Measurement of small lengths with great accuracy.
The most important piece of the instrument is a screw of fine thread, located inside a metallic structure equipped with two stops, one fixed and another mobile. The latter moves when the drum is rotated. In addition, it has a horizontal (fixed) scale divided into two parts and a vertical scale (mobile, which rotates when the drum rotates).
Once this is done, the only step that remains is to observe the scales, taking into account that the upper horizontal indicates the millimeters, the lower horizontal indicates the average millimeters and the vertical one hundredths of a millimeter.
The micrometer screw was invented in 1640 by William Gascoigne.
In 1829, Henry Maudslay built a bench micrometer that presented a scale divided into tenths of an inch and a drum, attached to the screw, divided into hundredths and thousandths of an inch.
In 1890, the American entrepreneur and inventor Laroy Sunderland Starrett patented a micrometer very similar to the current one.