a screw with a fine thread of definite pitch, such as that of a micrometer gauge
micrometer screw in American English
(maɪˈkrɑmətər)
a finely threaded screw of definite pitch, with a head graduated to show how much the screw has been moved in or out: used in micrometers, etc. togive fine measurements, as of thickness, sometimes to .0001 of an inch