Micrometer-Definition, Parts, Working, And Applications

A micrometer is an instrument used for making precise linear measurements of dimensions such as diameter, thickness, and lengths of solid bodies.

What is Micrometer?

A micrometer is a precision instrument used to measure extremely small distances, such as the diameter of a wire or the thickness of a sheet of metal. The micrometer consists of a spindle, anvil and thimble, which interact to provide an accurate and repeatable measure of the distance between them.

The spindle is adjusted through a screw thread, while the anvil and thimble move in unison due to the action of the screw thread. The micrometer is capable of precise measurements down to thousandths of an inch.

The heart of the micrometer is the spindle, usually made from hardened steel. The spindle is attached to the thimble and a nut, which moves the spindle axially along the barrel. The thimble is marked with linear measuring units, usually in millimeters.

The barrel also has a scale that is marked with linear measuring units. When the thimble is turned, the spindle is moved axially along the barrel, and the measurement reading is taken on the barrel.

The precision of a micrometer is usually expressed in terms of the number of divisions on the thimble and barrel. The higher the number of divisions, the more precise the measurement. The accuracy of the measurement is also affected by the condition of the anvil and spindle.

Micrometer Parts

These are important parts of micrometer.

Frame

The C-shaped body that keeps the anvil and barrel in continual contact. It is thick to prevent bending, expansion, and contraction, which would affect the measurement.

Because the frame is hefty, it has a large thermal mass, which prevents the holding hand/fingers from overheating. It is frequently coated with insulating plastic plates, which reduces heat transfer even further.

Anvil

The gleaming component toward which the spindle advances and against which the sample rests.

Screw

It is located inside the barrel and is called the micrometer’s heart.

Barrel

The stationary spherical component with a linear scale and, on sometimes, vernier markings. The scale on certain instruments is marked on a tight-fitting but moveable cylindrical sleeve that fits over the internal fixed barrel. This enables for zeroing by slightly adjusting the location of the sleeve.

Spindle

A gleaming cylindrical component that moves the thimble toward the anvil.

Working Principle of Micrometer

The operating principle of a micrometer is based on the principle of contact measurement. The object to be measured is placed between the anvil and the spindle. When the thimble is turned, the spindle is moved axially along the barrel, which in turn applies pressure to the object.

The amount of pressure applied is determined by the number of divisions on the thimble and barrel. The object is then measured by the amount of pressure applied. The accuracy of the measurement is affected by the condition of the anvil and spindle as well as the number of divisions on the thimble and barrel.

Application of micrometer

A micrometer is used to measure precise linear distances, such as the diameter, width, and length of an object. It is commonly used in mechanical engineering and machinist workshops to measure the external dimensions of an object such as a cylinder, screw thread, or block.

It can also be used to measure internal dimensions such as the inside diameter of a hole.

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