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Re: Stripping Treads

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Gee, this is going to show my age.  I found a 10 pg. article from Product Engineering dated Nov. 27, 1961 that look like it will do the job for you.  Send me your FAX # & I'll sent you a copy.
Chuck

Rich Lewis wrote:

Chuck,

 

Yes, please do, since I can’t find many other resources.

 

Rich

 

 


From: chuck utzman [mailto:chuckuc(--nospam--at)pacbell.net]
Sent: Friday, September 29, 2006 3:34 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Stripping Treads

 

I could take a look in my Northrop Design Manual circa 1968  :o) is that prior enough?
Chuck Utzman, P.E.

Rich Lewis wrote:

I’m looking for the design equation for stripping threads.  I have anchor bolts in tension and the bolt doesn’t extend through the nut.  Now I have to sharpen a pencil and see if the design tensile force is less than what would strip what is left of the threads on the bolt.  If not then the contractor will need to weld an extension onto the bolts.

 

I’m having a difficult time finding design literature on this.  AISC doesn’t cover bolts.  Logic tells me it is the area of shear of the pitch diameter of the threads.  Since the pitch diameter occurs midway between the peaks and valleys, it would be ½ the perimeter area of the threaded section put in shear by the tension force on the nut/bolt.  I found a reference for a bolt guide in one of Harold S old posts to a 1998 NASA RP-1228 “Fastener Design Manual”.  In this report they recommend using 1/3 the perimeter area of the pitch diameter to account for loose fit of the nut and bolt.  It makes sense to me.  The equation is P=(PI*DIA*Fs*L)/3 where DIA is the pitch diameter.  It is written for yield strength and ultimate tensile strength.  I was going to input 0.6*Fy and 0.5*Fu to come up with allowable loads.

 

I’ve been searching other books and haven’t found any reference to analysis or design recommendations for stripping forces on a thread.  Surely there had to be some recommendations prior to the 1998 NASA report.  Can anyone give me other references to analysis and design of bolt thread stripping?

 

Thanks.

 

Rich