I need to duplicate an old flat spring but need to match the hardness or flex. The "spring" is just a small flat piece, 3/16" wide, 1-1/2" long and .005" thick.
It goes to a 1900's vintage device so the original would not have been anything exotic.
All I know is it really hard (brittle) -it will snap if you try to bend it in half.
I tried an old clock spring I had of the same thickness but that would bend, not snap so I need something harder.
Does anyone know if blue spring shim stock will bend or break? If it bends can I temper it more to get the hardness (flex) that I need?
Just one point: The hardness has nothing to do with the spring rate (the "flex") It only has to do with how far you can bend it before it either bends or breaks (the first if too soft; the latter if too hard).
There is a widespread misconception that hardness affects spring rates. It doesn't.
Sure. Is this a spring that has to be sprung (flexed) a lot? Often?
The less your spring bends, the softer it can be without taking a permanent set. But if it bends at a high frequency, that will reduce the degree to which it can be bent.
Is this an important spring for you? If so, let's identify the correct terms so you won't be confused when looking something up.
The spring rate for any given material is called the Young's modulus of the material. It's the same for nearly all types of steel, except for stainless, which has a slightly lower rate. It's also true for all degrees of hardness.
The degree to which it can be bent before taking a permanent bend is called its yield strength. For steel, harder steel has higher yield strength. But beyond a moderate point, it also can be more brittle. It will also *appear* to be more brittle, because it might break before it takes a permant bend.
Yes, this spring is one used in pairs as a speed regulator for an early telegraph device that I am fixing/restoring.
The flat spring strip is attached on both ends with a small weight in the middle. They fly out & raise a brass disk against a brake to regulate the speed, so it must be the same as the original to maintain the proper speed. (similar to a flyball governor on a hit & miss engine)
I can measure the deflection of the one unbroken spring under a given weight I guess, then experiment with different tempering temps to get as close as I can.
Heat treatability is dependent on carbon content. You have a piece you can spark test? Just barely touch it on a grinding wheel to check the spark display and find stock to match it... Then do the quench and temper treatment. Blue temper should get you close to spring action. You may have to do several....
flex. The "spring" is just a small flat piece, 3/16" wide, 1-1/2" long and .005" thick. It goes to a 1900's vintage device so the original would not h ave been anything exotic. All I know is it really hard (brittle) -it will s nap if you try to bend it in half. I tried an old clock spring I had of the same thickness but that would bend, not snap so I need something harder. D oes anyone know if blue spring shim stock will bend or break? If it bends c an I temper it more to get the hardness (flex) that I need? MikeB -- Email is valid
Flat spring stock is a standard item in the gun repairing trade, it's soft as furnished, you need to harden and temper it after sawing and filing to s hape. Cuts easily, I don't think there's one spring I've made that took mo re than a half-hour to get filed out. A knife can shave it, it's that soft . For that small an item, you use the clockmaker's trick with a steel plat e to temper, hold the plate over the flame with the spring-to-be on top. C oat the thing with soap to harden it to avoid scale. You might have to use water instead of oil to quench it for hardening to get a fast enough cooli ng rate. Polish after hardening, then temper to a blue color. You may hav e to do two or three before you get the hang of it, I usually make at least two for spares, just in case. Since you say they're in pairs, you've got a pattern to work from, should be easy. Polish out all nicks or your new sp ring will snap there.
If you've got to have some more formal instructions on old-timey spring mak ing, look up an old clockmaking book on archive.org. They used alcohol lam ps back in the day for that, so heat requirements aren't demanding.
See Brownell's or Dixie Gun Works for flat spring stock.
All steel bends the same, as long as it's not pushed so hard it takes a permanent bend. If one pound bends it one one-hundredth it will do the same nomatter what the temper ( or composition). This is a simplification, or course, there are minor differences, but on the order of a few percent.
To match what you have get exactly the same size. To find out how much it must take before bending you must bend the remaning one, so don't. Instead, make three new pieces exactly the same size, and try them. If they bend make three more, harder. Repeat as required.
How accurate does the speed regulation have to be?
You aren't listening. The temper / hardness does NOT affect the spring rate, only how far it will bend without damage. Make it too wide and grind it narrower to tune it.
If you don't believe us, clamp two long hardened drywall screws upright in a vise by the tips. Adjust the clamping depth so they both vibrate at the same pitch when plucked. Then anneal one to red heat with a torch. The pitch doesn't change, since the mass and Young's Modulus stay the same.
Push on them with your fingers. Both will deflect identically until the soft one yields.
DD fired this volley in news: snipped-for-privacy@nntp.aioe.org:
It looks to be a call-sign sender, maybe for portable hamfesting, or maybe a 'code' sender for a crypto pack, with canned messages. Kind of like our old 'Cack wheels' in 'Nam. You have a "sheet of the day" indicating a response numbers cross-reference. When you get a particular message that requires a particular response number, you look up the cross-referenced number of the day, which you then select on the stack of codes, and send back multiple times without any human errors.
The one he showed (not exactly like his)does appear to have a speed adjustment, by moving the friction disk up and down on the bottom sleeve of the centrifugal weights part. But it looks to be a very critical and difficult adjustment... no vernier is apparent.
Since automatic receiving equipment for certain CW codes was prevalent by the 1930s (ticker tape machines), it makes sense that the rate adjustment is pretty critical. The KSR and ASR teletypes followed shortly, and were in common use through the late 1970s.
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