Steel Purlins

A fastener penetration of three threads through the steel member is sufficient for the fastener to meet its full design capacity.  Pull-out failure of screws must be checked when assessing a profile's load/span capacity.

The pull-out values of screws into light gauge steel battens or purlins varies greatly with thread design, pitch, and drill point shape. When fastening into light gauge steel, the pull-out values of the specified screw must be considered, and the installation must be completed with that type, gauge, and brand of screw. In light gauge steel under 1mm in thickness, it is also important to avoid stripping out the formed screw thread