What unit is diameter measured in for screws and bolts?

The measurement of diameter for screws and bolts is commonly expressed in inches or fractions of inches, particularly in the United States, where the imperial system is prevalent. Using sixteenths of an inch provides a very precise and detailed way to indicate the diameter of small fasteners. For instance, a screw might have a diameter specified as 1/4 inch, which is equivalent to 4 sixteenths of an inch. This method of measurement is especially useful in industries where precise dimensions are crucial for the functionality and compatibility of components.

While millimeters and centimeters are used in some contexts, particularly in metric systems, and inches are certainly a common unit, specifying diameters in sixteenths of an inch allows for more precise communication of size. It is important to note that in aviation and many engineering fields, exact measurements can make a significant difference in joinery and fitment.