STI-HSS Taps

Thread Kits Company offers a complete line of high speed steel “STI” taps, available in “Plug” style – used for starting or tapping a through hole, and “Bottom” style – used for tapping to the bottom of a hole or blind holes.
STI (Screw Thread Insert) taps are an oversized tap used when installing a wire insert. When the damaged hole is tapped by an STI tap, and a Perma-Coil insert is installed, the hole goes back to the original dimension allowing the original fastener to be used.
Because Perma-Coil inserts conform to the tapped hole, the class of fit of the final assembly is a function of the tapped hole. Perma-Coil STI taps are available in Inch Series in Class 2B and 3B fit – 3B having a slightly tighter tolerance, and Metric Series in Class 4H and 4H5H fit – with 4H5H having a slightly tighter tolerance.