Stretch Control 3
There are several factors, which complicate this method:
When we think of the bolt as a complex spring, the unthreaded body of the bolt is a relatively stiff spring and the threaded portion of the bolt can be considered to be a less stiff spring. When we load a bolt, the
threaded portion of the bolt will tend to stretch more than the unthreaded shank of the bolt. Threads within the nut, or within a tapped hole, will also stretch less. The amount of engaged and unengaged thread
stretch is directly affected by the fastener diameter. Calculations must be made using exact lengths of both the unthreaded portion of the bolt and the remaining length of the unengaged threaded portion of the bolt
and also the diameter of the bolt.
