me.

I always order another set of spring castings from TRS on my projects, and I went 1500 with water and experienced cracking on any stock over .050" in thickness (TRS kit alloy)

I went to oil, and have had great success.....so far.

I don't have a lead pot, or a furnace. Since different alloys might indicate a bit different (color wise) what am I looking for on this alloy? Basically, am I going to just get it to color and try to maintain without going up a notch? I could go through this process multiple times to ensure a thorough soak?

This mainspring is so hefty, that if it "goes" in the mortise, there will probably be massive damage............yikes! Trust me, I have built a crude mortise to check function/reliability before putting it into this expensive walnut stock.

I have 2 of these critters-

 

[J.D.]

Wick is right on. Go with the manufacturers specs.

An acquaintance tempers springs by placing the polished spring on a 6" dia, 1/4-5/16 thick steel plate with a hole drilled for the diameter of the mounting lug, so's the spring will lay flat.

The plate is heated on a coleman camp stove until the the colors begin to form. The heat is cut back and the colors allowed to run slowly through the spectrum of oxidation colors, passing the deep blue into a light blue and gray. The spring is removed from the heat with forceps and quenched in light oil to stop further heating of the spring.

The spring is then slowly worked to insure that it is, indeed, springy.

I suspect that any old heat source, even a kitchen range or torch would do as well.

A good full color chart depicting temp ranges is available on the Anvilfire.com site.

From the main page, scroll down to Blacksmithing
in the 21st Century,or the Blacksmithing FAQ's.

Scroll down to "temper colors" near the bottom of the page.

God bless,
J.D.

 

[Erzulis boat]

Ok! Just got off the phone with TRS-

Had a great conversation, a TON of useful information on springs.

In a nutshell, the say a water quench works perfectly (26+ years) if the spring stock is heated evenly throughout.

They use Propane exclusively, as the correct color can be identified more easily, and heating is not so rapid as Oxy/Acetylene where it can "get away from you".

Tempering must go to a second blue, meaning that after it goes blue initially, you are in the 400's then it goes through another cycle and gets blue/black. This is the desired temperature. TRS says that going a little over won't hurt anything.

That being said, I am going to do one in water, and the other in oil- frankly, the water bit still scares me, but to be fair, my heat was probably not even.

The alloy used is 6150.

Potential mistakes-

Not getting the heat 100% even.

Too rapid to temp, and losing control.

Thanks Guys! I have a few techniques to try now, as I have about 20 springs to do right now. I really like the plate/stove idea.

 

[J.D.]

Did TRS say what kind of propane heater they use?
I haven't had any luck in heating parts to critical temp with propane without a forge, of sorts. I have stacked several insulating bricks to form a forge with propane torch as the heat source. It does take a while to get parts to the correct heat, so you will get a slow heat. An acetylene torch can also be used as a heat source.
However, don't play the flame of the torch directly over the springs.

A propane micro forge can be easily made. There should be a link to assembly instructions on the Anvilfire site.

Several springs can be tempered at once, using the steel plate and camp stove technique. Gotta be careful to not let those left on the plate get too hot as you are working with one.

The good thing is, if the springs come out too soft, they can be annealed and rehardened and tempered any number of times.

Annealing in a carbon rich environment, as when pack hardening will yield a full anneal without scaling.

One last thought, a 1/4-3/8 inch of oil on top of the quench water will reduce shock to the spring as it enters the water.

Good luck, and God Bless,
J.D.

 

[Erzulis boat]

Thanks for the info-

TRS uses the "Turbo Torch" (brand name) setup.

I have one, it is just a torch head assembly that goes directly on the smaller bottles and has a 1/2 or so opening, with a mixing vent about 4 inches back.

TRS uses 2 of these in unison and grabs the springs with needle nose pliers.

The "Turbo Torch" product has a nice big flame. I am going to dig mine out and give it a go with a Frizzen spring or two.

 

[LRB]

I have had much better luck using molten lead to temper springs, but one needs a temperature control. 6150 is a very fine choice for springs as it is very shock resistant, but requires a higher quench temp, and a higher temper temp than 1095. Although 1095 also makes a good spring. I am a bit surprised that TRS uses 6150 as a frizzen steel, rather than 1095, but they do recommend case hardening their frizzens. Might be economics due to their casting source, or steel source.