GradeInsertExt. ToolholderInt. ToolholderThreadingGroovingEndmillDrilling ToolTechnical Reference Grade 1 1 Insert 2 External To o l h o l d e r 3 2 Internal To o l h o l d e r 4 Threading To o l 5 3 Parting, Grooving 6 4 Endmill 7 Drilling Tool 8 5 Technical Reference 9 6 7 8 9