• 10 parts
  • Checked September 2026

Parts of a Micrometer

An outside micrometer side-on, from the C-shaped frame to the ratchet stop.

Parts of a Micrometer

Name Date

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1 2 3 4 5 6 7 8 9 10
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Write the name of each numbered part.Answer key

  1. Frame
  2. Anvil
  3. Spindle
  4. Thimble
  5. Sleeve (barrel)
  6. Ratchet stop
  7. Spindle lock
  8. Heat insulator
  9. Sleeve scale
  10. Thimble scale

Drawn for this site by script, 2026-09-26. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: another measuring tool, the combination square

All 10 parts on the diagram

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Start here: 6 main parts 6

  1. Frame The C-shaped body holding the anvil and spindle in line.
  2. Anvil The fixed face the object rests against.
  3. Spindle A precise screw that closes on the object from the other side.
  4. Thimble The part you turn to move the spindle.
  5. Sleeve (barrel) The fixed tube that carries the main scale.
  6. Ratchet stop Slips at a set force, so every reading uses the same pressure.

Frame, anvil and spindle 2

  1. Spindle lock Holds the spindle still while you read the measurement.
  2. Heat insulator A plastic plate that keeps hand heat from changing the reading.

Sleeve, thimble and scales 2

  1. Sleeve scale The main scale along the sleeve, read first.
  2. Thimble scale The scale round the thimble's edge, read against the sleeve's line.

How this list was compiled: Read 2026-09-26. (1) Wikipedia, Micrometer (device), https://en.wikipedia.org/wiki/Micrometer_(device) : frame, anvil, spindle (a very accurately machined screw), sleeve (barrel or stock, with the linear scale), lock nut (lock-ring or thimble lock, holds the spindle stationary), thimble, ratchet stop, insulating plastic plates on the frame, scale markings on the thimble and sleeve. (2) Mitutoyo, Quick Guide to Precision Measuring Instruments, https://www.mitutoyo.com/webfoo/wp-content/uploads/E11003-Quick-Guide.pdf and https://www2.mitutoyo.co.jp/eng/pdf/E4329_QuickGuide.pdf : frame, anvil, measuring faces, spindle, spindle clamp or spindle lock, sleeve (outer sleeve), sleeve scale, thimble, thimble scale, index (fiducial) line, ratchet stop, heat insulator, adjusting nut. Licence: own work

The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work

How it works

The parts of a micrometer, also called a micrometer screw gauge, on one outside micrometer side-on. Start with the 6 main parts, then the frame's fittings and the two scales.

Read the full guide

Holding the object

The object sits between the anvil, fixed on the frame, and the spindle, a precise screw that closes on it. Turn the thimble to move the spindle, and finish with the ratchet stop so the pressure is always the same. The spindle lock holds the reading.

Reading it

Read the sleeve scale first, along the fixed sleeve, then the thimble scale round the thimble's edge where it meets the line on the sleeve. The heat insulator on the frame keeps your hand's warmth from changing the size.

  • Hold the micrometer by the heat insulator, not the bare frame: warmth from your hand can change the reading.

Questions and answers

What are the main parts of a micrometer?

The frame, anvil, spindle, sleeve (or barrel), thimble and ratchet stop. Many also have a spindle lock and a heat insulator on the frame.

What is the ratchet stop on a micrometer for?

It slips once the spindle presses with a set force, so every measurement is taken at the same pressure.

What is the sleeve of a micrometer?

The fixed tube between the frame and the thimble, also called the barrel. It carries the main scale.

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