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?
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).
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.
