CPC Main Group B23F 9/00 Making gears having teeth curved in their longitudinal direction 4 direct subcodes Child Classifications Navigate with arrow keys, Enter to open B23F 9/003 B23F 9/02 by grinding B23F 9/04 by planing or slotting with reciprocating cutting tools B23F 9/08 by milling, e.g. with helicoidal hob