Upon a deviation of the bore diameter being measured from the required value, sensitive contact 1 is displaced and it actuates lever 2 which turns about fixed axis A. Through rods 3 and 4, the motion of lever 2 is transmitted to measuring spindle 5 of dial indicator 6. Spring 7 maintains constant contact between members 1, 2 , 3 , 4 and 5. Spring 8 holds locating fork 9 against the bore. Bore diameters are checked by comparison with the hole of standard ring 10.
$472$SL,M$