Tempering a Compression Spring

[HollowPoint]

For the most part I think I have it figured out but, I may be over-thinking the process a bit.

I searched online and found some oven-tempering recipes used with specific types of metals.

I plan on winding my own compression springs out of ASTM A 228 Music Wire. The tempering recipe calls for a thirty minute tempering time at 450 degrees.

Here's where I get a little fuzzy and I have some questions about the procedure.

(1) Do I preheat the oven to 450 degrees and then put the Spring in the oven for thirty minutes?

(2) Do I put the spring in the oven and turn it up to 450 degrees, let it reach 450 degrees and then count off the thirty minutes?

(3) If I allow both the Spring and the Oven to reach 450 degrees simultaneously, should I cut back on the tempering time by a few minutes due to the fact that the spring had already been exposed to near 450 degree heat by the time it actually reached the target temperature?

I'm probably over-thinking it but, having never tempered anything I was hoping for some input from someone who's been there and done that.

Short straight answers from those with hands-on experience would be more than welcome. Long winded lectures; not so much but, I'll take what I can get at this point.

I'm in the process of making up a slightly stronger Compression Spring to power my Daisy RedRyder BB gun. Right now I could probably spit BBs out of my mouth with as much velocity as I'm getting from the Daisy factory Compression Spring.

Thanks in advance.

HollowPoint

[Lee]

In a past lifetime, working for a commercial spring maker, we had ovens with a chain link conveyor. You set the oven temperature, let the springs fall off the spring making machine onto the conveyor belt and pass thru the oven. Oven length 5' or so, and conveyor speed such that a 5 minute or so trip thru the oven.
That said, and I'm no metallurgist, I believe that a preheated oven, put the springs in and "small springs, big oven, they'll come to temp quickly" so the 30 minutes should be OK. Our shop didn't call it tempering, but rather stress relieving, as we wanted to take out those stresses introduced into the metal by the spring forming process. The terms may be interchangeable. Just my $0.02 and I'm sure that a metallurgist will be here shortly ..... Lee

[HollowPoint]

Thanks Lee:

I seem to recall reading a couple of different writings along those lines whilst I was searching the internet for information about tempering.

Five or ten minutes either way may not make any difference at all once the 450 degree mark is reached by my oven. My reason for asking is that I just don't know and I want to make sure before ruining a perfectly good spring.

Thanks for your input.

HollowPoint

[M-Tecs]

The oven is always up to temperature before you put the spring in. This allows the temperatures in the oven to stabilize.

ASTM A 228 Music Wire is SAE 1086. This normally comes tempered and it will work without stress relief after winding. Per http://home.earthlink.net/~bazillion/finish.html the site states that “Spring wire that gets bent has to have the bending stress relieved”

That being said I cannot answer if stress relieving will improve the duty life of music wire as I have never tried it. I’ve made springs on Di-Acro spring winders, lathes and custom built hand winders without stress relieving them. Some of these springs went on production machines that have lasted hundreds of thousands of cycles without stress relieving

[HollowPoint]

The oven is always up to temperature before you put the spring in. This allows the temperatures in the oven to stabilize.

ASTM A 228 Music Wire is SAE 1086. This normally comes tempered and it will work without stress relief after winding. Per http://home.earthlink.net/~bazillion/finish.html the site states that “Spring wire that gets bent has to have the bending stress relieved”

That being said I cannot answer if stress relieving will improve the duty life of music wire as I have never tried it. I’ve made springs on Di-Acro spring winders, lathes and custom built hand winders without stress relieving them. Some of these springs went on production machines that have lasted hundreds of thousands of cycles without stress relieving

Hi M-Tecs:

This is great news for me. It means that I may be able to forgo any attempts at Tempering/Stress Relieving.

The thing that's throwing a monkey-wrench into my efforts is that fact that I'm getting mixed messages. Not from any of the guys here who've been kind enough to reply but, from the various articles I've read on the subject. (it could just be me misinterpreting things)

Some say that the type of Music Wire I'm using gets "Work-Hardened" when it's shaped into a spring so it has to be "Stress-Relieved/Tempered" otherwise it may become to brittle and fail prematurely. Others say that depending on the application, it may not have to be "Tempered."

And, still others get overly technical in their explanations in an attempt to hide the fact that they really don't know for sure so they seem to be extrapolating from what they've read on the subject.

I don't know either. I'm more confused about it than anything else.

I bought enough Music Wire to ruin three or four Compression Springs before I run out of wire. I guess I'll make and use the first one without "Tempering/Stress Relieving" and see how long it lasts.

