Spring tempering question

[Joe Sullivan]

How do you temper your springs? This is a stumbling block for me. :idunno:
I've broken 5 springs trying to get this. At 4 hours each I'm reaching burnout. I made another set and I'm scared to try loading them.

I tempered these with a propane torch. I watched them go thru the colors and stopped at blue/gray.
Is this method just softening the surface because the ones I broke had a shell different colored than the interior.
Should I taper the thickness more?

 

[MikeyC]

Sounds like your tempering temp is to low. Blue starts appearing at 580f. You need to get to 700f for a successful temper.
Couple of ways to do this. If you or a friend casts bullets, you can heat the lead to 700 and fully soak the spring. Or a shallow pan filled with motor oil ignited with a torch and left to burn will also give about 700f.
Are you using a 1070 to 1085 steel or something else?
Your springs sound to brittle, hence the cracking.
Mike C.

 

[JohnN]

I've never had much luck at this. Not sure if an ordinary propane torch is hot enough. You might want to pick up Kit Ravenshear's booklet "Simplified V- Springs" from Track of the Wolf.

 

[jdkerstetter]

That's great advice. Kit's little books are a valuable resorce and cheap.

White Rabbit, From your description, my best guess on the cause of your problem is that you are not holding your springs at tempering temperture long enough for full saturation....the outside is tempering but the inside is remaining brittle.

Tempering with a torch is hit and miss as it is hard to hold a part to a constant temperture long enough with the high heat of a flame. That is why most who temper a lot of metal perfer to have a dedicated heat treating oven.

Good Luck, J.D.

 

[Joe Sullivan]

The first set I made, I quenched in oil and they snaped like glass. The second, quenched in water and tried tempering in the coal fire. they snaped.
The third I quenched in water, then toaster oven at 450 deg. for an hour. I only broke one. I'll try boiling it in oil like MikeyC said. I used auto leaf spring on the first ones and then mower blade on th last 3. I don't know what the material is except it's not hot roll.
jdkersetter; I can see the differance between the inside and the surface. Boiling in oil is the next step, I guess. I need to order some cold blue from TOW so I'll order the book.
Thanks for the advice guys.

 

[LRB]

Pretty much what was said about the heat. Not enough, and not long enough. Since you are forging these, you will get more strength if you normalize them before the hardening quench. This will reduce the grain size and make the grains more uniform. In very dim light, heat the spring to a bright red-orange and air cool. Then heat a little past non-magnetic and air cool. then again a bit shy of non-magnetic and air cool. Then heat evenly to a bright red to red-orange and quench in warmed canola oil. Your best way to go would be the lead bath at anywhere between 700° and 750°, but you really need to know the accuracy of the temp of the lead, and it would be good to soak at temp for maybe 20/30 minutes. That will give you a fine spring if you have the means to do it. Access to a HT oven would help immensely.

 

[MikeyC]

Forgot to add, I've never had any luck using a propane torch. Maybe others here have. But it would be very hard to get your entire spring to an even temp.
Lee used to make an inexpensive lead thermometer for use in their melting pots. Just a thought.
If memory serves me right, you want to draw back to 44 to 50Rc.
What I would do is just make some simple flat or slightly curved springs and draw them to where you think is about the right hardness. When you perfect that, then I would move on to your more complex shape.
Also not all steels will give off the same color at a given temp. O series and D series are a prime example.
Knowing exactly which steel you are using would help a lot.
Embrittlement can also be caused by not cooling quick enough from your draw temperature, just another thought.
Mike C.

 

[dave_person]

Hi White rabbit,
I make a lot of springs. You may be hardening the steel too much and not tempering long enough. I use an electric burn-out oven to temper springs. I first harden them by heating to bright cherry red and quenching in water with about 1/2 inch of transmission oil floating on the surface. That gives me the hardness I want when using steels such as 1075 and 1095. Then, I heat soak the springs for 1 hour at 710 degrees in my oven and let them cool slowly in the oven.

Kit Ravenshear's method of tempering works as well. Place the hardened spring in a metal container and cover it with motor oil. Outside, ignite the oil with a torch and let it burn off. Remove the spring and let cool on a block of wood. Oil burns at about 750 degrees, so you essentially create a little oven of burning oil at about that temp that heat soaks the spring for 10-15 minutes. I found his method produced workable but somewhat soft springs. I prefer to use my oven.

