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Re: cut threads vs rolled threads

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>what it the difference between having cut threads or rolled threads?  Is 
>there any difference in strength or performance?
It depends on the bolting specification--A-325 states that threads that 
threads may be rolled or cut. A-574 (high strength cap screws) requires 
rolled threads for screws smaller than 5/8-11 and up to 4 inches long; 
anything over those limits can be machined or rolled. There are no 
distinctions made between rolled or cut threads as regards strength.

I infer that it doesn't matter much if the application or the material is 
not overly fatigue critical. A-574 bolts in the smaller sizes have high 
mechanical properties (180 ksi UTS and 140 ksi YS for sizes less than 1/2 
inch) and are probably a lot less notch tolerant than lower strength 
grades--the requirement for rolled threads probably addresses this. The 
NASA Fastener Design Manual states that rolled threads leave compressive 
residual stress at the thread roots with helps fatigue resistance. I 
daresay anchor rods don't carry much in the way of cyclic loading, absent 
ongoing uplift forces.

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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