# Newbie Question; Cold Rolled Steel bar

• posted
I have a shop making a digging tool which I resell. They use CRS 1".
My customers want to know what it would take to bend this bar if they pry
with it.
short of immobilizing one end of the bar in a horizontal position and adding
weights to the end of it, how can I describe it's "bendability"? *and*
where can I find that info?
I realize there are a lot of variables, like how long the bar is (48"), and
the range of temper and tensile strength it reached during it's manf., but
given all the above, what would it take to bend this bar?
Jim
• posted
I believe that any steel 1" bar will flex about the same amount. The question is how far can you bend the steel before it reaches its elastic limit. That parameter will vary.
I suggest you go check out "Machinery's Handbook" from your local library. There have been 26 editions, but any will do. Look in the index for the term "elastic limit" and follow the reference and start reading. Or, if you're more comfortable online, try googling for that term.
Grant
Jim wrote:
• posted
On Sun, 26 Oct 2003 21:12:45 GMT, "Jim" wrote something ......and in reply I say!:
And there you have the null question
Most steels bend about the same for a given set of impingements. But the difference is that some (spring steel for instance) will take a lot of bending and ...well...spring back.
You need to know the Yield Strength of the steel used, as it is actually sold.
It varies so enormously that you need to go back to the shop, find what steel they use, and where they get it from. Then you need to go to the suppliers, and get data on it as they supply to the shop. Then make sure that the shop does not heat-treat the steel enough to affect its properties.
_Then_ you can start to look at engineering programmes that tell you how much it can be forced before it permanently bends.
There is also the matter of simple fracture failure. Many steels will fracture before they reach their Yield Stength limit (or maybe it's _as_ they reach it, but it's a simple explosive "bend" )
Mind you, you could simply talk to the shop about it, and do a simple empirical test.
And be prepared to be unpleasantly surprised :
****************************************************************************************** Whenever you have to prove to yourself that you are not something, you probably are.
!!
• posted
Just a thought - have the shop building the units tell you what it will withstand so you don't create liability for yourself. If you say it will do "x" and it doesn't, then you will be the one holding the bag with no recourse. It's a lawyer's world these days.
--George
• posted
Tell them you are selling then a digging tool, but if they need a pry bar you can provide them with one. For an added cost of course.}:-)
Or if they want, you can up-grade the digging tool for prying for a small cost increase. Heck 33% cost increase sounds about right.
Red Rider
• posted
I assume you mean bend so it stays bent. As others have said, it depends on a lot of variables, but I found a quick look surprising, if I got my sums right.
Assuming a 1" dia bar 48" long constrained on one end with all force applied to the other end, a force of only 61.25 lb results in max stress of 30KPSI at the support. I think 25KPSI to 30KPSI is generallly used as a max safe stress for ordinary structural steel or CRS.
If you double that to 60KPSI I think it would be quite likely to bend. That would be a force of only 122.5 lbf.

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