Measurements provided by a micrometer are made up of a combination of values taken from the sleeve scale, the thimble scale and, on some micrometers, the vernier scale.
Micrometer sleeve scale
The sleeve scale of an imperial micrometer has a measuring range of 1 inch.
It is divided into increments of 0.025 inches and is numbered every 0.1 inches.
Micrometer thimble scale
The thimble scale has a measuring range of 0.025 inches (the smallest value that can be measured on the sleeve scale).
It is divided into 25 numbered increments, with each increment representing 0.001 inches (0.025 ÷ 25= 0.001).
Micrometer vernier scale
Some also have a vernier scale on the sleeve, which provides the user with readings of even greater accuracy (up to 0.0001 inches).
The vernier scale has a range of 0.001 inches and is graduated in 10 numbered increments, each of which represents 0.0001 inches.