Trouble Creating a Very Small Gun Spring

[bthomasv]

Ok I am stuck. I need some help from someone who has experience making gun springs. But not just gun springs, very SMALL / THIN springs.

To get it out of the way up front. I have successfully made obsolete gun springs before. This is a very old gun (Hood International No. 3, .32rf). No replacement springs are available for it anywhere, trust me I have looked. I am starting with flat tempered spring material purchased at this thickness.

I believe my issues revolve around holding such a very small spring while trying to go through the production steps after grinding/filing to size:
1) Heating and bending to dimensions (MAAP Torch)
2) Heating and quenching (MAAP Torch + Brownell's Quenching Oil)
3) Tempering (Lead milting pot)

While I understand that I do not know everything about spring making, I believe my issues surround the extremely small size of the spring. This is more like a watch spring than a gun spring in size. My results after several attempts are springs that snap upon use or when testing before use. I believe because the size is so small, that I am not getting even heating of the metal. On this small spring I have trouble with:
< Not able to bend the metal into a shape quick enough before the item has cooled (Causing Stress)
< Not evenly heating the spring to cherry red prior to quenching (Portion I am holding does not get cherry?)
< Possibly not heating the spring evenly during tempering (Have to hold it somewhere, right?)

I understand all these thing are basic, but I need some ideas on how to accomplish this on a spring so small that holding it anywhere causes that surrounding area of the spring not to heat sufficiently. This seems to result in stress in the metal causing breakage in usage after a few cycles, or even before it passes initial test bending.

To understand the small size, here are the finished spring dimensions:
.017" = Spring Thickness
.070" = Spring width
I have also attached a diagram of the spring in its 3 positions: Static, minimum installed compression, & fully compressed.

Thanks for any suggestions,
Bruce

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[Forger]

If you lay the spring on a larger piece of steel. Then heat from below until it gets to the critical temperature. Hopefully this helps.

 

[Ura-Ki]

Try setting the spring on it's side while heating, then, instead of trying to pick it up, quench it right there on the heating surface by pouring the oil directly on it as soon as you remove the heat! Don't try with a jewelers soldering stand, use a fire brick or something like that! I use old scraps of marble stone I find around, they usually have a porous surface that makes heating much more even, same as a fire brick!

 

[bthomasv]

Thanks, I will try that. What about making the 90 degree bends in this small a piece? The spring is so..... small that it cools in about 2 seconds. More time then it takes me to lay the spring in place and bend it?

 

[jbett98]

Have you tried looking around for other pistols that were made by Hood using different names. Maybe they used the same parts.
Or, try talking to a watchmaker for some expertise in spring making.

Suicide Specials

suicide specials

gun-data.com

 

[Ura-Ki]

Is it possible to do the 90 deg bends first? If so, you could do the bends with out it really cooling before heating to the full and finishing the larger bend before quenching!

Or, you could make a forming block/mandrel that could do all the forming steps while heat treating, not sure how small this spring actually is, but a couple scraps of steel to make forming tools shouldn't be too hard!

 

[RVTECH]

Would steel 'banding' strap material work for this?

I have used it over the years to make flat springs for a few application (one gun) and it worked well and no heating required to make bends in it.

 

[bthomasv]

The width of the spring is about the thickness of a quarter. The thickness of the spring is about the thickness of 6 pieces of tablet paper. Very, very small and thin. Consequently, because of how thin, it cools almost immediately after being removed from the heat source. Makes it very hard to bend 90 degrees while still hot enough..............

 

[Ura-Ki]

For heavier flat springs for firearms, the old garden rake tines work very well!

 

[po18guy]

Maybe a pair of the round-jawed beading pliers. Keep the heat on with one hand while rolling it with the rounded pliers in the other?

 

[chukar]

This is fascinating.

I'm spitballing here but pre-make the 90 degree like the other dude stated and leave a generous amount of material off of the bend. An orthodontic 3-prong plier will probably give you a "tighter" bend rather than a civilian plier (no offense). Build a jig for the radius of the spring that you need. Hold with your tag end and make a tension device for the other end unless you have three hands or a willing friend and heat away and keep the cooler nearby and when you are confident dump oil on it instead of dunking. I would make sure that the flame is off... Proceed on.

I would honestly tell you to find a metallurgist to as for advice.

Idaho, UN Reno, etc.

I bet someone would be willing to help you.

 

[Ura-Ki]

Actually, a pair of medical staple pullers might do the trick, a visit with your doctor or veterinarian might net you a pair or three, might have to pinch the jaws tighter together, but they might handle the 90 deg bend super slick!

