[TheForge] rigid vs. springy steel

[Peter Fels & Phoebe Palmer]

Jerry's temper recommendation is a bit less conservative than mine, but makes sense.
The question is the failure mode...Do you want it to hold up with little wear till you finally abuse it and it snaps abruptly,
or would you were rather it was tougher, softer, and fail by bending?

On Jul 25, 2013, at 12:12 PM, Jerry Frost wrote:

You're on the right track Bruce, a little thicker and more tightly wound AND don't put a spring temper on it, only draw it back to medium to dark straw and you'll be good to go. Oh yeah, spring steel is a good choice as it's more forgiving in the heat treat so little differences in temperature don't have major effects.

I guess I'll *never *learn and keep on replying before reading the whole post. <sigh>

You're wanting to make a speed bar,  great tools, I have a few though I've never made one. I'd forge it down from spring stock and temper it to medium straw. springs are typically drawn back (tempered) well into the blue. You'll want to make a couple test pieces (coupons) to get the temper right, they WILL be struck with hammers so do a few tests.

A good alternate stock is found in tire irons, lug wrenches or (big surprise!) pry bars, yard/garage sale stuff. Again, make some test coupons as a departure point I'd draw the temper down to the straw and adjust from there depending on the test coupons.

Jer


On 7/25/2013 1:06 AM, Bruce . wrote:
> Here's a question you metal munchers might be able to field:
> 
> I have had a few applications in which I need thin but rigid steel.
> What steel is best?
> 
> Consider for example a corkscrew -- it's a helix that holds its shape,
> it's rigid.  But a spring with a comparable shape is flexible.  What's
> the difference?  I suspect that it's simply the relative dimensions --
> a spring is relatively thinner wire wrapped on a relatively larger
> mandrel, and vise-verse the corkscrew.
> 
> But is that all there is too it, or is there a metallurgical difference as well?
> 
> Although I've contemplated making corkscrews, the immediate
> application is a prybar for roofing and siding nails and similar
> stuff.  It would be flat, like these:
> http://www.homedepot.com/p/Dasco-Pro-Pry-Bar-Set-3-Piece-91/202585548#.UfDoym1cWgw
> but of thinner steel.  (If I can't make it thinner, I'll just use a
> commercial one.)
> 
> I'd like it as thin as possible for a number of reasons, but I don't
> want more than minimal flex to the thing.  So I'm wondering what steel
> to use.
> 
> I have, BTW, considered using thin steel and putting longitudinal
> bends ("ribs" or "nerves" or "corrugations" -- whatever you want to
> call them -- as are used in larger HVAC ducts to prevent oilcanning of
> the large flats) in it, but this partially defeats the purpose, as the
> result would effectively be thicker -- so why not use thicker metal
> and be done with it?
> 
> This is not any sort of critical problem, but I've had similar
> problems before and left them unaddressed.  This time I thought I'd
> ask....
> 

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