With any luck my Un-Tempered springs will last as long as those production-application springs you've eluded to. Maybe I'm just over complicating my Spring Winding efforts.

I'll find out tomorrow. I should have my home made spring winder done by then.

Thanks for your input. I appreciate it.

HollowPoint

[Lee]

M-Tecs nailed it pretty much. And what I failed to mention was that not all springs get the stress relief/tempering treatment. Some do, and some don't.
Metallurgy Handbook might help. Or keep shouting on here and one of our resident metallurgists will come along to assist.
And no, I don't think you're reading too much in to the subject. It's a good question.

(I set up and ran old Torringtons, left over from WWII. But only as a fill in, as my primary function was Maintenance on the machines. So, I never really worried about many of the finer points. Always had an old spring maker to check with in case I needed assistance.......

[HollowPoint]

Thanks Lee:

Looks like I'll be trying my first Compression Spring without any "Tempering" or "Stress-Relieving."

Hope it works.

HollowPoint

[theperfessor]

Not an expert but I have done a little heat treating and know a little about metallurgy and material behavior. Tempering is primarily done after quench hardening to eliminate stresses caused by thermal shock and to turn incompletely formed martensite (a hard metastable crystal) into ferrite, a soft crystalline structure. The tempering your talking about when spring forming is designed to eliminate the internal stresses caused by the bending/forming process (which must occur at stress levels high enough to plastically distort the material) and is intended to prevent residual stresses from shortening the spring's life from fatigue.

I don't think the time is all that critical - you need to get it to temp and hold it there long enough for the residual stresses to be relieved, but not so long as to cause surface oxidation or waste your energy dollars. The biggest change occurs in the first few minutes, but probably 99% of what is going to happen will have happened during the first 15-20 minutes, and holding it at heat any longer does little beside waste your money and time.

The less severe the forming required to make the spring, the less need there is for stress-relief or tempering.

[HollowPoint]

"The less severe the forming required to make the spring, the less need there is for stress-relief or tempering."

What would be considered a "Severe Forming Process?"

I'm wondering if smooth rolls over a half-inch mandrel fall into this category. It somehow seems that sharp bends in the forming procedure might be considered "Severe Forming."

I guess I'll find out soon enough. I finished up my winding tool; just need to drive to the hardware store to pick up a couple of 10x32 screws and I'll be ready to wind some wire.

HollowPoint

[uscra112]

I've wound more than a few springs on my lathe, using "piano wire". Never even occurred to me to stress relieve 'em. Never had one fail.

I've done even more wire bending for model airplanes, often needing very sharp 90 degree corners. THOSE can crack easily, and I suspose might benefit from stress relief. I just learned to avoid bend radii less than 4x the diameter of the wire.

[RayinNH]

Keep in mind that your oven dial may read 450 but that doesn't mean your oven is delivering that...Ray

[theperfessor]

One of my favorite engineering textbooks is "Machine Design An Integrated Approach" by Robert L. Norton. In the chapter (13 in the 2nd Edition) on spring design he has a table that shows that A228 Music Wire is the equivalent of AISI/SAE 1085, which is a plain carbon steel with approximately 0.85% carbon content. A description says "Toughest, most widely used material for small coil springs. Highest tensile and fatigue strength of all spring wire. Temperature 0C to 120C"

Based on the wire diameter, another chart shows that the ultimate strength varies based on diameter, with 0.012" diameter having an ultimate strength of about 370,000 psi, going down to about 225,000 psi for 0.200" wire.

I'm not sure what the number would be but "severe forming" is most likely defined as some ratio of bend diameter to wire diameter. uscra112 used a 4:1 ratio and that sounds reasonable based on his practical experience.

One thing you might want to do is close the ends of the springs and then grind half of the last coil flat so the end of the spring is square to the central axis. Think of a valve spring from an IC engine. A spring that contacts just the end of the spring wire creates higher stresses in the first coil than anywhere else in the spring.

[theperfessor]

For what its worth, I think you're on the right track to just give it a try and see what happens.

[HollowPoint]

I tried winding a couple of springs this afternoon. The first one was a total failure. All I managed to do was bend the holy-krapp out of one end of my music-wire.

The second attempt was much better but still not that good.

The mandrel I used was sized the same as the guide-rod on the BB gun. It turns out that when the winding pressure on the music-wire is released, the inside diameter of the finished spring opens up substantially.

I'll have to turn down my mandrel on the metal lathe about an 1/8" and then try again. That should give me the exact inside diameter when I release the tension on the wire.

