A micrometer is a measuring tool used to precisely measure lengths on small scales. In principle, spiral micrometers can be divided into mechanical micrometers and electronic micrometers. The mechanical micrometer is made according to the principle of spiral magnification.

#### What is a Micrometer?

A spiral micrometer (Micrometer) is a more precise tool for measuring length than a vernier caliper. Using it to measure length can be accurate to 0.01mm, and the measuring range is several centimeters. It is used to measure the thickness of aluminum foil or similar aluminum foil objects and other objects that need accurate measurement and output data.

The screw micrometer is a more precise tool for measuring length than the vernier caliper. It can measure the length accurately to 0.01mm, and the measuring range is several centimeters. The fixed scale of the small anvil of the screw micrometer is fixed on the frame, the knob, the fine-tuning knob, and the movable scale, and the micrometer screw are connected and are sleeved on the fixed scale through precision threads.

**Working principle:**
The screw micrometer is made according to the principle of screw amplification. The screw rotates once in the nut and the screw advances or retreats along the direction of the rotation axis by a distance of one pitch. Therefore, the small distance moved along the axis can be expressed by the reading on the circumference. The pitch of the precision thread of the screw micrometer is 0.5mm, and the movable scale has 50 equal division scales. The movable scale rotates once, and the micrometer screw can advance or retreat 0.5mm, so rotating each small division is equivalent to the micrometer screw Forward or backward this 0.5/50=0.01mm. It can be seen that each small division of the movable scale represents 0.01mm, so the screw micrometer can be accurate to 0.01mm. Since one more digit can be estimated, the thousandths of millimeters can be read. When measuring, when the small anvil and the micrometer screw are close together, if the zero point of the movable scale coincides with the zero point of the fixed scale, unscrew the micrometer screw. And make the surface of the small anvil and the micrometer screw just touch the two ends of the length to be measured, then the distance that the micrometer screw moves to the right are the measured length. The whole millimeter of this distance is read from the fixed scale, and the fractional part is read from the movable scale.

- The precision of the scale: Its smallest scale, usually 0.5 mm.
- The precision of the spiral micrometer: It is obtained from the cooperation of the auxiliary scale and the scale, and is the minimum scale of the auxiliary scale.

**Basic types of micrometers:**
- Outside Diameter Micrometers: Commonly used to measure wires, spheres, shafts, and blocks.
- Inner diameter micrometer: Used to measure the diameter of the hole.
- Depth micrometer: Used to measure the depth of the groove.

**Measurement method:**
- From the position of the front edge of the movable sleeve at the position of the fixed sleeve, read the number of complete turns.
- From the number of divisions on the movable sleeve opposite the horizontal line on the fixed sleeve, read the decimals less than one circle, and the addition of the two is the measured value.

#### What is the Unit of Measurement for the Micrometer?

A micrometer is a more precise tool for measuring length than a vernier caliper. It can be used to measure length to an accuracy of 0.01mm, and the measurement range is several centimeters. A part of the thread is processed into a thread with a pitch of 0.5mm. When it rotates in the screw sleeve of the fixed sleeve B, it will advance or retreat. The movable sleeve C and the screw are integrated, and its periphery is divided into 50 divisions. The number of full revolutions of the screw is measured by the engraved lines at intervals of 0.5mm on the fixed sleeve. And the part that is less than one turn is measured by the engraved lines around the movable sleeve. The final measurement result needs to be estimated to one decimal place.

#### Various Micrometers and Their Corresponding Functions:

- Vernier reading outer diameter micrometer is used for ordinary outer diameter measurement.
- Small head outer diameter micrometer is suitable for measuring precision parts of clocks and watches.
- The pointed outer diameter micrometer is characterized in that the two measuring surfaces are 45° cone-shaped pointed heads. It is suitable for measuring small grooves, such as the groove diameter of drill bits, vertical end mills, taps with even grooves, and the diameter of the tooth root circle of watch gears.
- The wall thickness micrometer is characterized by a spherical measuring surface and a flat side measuring surface and a specially shaped ruler frame, which is suitable for measuring the outer diameter micrometer of the pipe wall thickness.
- Plate thickness micrometer the plate thickness micrometer refers to a ruler frame with a spherical side measuring surface and two flat sides and a special shape, which is suitable for measuring the thickness of the plate.
- Thin slice micrometer measures the diameter of the groove, which can reduce the measurement error by 5% each time.
- Disc micrometer measure the span length of the spur and helical gears.
- V felt micrometer odd-numbered taps, reamer outer diameter measurement.
- Spline micrometer, also known as fancy micrometer, gear groove diameter measurement.
- Caliper type inner diameter micrometer small diameter narrow groove width measurement.

#### What is the Difference Between Micrometers and Calipers?

The micrometer is also called the spiral micrometer, and the accuracy is estimated to be 0.01mm to 0.001mm.

The vernier calipers are divided into three types: 10 divisions, 20 divisions, and 50 divisions, and the accuracy is 0,1mm, 0.05mm, and 0.05mm respectively.

#### Matters Needing Attention When Using a Spiral Micrometer:

- When measuring, stop using the knob when the micrometer screw is approaching the object to be measured, and use the fine-tuning knob instead to avoid excessive pressure, which can not only make the measurement result accurate, but also protect the screw micrometer.
- When reading, pay attention to whether the engraved line indicating half a millimeter on the fixed scale has been exposed.
- When reading, there is an estimated number in the thousandth place, which cannot be thrown away casually. Even if the zero point of the fixed scale is just aligned with a certain scale line of the movable scale, the thousandth place should be read as 0.
- When the small anvil and the micrometer screw are close together, the zero point of the movable scale does not coincide with the zero point of the fixed scale, and there will be a zero error, which should be corrected, that is, the value of the zero error should be removed from the reading of the final length measurement.