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Re: Stripping Treads

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I'd probably spend a few minutes with a thread gauge & mic to decide something about end effects (or just discount the first thread or two). With the tabulated areas I sent him the "calculatiions" would take about a minute. Or you could fire-up a test program :o)
Chuck Utzman,P.E.

Jordan Truesdell, PE wrote:

This brings up a reasonable question: Is it worth running five or six pull tests on a similar condition in the lab? You certainly could spend a good amount of dollars in time running down a theoretical solution, and still not being confident that the math matches the real world.

Jordan



Christopher Wright wrote:


On Sep 29, 2006, at 2:56 PM, Rich Lewis wrote:

m looking for the design equation for stripping threads.

Machinery's Handbook has all you need, and a good deal more. One thing I would say--the basic equation assumes a lot of things that aren't likely to be true for only two or three engaged threads. The first couple of threads that are engaged are likely to be imperfect and won't allow the ultimate load to be distributed evenly. If you have cycclic loading, you need to consider the stress concentration factor at the root of the threads. I don't think much of using the relationship for stripping with only a few threads engaged becasue it doesn't account for end effects -- no need with plenty of engagement since the end effects don't extend over much of the fastener length. With minimal engagement, it's all end effect, so most of the premises of the stripping equation are out there hanging in the grey area that no one much worries about. .
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw/



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