At the time of adjusting underlay iron of the bearing according to conventional calculation method

real centre of the rotor isn't varying in conformity with the estimated value

there is a certain error existing. It is often necessary only to adjust the thickness of underlay iron for many times the requirement can be achieved. Through calculation analysis

the causes and regularity leading to error occurence have been found

and a method of calculating correct adjustment quantity of the underlay iron being put forward

enhancing the efficiency of repair work.