STI Screw Thread Insert Gages (Working Thread Plug)
Working thread plug gages are used to ensure the threaded hole complies to specification, normally either a 2B or 3B classification. In the case of Screw Thread Insert (STI) gages, the thread designation refers to the insert thread so the size of the gage for the tapped hole is larger than the nominal size.
- Working thread plug and ring gages are furnished with Standard class “X” industry tolerance
- For rings with class “W” tolerance pitch diameters, set plugs must be ordered or provided
- Set plugs are truncated and have class “W” tolerances on lead and class “X” tolerances on the pitch diameter
STI Screw Thread Insert Gages are used to measure the pitch or lead of threaded holes prior to insertion of screw thread inserts.