 Face Grooving Dia. φD Face grooving diameter (φD) is the suitable value for the initial grooving on the unprocessed workpiece (Ref. to Fig.1). Then, you can widen it up to the center towards the W inside (excluding the models listed in the right table) ID MIN ID MAX and towards the outside according to machine limits. T Fig.1  Limit of Turning toward Center Turning towards the Center causes the toolholder to interfere with the groove wall depending on the initial cut's diameter. φD 25 26 27 28 G and over Description φd (mm) Id KGDF& 2020X25-3AS Boss) 2525X25-3AS 4 2 0 KGDF& 2020X25-4AS 6 3 0 (No remaining Grooving ID 2525X25-4AS Interference KGDF& 2020X25-5AS 7 4 1 2525X25-5AS Remaining Boss Dia. φd KGDF& 2020X25-6AS 2525X25-6AS 9 4 1 0 e.g.) KGDFR2020X25-3AS with φ25 as first cut towards the center, it will cause a rubbing with the toolholder cartridge if φd is 4.0mm. G77