6-32 STI-28 thread 1

[ewh]

Is anyone familiar with a "STI" thread callout? I have a drawing specifying it, and it also specifies a pilot diameter of .147 (for a 6-32). Could this be a threaded insert prep callout? The hole is in aluminum.

 

[BillPSU]

This is a heli-coil application.

 

[ewh]

Thanks BillPSU. I thought it must be something like that, but I didn't have any literature handy. I am accustomed to calling out heli-coil holes as "PER NASM33537" and the STI threw me.