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Re: Screw Factor of Safety?

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On Aug 30, 2004, at 4:37 PM, Jim Wilson wrote:

Most catalog fasteners (i.e. self-drilling screws, epansion anchors, etc.) have a factor of safety of 4(or higher) for design.  Is there a different factor of safety when considered during field testing?
I wouldn't dream of making a generalization like this. If someone is asking you to substitute something on this basis, he'd have to prove to me, or pay me to prove it for him, that the substitute item is suitable for the design loading, with the customary margin (eg a margin of two against ultimate strength for a bolt for like items under the specified service. When a guy with an ax to grind waltzes into my life announcing that something has a safety factor of du-wah, he better be ready to show me the numbers.

Christopher Wright P.E.   |"They couldn't hit an elephant at
chrisw(--nospam--at)      | this distance" (last words of Gen.
.............................................| John Sedgwick, Spotsylvania 1864)

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