Hello experts I have a machine Colchester cnc2000l...due to backlash issue I open my machine z axis balls crew assembly to rectify it...the wall was damage ...now I have to replaced the ball but can't understand which size of ball to be used..on the nut there is a mentioned about ball size (ball size is 1236) but not able to understand about 1236..how I determine the exact ball size...please need some advice..

Regards

Asif