If the bore being measured deviates from the required diameter, the displacement of pin 1 is transmitted through ball 2, bearing against an inclined surface, and rod 3 to contact point 4 of a dial indicator. Spring 5 holds parts 1, 2 and 3 in contact with each other. Strip 6 with plates a is held against the walls of the bore by springs 7. The displacement of strip 6 is adjusted by screw 8. The motion of pin 1 (range of measurement) is adjusted by spring 9 which, in turn, is adjusted by screw 10. This enables the required initial deflection of the indicator hand to be obtained.
$2191$WL,M$