Mikrometern

Mikrometern, known in English as the micrometer, is a precision instrument used to measure small linear dimensions with high accuracy. The most common type, the outside micrometer, measures external dimensions such as the thickness or diameter of parts, while inside micrometers measure internal diameters and depth micrometers measure recess depths.

Principle: Measurements are based on a calibrated screw with a known pitch. Rotation of the thimble moves the spindle toward or away from the anvil. The main scale on the sleeve provides whole millimeters; the circular thimble carries graduations (often hundredths of a millimeter or thousandths in higher-end models) that, together, yield the final reading. Many micrometers feature a ratchet stop to apply a consistent measuring force and a zero adjustment to tare the instrument.

Accuracy and ranges: Standard outside micrometers offer a least count of 0.01 mm (10 μm); higher-end devices provide 0.001 mm (1 μm). Common measuring ranges include 0–25 mm, 25–50 mm, and larger. Readings may be expressed in millimeters, or converted to inches on imperial micrometers. Digital micrometers display the measurement directly.

Calibration and use: Regular calibration with gauge blocks ensures accuracy; technique requires stable contact, avoiding deformation and parallax errors. They are widely used in machining, quality control, and laboratories to verify tolerances and wear.

Types and variants: Outside micrometers, inside micrometers (using measuring anvils and a spindle with extension rods), depth micrometers, and specialized formats such as digital and dial-indicator micrometers.