Another problem I encountered was my assumption that I'd bought enough wire to do about four separate springs. NOT.[smilie=b: I bought two thirty-six inch lengths thinking I had enough wire to screw up my first few attempts before making a good usable spring.

On my second attempt I found out that one thirty-six inch length of wire wound over a slightly oversized mandrel gave me a Compression Spring that was a full inch shorter than what I needed.

I learn these things the hard way. I'm hoping I'll be able to get the exact finished length I'm needing once I reduce the diameter of my mandrel. If not I'll have to shell out for a small roll of music wire.

That second spring I made was good enough that I actually installed it in my BB gun just to see what would happen. I shot two BBs out of the gun with my home made Compression Spring and it worked but, I could have ran to the target faster than my BBs were flying to the target.

Before installing my home made spring it measured six and a half inches long. The factory spring is seven and a half inches long on one of my Daisy BB guns and eight and a quarter on another. ( I own two of them)

I fired only two shots then removed the home-made spring and re-measured it. It measured six and a quarter inches after firing only two shots. I'm wondering if I'd fired more shots would it have shrunk down even further; and, is this a sign that maybe these spring will need tempering or stress relieving after all?

When I get a little more free time I'll drive down to pick up some more music-wire. In the mean time I'll do a little tweaking to my winding tool. The tool itself worked but, with a couple of small modifications it should work a little better.

Looks like I may have to Temper my home made Compression Springs after all.

HollowPoint

[RayinNH]

Have you tried to take the Daisy spring and pulling on it to make it longer and thereby increasing its strength? How about just ordering one from McMaster-Carr?

[HollowPoint]

Hi Rayin NH:

I did both those things.

On the MacMaster Carr website I couldn't find a spring close enough to the dimensions I'm needing. I even drove down to my local Ace Hardware store to look through their spring selection. No luck there either.

I thought about buying enough of the shorter springs of the proper dimensions and weight so that I could maybe stack three of them together to give me the right overall length but, a little more research showed me that this wouldn't work either. Stacking shorter springs of the same strength generally cuts the over all power of the spring by a third. ( or so I've read)

I did the spring-stretch thing initially; once I found out just how short the factory spring was. In fact, just before reinstalling it this last time around I stretched it again. (from 7 1/2" to 8 1/2")

Stretching the factory spring does give me higher velocities but, only temporarily. After a few shots the spring tends to shrink back down to near its original length. I'm afraid that repeated stretching and shrinking will result in the premature death of the spring.

This is what prompted me to try to make up my own replacement spring. I haven't given up just yet. Even the two krappy home made springs I've made thus far has proven to me that it really is possible to make my own replacement spring for these Daisy BB guns. I just have to fine tune my spring making procedure.

Thanks for your input. I appreciate it.

HollowPoint

[Lee]

Quick and dirty generalizations:

larger pitch = more force

larger dia. wire = more force

all for a given spring diameter and length.


Stretching does make them "stronger" but as you have found, they soon "relax" back down in length, and strength. Stretching works best when you only stretch a little bit, and the spring is only compressed a little bit. Never looked inside a Daisy, but I would not be surprised to find a considerable amount of spring compression occuring.

[RayinNH]

Hollowpoint, can you post all the pertinent information about this spring, length, I.D., wire diameter...Ray

[HollowPoint]

Quick and dirty generalizations:

larger pitch = more force

larger dia. wire = more force

all for a given spring diameter and length.



I came across this general information when I first started researching this topic. I've used that info to design my new spring.

The factory spring I'm replacing had an inside diameter of a fraction less than .5". The wire diameter is .090" and the overall length of the longest factory spring I've measured is 8.5".

I'm using 3/32" Music Wire to make my new spring. It measures a hair over .090" so that gives me a slightly larger wire diameter.

The space between each of the factory coils is about .250". I made my Spring winding tool so that the space between the coils is a little over .300".

When these BB guns are in the cocked position. The Compression Spring is almost fully compressed. I have another Daisy BB gun project going right now that's listed in the "Special Projects" forum. It's titled, "Driving Miss Daisy." On that post there's a link to a website that has a cut-away view of this BB gun's internals. Take a look if you get a chance. It gives an excellent view of how these BB guns work.

http://www.daisycollectors.com/forum/showthread.php?tid=58

I mentioned in my previous post that I was going to tweak my Spring Winding Tool and turn down the diameter of my mandrel before attempting to make any new springs. Well, I finished up my scheduled work early today so I did the tweaking and I turned down my mandrel.

Since I'd already ruined my first piece of Music Wire I went back and set everything up to give it another try with the damaged piece of Music Wire.

