One measuring device for round outside diameters of for example shafts, bolts or pipes is called outside micrometer or quick micrometer.
The micrometer and the bracket form a fixed unit. The measuring ranges in trade and industry are mostly between 0 and 500 mm. micrometers.
There are micrometers that have plates with a larger diameter than the screw shaft to measure gear
toothing. These are called plate or flank micrometers.
Radial grooves are measured with outside micrometers with flat and leveled measuring surfaces. Furthermore there are inserts with tapered measuring surfaces.
External threads of screws, threaded bolts, etc. are measured with outer micrometers, which have changing inserts to adapt to the pitch and type of thread.