Step Drills : 
 
  
  4/5/6/7/8/9/10/11/12 MM
  
  4/6/8/10/12/14/16/18/20 MM
  
  6/9/11/13/15/17/19/21/24/27/30/33 MM
  
  6/9/12/15/18/21/24/27/30/32/34/36/38/40/42 MM