Which part is NOT a component of a micrometer caliper?

A micrometer caliper is a precise instrument used for measurement, particularly for small dimensions. The main components of a micrometer include the thimble, spindle, and anvil.

The thimble is the rotating part that moves the spindle and allows users to take measurements by specifying how much it has been turned. The spindle is the part of the micrometer that moves in and out and comes into contact with the object being measured. The anvil serves as the fixed reference point against which measurements are taken.

The term "head screw" is not recognized as a standard component of a micrometer caliper. Instead, the micrometer typically has a frame or body that houses the other components and provides support. Therefore, identifying a head screw as a component of a micrometer caliper is inaccurate, making it the correct choice for what is not part of this measuring instrument. Understanding the function and relationship of the thimble, spindle, and anvil helps clarify their importance in the overall functionality of a micrometer caliper.