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clamp load - bolt vs. stud and nut

clamp load - bolt vs. stud and nut

clamp load - bolt vs. stud and nut

(OP)
Does anyone out there know if there is any difference in the clamp load generated in a joint using a stud and nut, versus the same joint using a capscrew?

RE: clamp load - bolt vs. stud and nut

A stud, being fully threaded, will be more flexible in extension than the same nominal size, partially-threaded bolt or cap screw (the unthreaded portion of a bolt has a slightly higher stress area, thus is slightly stiffer than the threaded portion).  Thus, a stud may produce a slightly lower clamp load for the same extension as a bolt.  For the same applied torque, there is no difference, except:

Depending on the type of cap screw and type of nut, differences in the head size (bearing area or contact area) can/may affect the relationship of torque vs. preload.

Both effects are likely pretty small (less than the error inherent in estimating preload from torque alone).

RE: clamp load - bolt vs. stud and nut


Assuming that the the desired bolt stress is identical in both cases, it's a bit of a wash: The Effective Length of a joint contained by a stud and two nuts is equal to the the Grip Length plus  one-half of each nut height. Thus, this usually becomes the Grip Length plus one Nominal Diameter. However, when working with a bolt and one nut, the Effective Length is equal to the Grip Length plus one-half the nut height plus one-third the height of the bolt head. Therefore, since the former has a longer Effective Length, it has more clamping effect.

Ciao,

HevïGuy
www.heviitech.com

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