Spring information

[Joe S]

Jim

Can you recommend a book or other source that gives spring temper information for various steels?  I have looked and I can't find anything useful. Thanks.

Joe

[Jim Kibler]

Well, the best advice I can give is to shoot for a hardness of about 45 HRC.  Perhaps a few points less rather than more.  When you've decided on your steel to use, do a search for a tempering temperature (tempering curve or tempering chart) that will yield this hardness.  Temper at this temperature.  I don't really know what to suggest as far as books.

All the best,
Jim

[Bob Roller]

Bob I use to wonder the same thing. How they did it without a pyrometer or a furnace. Once I was working on an original English lock and was studying the tool marks and such for clues. On two different locks I noticed  that there was some lead in between the leaves of the main springs. That was the clue that led me to the lead bath tempering method. Lead melts at about 625F. So for a long time I used that method. I use to set the lead pot right in the forge.  I also noticed that on some broken springs there was visable layers of the steel. I think some gunsmiths made their own cruciple steel for springs.

Jerry,
I have in years long gone tried most of the tempering methods including the
molten lead.After I got some 1075 from P.I.Spence of Marietta,Ohio in 1957
and having watched George Killen here in Huntington draw to a color I settled
on that material and that method and I think over 50 years of successful lock and trigger making
has proven,at least to me that I did use good material and a reliable method.
I have no oven or pyrometer but do have a lot of spring making experience.
At this point in time I am concentrating on double set triggers and am happy
with the results and sales thanks to this forums readers.
I have lead but seldom melt it and even with a new AC it heats up the shop
more than I want.

Bob Roller

[David Rase]

Good news, my long awaited ( 6 plus weeks) new heating element for my heat treat furnace is being delivered today.  Time to normalize the spring, finish up the file work, and get to hardening and tempering.  Hope to see this project wrap up this week. 
David
Below is a photo of the work in progress.

[45-110]

Your picture explains all the hours you have in it. Its beautiful. Good luck with the heat treat.
kw

[jerrywh]

Bob. I have used the color method a lot and after one learns how to do it it works pretty good.
 And have used the lead method a lot because back then ,20 some years ago, I never knew a better method. When I use the color method I temper to a blue gray color and do it twice. The method I have the least confidence in is frying in oil. in the 1960s I knew a gunsmith who used the frying method exclusively but he had a high degree of failures and he finally paid me to make his springs for him. The other gunsmiths started buying my springs. Most of the springs I made then were shotgun mainsprings and top lever springs for double guns.   I usually made a dozen at a time. at first I had about a 15% failure rate and so I found a heat treating engineer and he told me what I was doing wrong. It was the time element. Also I was getting a lot of faulty steel from a supplier in Portland Oregon. Some steel suppliers will give you info on tempering springs if you request it. But all springs are not tempered the same, like coil springs so you need to be specific when asking. You probably know all this but maybe it will help  some of the other guys. 

[D. Taylor Sapergia]

Jerry, I really like your analogy of the spring as a cookie in the oven...even though it looks nice and cooked on the outside, doesn't mean that the inside is cooked.  Similarly, your spring may have a beautiful blue on the outside but the inside hasn't reached that temperature yet.  So the soak AT TEMPERATURE is vital.

[LRB]

  A properly tempered spring will have no real colors. The heat range for good temper leaves only a gray neutral color.

[David Rase]

I have never been able to use the color method due to my lack of being able to distinguish shades.  I can see primary colors but not shades.  Been a hurdle for me all my adult years.
David

[Joe S]

Jim

I followed your advice, and found a couple of references for tempering temperature and hardness for carbon steel. According to the chart in anvilfire.com, HRC 45 is reached at a temperature of 630^o (F), so just above blue.  According to Heat Treating Data Book - 10th Edition E-Book - Seco/Warwick, HRC 45 is reached at 900^o. Also, per the latter reference, “a typical steel spring has a Rockwell hardness of 38 … on the C scale”. This implies a tempering temperature of 800^o on the anvilfire.com chart, and about 950^o in the latter reference’s chart.

I don’t feel like I’ve learned anything. Folks on the ALR site apparently make functional springs at temperatures of about 570^o (blue) to 800^o, with carbon steels ranging from 1070 to 1095.

I’m a little bit baffled as to why spring tempering information is so difficult to come by. This is not rocket science.  It would be very simple to do the basic testing, and write a single equation for hardness as a function of tempering temperature for all of the relevant carbon steels.  Then hardness could easily be related to the various spring characteristics, such as yield point and fatigue limit. I’d think that this information would be in a Metallurgy 101 textbook somewhere, but I can’t find it.  Even my old standby Machinery’s Handbook isn’t helpful.

It seems to me that Jerry Huddleston remains our best source of knowledge on this topic.