 

[dangerranger60]

What you need to do is anneal the metal, cut and bend it to size and then harden it. That way you are making your bends in soft steel.
I used to get my spring material from old wind up clocks or the heavier springs from the recoil starters on lawn mowers. Good Luck DR

 

[billdeserthills]

Any chance you can use a piece of spring steel wire? Much easier to work with

 

[Capn Jack]

Last time I needed a spring like that, I used a woman's hair pin.

 

[ZigZagZeke]

What you need to do is anneal the metal, cut and bend it to size and then harden it. That way you are making your bends in soft steel.
I used to get my spring material from old wind up clocks or the heavier springs from the recoil starters on lawn mowers. Good Luck DR

I once worked in a steel mill where we produced everything from nails to piano wire. This is good advice. Make your bends while the steel is soft, then harden it in an oven environment where you can heat evenly and control the temperature.

 

[P7M13]

I see a spring that would be made using a four-slide type forming machine where the material is formed from non-tempered material and then heat treated.
What @dangerranger60 suggests is spot on.
Some ideas:

• You're looking for hardening that is consistent through the material. That means crystal phase formation of the preferred structures, which means time and consistent heat.
• Suggest you find a small kiln. If you weren't in KCMO, I'd offer one of mine for you to try.
• With a model made out of soft steel or tin that is formed to the exact dimensions, make a carrier out of kaolinite or another high temperature clay to hold the spring in shape when you heat it in the kiln.
• On an aside, depending on the steel composition, you may want to put it in the carrier and then cover it with charcoal dust. Yes, it will burn off over time, but some carbon will migrate into the steel structure, helping with hardening.
• When the temperature is right, pull the whole carrier out of the kiln, tip and dump the spring into a coffee can with waste oil. Sure, it will flash-burn for a second. Pull it out a short while after.
• Then wash it, dip it in acid, and instead of lead as an annealing medium, use NaNO3 molten salt. You will then get some nitriding action out of it.

sounds like a fun project. Good luck!

 

[Stomper]

Aside from the thrill of conquering a technical challenge, it sounds like it'd be easier and cheaper to just grind the gun up and call it a day!

 

[coop44]

Speaking of orthodontists, they use a thin flat wire don't they?

 

[bthomasv]

Thanks for all the responses so far! I have a love/hate relationship with forums. Half the time I hate them because half the time I discover a solution myself 2 seconds after I upload a thread………. The other half is great having other minds to bounce ideas off of. Still other times it is always humbling to be reminded how stupid you can be. Twenty years ago I would have just ground the gun up. Retired now, so I no longer have the creeping need to complete the task NOW, because I had other things to do. Back to the thread.

MATERIAL
More than one person mentioned different types of material + flat and round as possibilities. With the limited space were the spring goes, flat is the only shape the will keep the spring in place and under tension.
Also, several people have mentioned different materials for the spring. I have purchased this specific tempered blue spring steel from a reputable dealer (Not cheap) to avoid the issues with unknown types of spring steel. So I don't see how that could be the issue, unless I am missing something.

90 DEGREE BENDS
I have to work by myself, so I guess I will machine a jig for the 90 degree bends. I thought about that early on, but like most proper ideas, sure seemed like a lot of work for one spring. I will sit and think about making a jig that can hold different size pieces of spring material, with an open area where the spring will bend so that heat can be applied and I can immediately make the bend with just 2 hands……. We shall see.
The odd part is that both billdeserthills & ZigZagZeke mentioned annealing the steel first. I have always done that, and it seemed to work. But, for some reason with this very-very thin spring steel it does not seem to anneal properly. I anneal, bend, and it snaps. Even doing the gentle rounded bend, not just the sharp 90 degree bend. Is there a different amount/length of heating required to anneal this thin a piece of steel? I really need some additional feedback on this part. Any ideas?
I understand P7M13's ideas, but I am not sure a kiln would even work. It is strange. The metal is so thin a .017" thickness, if I heat to red and immediately touch it with anything (like pliers), that area immediately goes from red to dull because of the heat sink occurring form the tool. I have tried to heat the tool also (To below red) so that it is not 'cold', but that does not seem to help. Why? Again, I have done this making other springs and never had this difficulty????

HEATING & QUENCHING
For the Heating a quenching step I think I will get a fire brick and set the spring on its side, on the edge of the brick. Then at temperature I can quickly just push the spring over the edge of the brick and into the waiting oil. I can see that should be sufficient.
A follow up question. Is there a different temperature needed for very-very small material, than for normal thicker springs? I only say this because I most often successfully create a normal sized spring on the first or second try. After 6 or 7 tries on this one, still no success.

I will move forward on these ideas and see what happens. Just not comfortable that the issues are solved yet…………….