hexagonal plug / threaded / locking
KATO CoilThread STI (Screw Thread Insert) Thread Plug Gages are designed to check the accuracy of the internal thread of an STI tapped hole. Gaging the tapped hole prior to installation of the insert is critical to ensure the accuracy of the finished thread. If the tapped hole gauges correctly, the finished thread will also be accurate once the insert is properly installed and seated.
It is not necessary to gage the installed insert. Gaging of the tapped thread is specified because a standard gage may not freely enter an installed insert. The insert will seat itself once a bolt or screw is installed and tightened (Ref. NASM33537). In fact, it is not possible to gage a locking type insert because of the locking coil.