Good News and Bad News. The good news is that it worked perfectly. I ran the damaged piece of wire through the tool and the end that I had bent all to heck got ironed out as it ran through the tool. I ended up with a spring just a tad over ten inches long.

The bad news is that I had turned down my mandrel just a tad to much. When I released the tension on the newly wound spring it opened up but, not enough to slip over my BB gun's guide rod. Not without having to push real hard to get it to go on.

While I was fishing around in my junk-drawer I found a piece of metal that's the exact size I'll be needing to give my springs the correct inside diameter. I wished I would have found that piece of metal before I went through all that trouble.

I think I'll reduce the space between my coils just a hair more before trying to make any new Compression Springs. The combination of that reduced space and the correct sized mandrel should give me a Compression Spring right at the eight to eight-and-a-half inch mark using a 36" piece of wire. That would be perfect for my needs.

I've kept the test springs I've ruined up to now. Once I get one that's worth bragging about I'll post some pictures of all of them.

I'll keep chipping away at it as time permits.

HollowPoint

[MtGun44]

Try this.

Heat the wire red hot and let it cool naturally to anneal it, then wind it. Then heat
red hot and drop in water.

THEN temper in oven to 500F for about 15 minutes.

If it cracks, temper the next one at 550F.

Winding it cold works it more than needed and likely will be a LOT more difficult than
winding it annealed.

I have NOT done this and this is based on understanding heat treating, but no personal
experience making a spring this way. If you have the failed previous wire, nothing lost
trying it with your junk wire.

If the spring tends to collapse, reduce the tempering temperature. If you do NOT temper,
just heat red and water quench you will have a hard spring and probably to brittle to survive.
Tempering trades hardness for ductility. Too high a tempering temperature and it wll be
too soft, but never crack.

Bill

[HollowPoint]

I finally got all my ducks in a row with the Home-Made replacement Compression Spring project for my Daisy RedRyder
BB gun.

I know these BB guns are made for little kids and backyard plinking but, I wanted a little more out of my BB gun than the sorry 264-5 FPS velocity I was getting out of the box.

By modifying the Transfer Port I was able to get another 20 FPS out of it but that was still way to slow for my liking so I went about figuring out how I might make my own Higher-Powered Compression Spring in order to bring my velocities up to at least the 350 FPS stated on the box it came in.

I did a little informal research on how to make a Compression Spring. I asked around about how to Temper/Stress Relieve my Springs after winding them. I thought about buying a Universal Spring Winding Tool but, at sixty-five-bucks plus shipping I opted to make my own dedicated tool.

I've changed the Compression Spring on this particular BB gun at least a dozen times and I found that the stronger the Spring, the more the foul-language-factor applies.

The last two Compressions Springs I made were alot stronger than the factory springs.

In this case I'm thinking that the word, "Tempering" refers to the fact that I lost my temper whilst the metal of these Springs gained its Temper.

I wanted to install the longest of my last two Home-Made and Tempered Springs but, it was just to hard for me to do, so in the end I had to settle for installing the shorter of those two springs; and even that was a chore in itself.

I still want to install the longer Spring but, I'm going to have to make up a Spring-Compression-Jig in order to do so.

I found that when I made my replacement Springs with the space between my coils (pitch) only slightly larger than the factory springs I'd get higher velocities but, only for a short time. After the Spring settled-in the velocity would drop down again. It was still higher than the factory velocities but, the new Spring just wouldn't retain the higher velocities they produced within the first five shots or so. (these were test runs on untempered springs.)

I've fired about a hundred BBs out of my RedRyder with the Shorter of the two Home-Made Tempered Springs in place and thus far the velocities seem to be holding steady at the 350 FPS range. I'll shoot it a couple of hundred more times before I chronograph it again.

When I go to install the Longer Tempered Spring I'll measure the Spring I take out just so see if it's shrunk while I had it in the gun. I'm sure it will have shrunk a little. They all do over time but, finding out just how much will be a good indication about how much I need to tweak my next replacement Compression Springs so they retain their power and velocity as long as possible.

Below are a few pictures of the trials and tribulations of this project. I hope you all can glean some good information out of them and maybe enlighten me with helpful information I might be able to use the next time I make up some new springs.

HollowPoint

[HollowPoint]

It's been about a week since I installed one of my home made Compression springs into my Daisy BB gun.

A little over two hundred more BBs shot and it's still spitting BBs in the 350 FPS range. Even the cheaper Copper-Head BBs are moving along at a pretty good clip. The premium Avanti BBs seem to have a better fit in the bore so the velocities are just a hair above 350 FPS.

Mission accomplished; making lots of cat food.

HollowPoint