[jerrywh]

Jose Gordo.
   There is a good chance that the differences in temperatures can be explained by the type of spring they are referring to and then again it could be due to what I said before about not believing everything you read in books.  The low temps given for temper could be for coil springs and the high temp for leaf springs. After years of trial and error myself as well as other good spring makers have mostly decided on a temp for V springs of between 720 and 800°F and retain that temp for at least 20 minutes. It is a pain in the rear end to melt a lead pot for one spring but it is better than making a new spring.  Lead melts at about 625°F but in melting a pot of lead the bottom of the pot reaches about 750 or 800 before the top is melted then shut off the heat. The spring should be held under the surface until the lead re hardens. This will take care of the time factor. Then re heated until the springs pops to the top. Then you can take it out of the lead and rap in on a wooden block a couple of times, that will knock off most of the lead. The spring should be smoked before putting it in the lead to prevent the lead from sticking to it.

[Jim Kibler]

Jim

I followed your advice, and found a couple of references for tempering temperature and hardness for carbon steel. According to the chart in anvilfire.com, HRC 45 is reached at a temperature of 630^o (F), so just above blue.  According to Heat Treating Data Book - 10th Edition E-Book - Seco/Warwick, HRC 45 is reached at 900^o. Also, per the latter reference, “a typical steel spring has a Rockwell hardness of 38 … on the C scale”. This implies a tempering temperature of 800^o on the anvilfire.com chart, and about 950^o in the latter reference’s chart.

I don’t feel like I’ve learned anything. Folks on the ALR site apparently make functional springs at temperatures of about 570^o (blue) to 800^o, with carbon steels ranging from 1070 to 1095.

I’m a little bit baffled as to why spring tempering information is so difficult to come by. This is not rocket science.  It would be very simple to do the basic testing, and write a single equation for hardness as a function of tempering temperature for all of the relevant carbon steels.  Then hardness could easily be related to the various spring characteristics, such as yield point and fatigue limit. I’d think that this information would be in a Metallurgy 101 textbook somewhere, but I can’t find it.  Even my old standby Machinery’s Handbook isn’t helpful.

It seems to me that Jerry Huddleston remains our best source of knowledge on this topic.

Tempering temperature to get a hardness of 45 HRC varies with alloy or grade of steel.  For example, 1040 steel might be in the range of 600-700F but O1 steel would be closer to 1000F.  A simple process to follow:

Pick a grade of steel suitable for springs
Look up the recomended hardening temperature and quenching procedure.  Use this.
Look up the temperature to get around 45 HRC and temper at this temperature.  Hold at temperature for 15-20 minutes if possible. 

You're done.

I agree that there is a load of misinformation about heat treating springs. 

Good luck,
Jim

[FDR]

JOSE: here is the "Bible" on heat treating carbon steels. Everything you ever wanted to know!

https://www.amazon.com/Heat-Treaters-Guide-Practices-Procedures/dp/0871705206/ref=asc_df_0871705206/?tag=bingshoppinga-20&linkCode=df0&hvadid={creative}&hvpos={adposition}&hvnetw=o&hvrand={random}&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl={devicemodel}&hvlocint=&hvlocphy=&hvtargid=pla-4583932700242497&psc=1

Expensive and very technical! 

Just ask a  retired knifemaker.

Fred

[shortbarrel]

I make springs out of Model T main springs. Never had one to break or take a set. If you go by the rules of hardening and tempering.Henry Ford bought the best steel he could get.

[Joe S]

Jim - Thanks. I will follow your advice.

Fred - I'm curious, but at $349 a copy, I'm not that curious.  I'll see if the library can get it for me.

[Pukka Bundook]

Jerry,

That is a good tip, to smoke the spring before dropping in the lead pot.
I have always had some lead stick so will do it your way now.

Many thanks,
R.

[FDR]

Fred - I'm curious, but at $349 a copy, I'm not that curious.  I'll see if the library can get it for me.

Jose: I have a copy of the second edition from 1982 when I started in the Knifemakers Guild. It is as advertised, everything you want to know about heat treating with charts on a variety of steels including all the common carbon steels. There is also one title "Tool Steels" by Roberts and Gray, from the same source, that is quite interesting. I have that one also.
I decided early on that to maintain the high level of quality in my knives I would send them out for heat treat. Paul Bos, the heat treater for Buck Knives, must have heat treated most of the Guild members knives at that time. They always came back individual blade certified and perfect. Over 400 knives and only one ever returned and that one for a handle material problem.

https://books.google.com/books/about/Tool_Steels_5th_Edition.html?id=ScphevR_eP8C

Fred

[shortbarrel]

The above me post above me said it all. Thanks

[msellers]

Jim - Thanks. I will follow your advice.

Fred - I'm curious, but at $349 a copy, I'm not that curious.  I'll see if the library can get it for me.

Try here, definitely more affordable.
https://www.thriftbooks.com/browse/?b.search=Heat%20treaters%20guide%20practices%20and%20procedures%20#b.s=mostPopular-desc&b.p=1&b.pp=30&b.oos

[Daryl]

I noted with interest, Jerry's mention about smoking the spring to prevent lead from sticking (soldering) to it.
What I do with my lead bullet and ball moulds, is to spray then with MS Moly bullet coating spray, while I still
had some, but now that it is gone, I use Lyman Super Moly Spray Lube. It coats the moulds, and prevents lead
from sticking to them. It will do the same for springs & in no way effects them, other than you will not see colours
through the coating. Pretty sure, the thickness of the coating is not measurable.