To design the Anvil head for Deep Hole measurement, the following information is required:
ED - Smallest dia through which the given head has to pass
L - Length at which measurement is req. (Add extension if required)
The purpose of the Bush is to protect the Anvils when sliding through deep holes. For normal applications this bush is not required. When measuring deep holes user should ensure the alignment of Gauge axis and Bore axis. For measuring deep holes Spherical contact points are preferred because they allow certain amount of deviation in Gauge axis without affecting accuracy.