Need to duplicate an old flat spring

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of.
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The set consists of several different thicknesses. Are you telling us that the spring in your device is only 0.005" thick, yet FAR stronger than a steel feeler gauge of the same 0.005" thick?
Llyod

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Mike, how thick is the original spring? What the guys are saying is you need the same thickness feeler guage. Half as thick is 1/8 as "stiff", so .005" is 1/8 as strong as .010 - and i suspect your spring as closer to .020 or 025"

On 8/5/2013 8:42 PM, BQ340 wrote:
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Of course it will distort - that's how it works - by flexing. Unless by "distort" do you mean "yield", with a permanent distortion. If so, I don't think so - feeler guages are pretty hard & the video doesn't show that much deflection in the springs. Try bending a feeler guage by hand - about the same radius as the Omnigraph spring while running. Does it yield? If not, keep trying smaller radii until it does yield. I'll bet that the radius that it does yield at is much smaller than will ever happen in the Omnigraph. In which case, you're set to go.
Bob

On 8/6/2013 8:50 AM, Bob Engelhardt wrote:
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Yes, it kinks permanently, I am bad with my terminology!
The problem seems to be that it doesn't bend evenly along it's length in use, the 3 attaching screws have square plates under the heads to clamp the spring & weights -they must focus the force and leave a slight crease in the shim stock after a couple test runs. It almost works but I'm not happy with the results.
I am trying to keep this original as possible, not just hack it up with any old spring that will "work".
MikeB

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So... you use a spring of equal hardness to the original, and equal thickness, and equal width.
Just because the feeler gauge stock isn't hard enough is not a limitation. Harden and temper it.
Lloyd

On Tue, 06 Aug 2013 16:39:54 -0500, "Lloyd E. Sponenburgh"
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If he hasn't done that before, trying to get it right with such a thin piece is not likely to be successful.
Quenching a thin blade evenly isn't usually accomlished by dunking it in water or oil. You'll preferentially quench one side, resulting in a weak and, probably, a curved piece. Swishing it around does NOT accomplish it, if we're talking about something thinner than 0.030" or so.
I have a nozzle made as a coil of bendable copper tubing, with many spray holes pointing inward, that screws to my laundry-tub faucet. I made that after a lot of wrecked pieces.

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Not if you PLUNGE it vertically. Besides, he can layer material to equalize the quenching.
C'mon... this isn't rocket science, it's craftsmanship. Artisans have been doing it successfully by hand for three centuries.
Lloyd

On Tue, 06 Aug 2013 16:58:50 -0500, "Lloyd E. Sponenburgh"
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Good luck. I haven't been successful doing that, except once or twice by pure luck, and I've heard from experienced heat-treating people, and knife people, who also say not to do it.
Maybe your eye/hand coordination is a lot better than mine d8-)
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This is a very thin blade. They're very hard to quench right. My experience is mostly with hacksaw bladers, carbon steel, which I use for a lot of things.

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The action of a fly-weight governor is controlled by two things. the weight of the fly-weights and the strength of the springs. Altering either alters the critical RPM.
So, you can make a couple of new springs and try them. If the speed falls in the right area you say there is adjustment. If not then make two more springs, either stronger of weaker as the case may be.
It's not rocket science and you can cut and drill most spring material with common tools. It is a guess but I'd think that once you obtain some spring stock, say a spring from a steel tape, and collected the tools you could probably make 10 or 15 pairs in an hour, or maybe more.

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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.
jsw

OK make it simple enough for me. I'd order spring steel from Mcmaster carr 1074/1075 http://www.mcmaster.com/#standard-spring-steel-sheets/=nxj9lp
make the part the right dimension.
Now, what hardening procedure gives the optimum results?
Karl

On 8/5/2013 7:11 AM, Jim Wilkins wrote:
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I'm listening, just not understanding!
So you are saying I can't change the properties of a spring, that I must find the same material as the original if I want the new spring to be the same dimensions as the old one?
MikeB

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must
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Almost correct: You can change the properties by hardening/tempering... just not the spring force. It remains the same (nearly) for any given alloy, regardless of the hardness
The primary property you change by altering the hardness is the yield force, NOT the spring force.
You also can affect (positively) the durability of the spring by increasing the yield point IF the deflection is such that it comes close to the yield point when not hardened.
Someone recommended feeler gauges for stock. Also consider the rewind springs in cheap tape measures (don't use an old, discarded one, as it might already be severely fatigued).
Lloyd

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You don't have to match the original grade of steel, they all have the same elastic properties, or Young's Modulus, below the yield point.
Can you adjust the weight?
jsw

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Lloyd answered that clearly -- the spring rate will be almost exactly the same, no matter what grade steel you use (except stainless) and no matter how hard or soft it is.
What varies is the yield point (look it up) and, consequently, the fatigue life.
Maybe we can simplify this for you: How much, in inches or millimeters, does that spring deflect at the ends, when it's in use?
Be patient; you'll get it. By now you know that you started with some very common misconceptions. I've even known experienced machinists who didn't believe it when it was explained to them. So you're not alone.
But we'll enlighten you. d8-)

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Ok, given your application, I'd suggest that you take the advice of another poster and buy some spring stock from Brownell's. The one-off flat-spring business is something that gunsmiths and their suppliers are very good at. It probably is the easiest way for you to arrive at a solution.
I haven't looked at a Brownell's catalog for close to 20 years, but for many things, they're the source. They know what they're selling.

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Its possible to make one in less time than finding one.

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You can harden it. Tempering it reduces the hardness.
"Tempering" is the process of taking full-hard metal and reducing the hardness in order to increase the durability and flexibility.
So... quench-harden it to full-hard, then temper it down.
Lloyd

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Generally..they arent supposed to snap. When springs get old..they get brittle and break. Is it supposed to Snap?

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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....