1.OD under sized due over pressure in tail stock,as the pressure was given was 2BAR's.|2.The min. pressure in the new machine's is 1BAR, but in the old machines it was 0.5BAR.  |3.Due to over pressure the part had bent,the operator was not having the knowledge about the pressure that had to be given to the tail stock. |4.After the part had bent the OD operation was performed and the OD was achieved,but after removing the part from the chuck and measured it again the OD was undersized by 0.015mm. |Why 5: Usually the tail stock pressure maintained was 1.5bar but in the new machine the pressure was varying 1bar, 2bar, 3bar,etc. therefore the operator got confused and provided 2bar pressure to avoid rotation of the part during machining.