The 1 7/8-8 NS HSG H6 1204R46W USA BOTTOM TAP is a high-speed steel (HSG/HSS) ground-thread industrial hand tap designed to cut a 1-7/8" nominal diameter thread with 8 threads per inch (TPI). This specific configuration is typically used for heavy-duty industrial machinery, oilfield components, or large mechanical assemblies. 
Technical Specification Breakdown
  • 1 7/8-8: Indicates a 1-7/8" major diameter with an 8 pitch (8 TPI) configuration.]
  • NS: Stands for National Special, meaning the thread pitch and diameter combination falls outside the standard UNC/UNF series but adheres to Unified thread forms.
  • HSG: Signifies High-Speed Ground (often interchangeable with HSS), meaning the flutes and thread form are precision-ground out of high-speed steel for long tool life and accuracy. 
  • H6: Represents the Pitch Diameter Limit. An H6 limit means the tap's pitch diameter is oversized by .0030" to .0035" over the basic pitch diameter to account for material shrinkage, heavy platings, or precise class of fit requirements. 
  • 1204R46W / USA: This alphanumeric sequence is a manufacturer-specific tool or catalog number (commonly associated with premium domestic brands like Regal Cutting Tools). It specifies the exact metallurgy, flute structure, and geometry. 
  • BOTTOM TAP: A bottoming style chamfer featuring only 1 to 1.5 chamfered threads at the tip. It is engineered to cut threads cleanly down to the very bottom of blind holes.