The optional C axis was developed for job shop users where they may see many different pressure angles; as well as many different pitches. Without the C axis you need a diamond dressing wheel for each pressure angle you want to dress within a given DP range. With the C axis you can cover a +/-2.5 degree range from the pressure angle of the dressing wheel. So with two dressing wheels you can cover the range from 15 - 25 degrees.