If you have a lead melting pot, you can melt lead and place the hard spring in the molten lead for 30 minutes to an hour and then remove and cool on a block of wood. If you have a melting pot with a thermostat control, set it for about 700-750 degrees.

dave

 

[Joe Sullivan]

Wow! Loads of infomation guy's. Thank you. I just finished boiling them in oil. I should have a lead pot but I don't. I guess I'll have to get one. I built a waste oil foundry furnace but have no thermostat yet. It'll take me a while to absorb all this info. I've been polishing the lock parts and the barrels. Tomorrow I'll assembly them and see if I can get the springs to load.
Dave; I've seen the oil method and thought I mite try it but this guy "boils" them in oil. I did it just like he did.
check this out
Anyway thanks. I'll let you know :thumbsup:

 

[matt denison]

I just finished boiling them in oil.

Nope. He is not boiling the springs, he is burning off the oil which burns at about 700 - 750 degrees. If you didn't set the oil on fire and let it burn out by itself then you are likely to break those springs too.

 

[Joe Sullivan]

I used a large tuna can, put the springs in and filled over the springs, proped up the can on 2 bricks and put the torch to the bottom. After it boiled for 10 minutes it flamed up. I boiled with flame for 20 more minutes or so and pulled the torch away and it burned for another 10 minute.

 

[ohio ramrod]

I find that I have the best results tempering springs by wrapping them with aluminum foil, and placing them in a electric lead pot filled with just melted lead for about an hour. I "hold them down" with a steel rod! Remove and let air cool while still in the aluminum foil. :idunno:

 

[raszpla]

here's a simple diagram of the furnace to heat the springs.

I see that you do not understand and do not differentiate between, systems of work springs.

I do not know English, but I can think of something and I'll explain later :hatsoff:

 

[LRB]

That really isn't quite an ideal temper heat for a hard working, high flex spring. lead melt is about 625° to 630° depending on purity. Your target temp is 700° to 750°, or somewhere in between. Your heat works for some spring applications, but is slightly brittle and more subject to failure for others. Not saying it will fail, just that there is a greater risk that it might. Also depends on the steel, and how it may have been prepped. You don't really need the foil, just smoke the part and the lead won't stick.

 

[Joe Sullivan]

I have furnaces But no thermostat yet. The top one's built for a Mako propane torch which should make 1600 deg. I was firing the clay in this photo using the W.O. burner. The bottom one burns waste oil and will go 3500 deg. if I don't stop it.

Mako propane torch

 

[Fauquierfarmer]

I will add to previous comments-a handy method for tempering small parts is to use the concave bottom of a soda pop can. Place the part in the "dish", fill the dish with motor oil adding a little lighter fluid to aid ignition.Ignite the oil with your propane torch and let it burn up completely.
When it cools, you have a spring.Works particularly
well for tempering powder flask springs.If the resulting spring is too soft, its usually due to failing to heat the part to a dark red during initial treatment.

 

[jdkerstetter]

In his defense Wick, lead can be heated well past the melting point. As long as he has a thermometer and not just using the melting point as an indicator, 700-750 dergrees is easily attainable.

Enjoy, J.D.

 

[jerrywh]

When tempering steel there is a time factor. First let me say. Any carbon steel of 1075 to what is called 01 will make a good spring if it isn't flawed to begin with. Before hardening a spring heat it to a red heat and observe it to see if you can see any bright red lines in it. An external flaw will show up as a bright red or orange line much brighter than the surrounding metal. Do this before you even begin to forge the spring. It will save you a lot of work. Much new spring steel is flawed. Believe me. I do this for a living.
As for the time factor, Tempering temperatures must be held for 12 minutes for every 1/8" of thickness of the metal being tempered. Think of this as cooking a biscuit. You can’t just heat a piece of steel up to 725° and stop because it is not done on the inside.
You end up with a spring that is tempered outside and glass hard in the middle. OK.
Put the spring in your lead pot and heat the lead until it melts. Hold the spring under the lead until it sets up with a piece of wire or something. Then reheat the lead until the spring comes floating to the top again. When it does, remove the spring and knock off any lead that sticks and let it cool naturally. Don’t quench.
This is only if you don’t have a tempering furnace. If you have a furnace heat to 725° F for 20 minutes, remove and let it cool. There are other ways to accomplish the task but I have found these to be the best. PS-- The guys are correct about lead melting at too low a tempurature. The best way to compensate for this is to buy a lead thermometer for $30.00 at midway or some someplace. Just googe it.
Let the argument begin. Again.

 

[Zonie]

I would shy away from using a water quench from the red heated condition and recommend using a thin oil like ATF pre heated to 120 degrees F.

Water quenching will often cause cracks in the spring material and if a crack forms at this stage, all of the fancy tempering in the world won't keep it from breaking.

The only possible problem with using a warm oil quench from the red heat temperature is it may not bring the steel up to its full hardness.

As we are talking about springs and not cutting tools, having the steel at its maximum hardness prior to tempering should not cause a problem.

 

[LRB]

I know, but the way he worded that post makes it seem that he is useing the lead bath just at the melt temp.