Micrometer screw gauge simulator
An interactive micrometer screw gauge for learning to read the sleeve and thimble scales to 0.01 mm. It's free to use, with no sign-up.
An object of unknown size is held in the jaws. Drag the slider to close the micrometer on it, read the scales, and enter the object's size.
The jaws are still open.
How to read a micrometer screw gauge
- Close the jaws gently on the object, using the ratchet so you don't squeeze it.
- Read the sleeve scale up to the edge of the thimble. Marks above the line are whole millimetres; marks below are half millimetres.
- Read the thimble scale at the line along the sleeve. Each of its 50 divisions is 0.01 mm.
- Add the two readings, then correct for any zero error.
For example, if the sleeve shows 2.5 mm and the thimble line is at 12 divisions, the reading is 2.5 + 0.12 = 2.62 mm. The thimble goes round twice for each whole millimetre, so check whether the half-millimetre mark is showing before you read the thimble.
Zero error and uncertainty
Close the jaws with nothing between them and check the reading. If it isn't 0.00 mm, that's the zero error. A positive zero error means every reading is too big, so subtract it; a negative one means they are too small, so add its size. Try the zero error option above for practice.
The uncertainty of a single reading is usually taken as ±0.01 mm. To find the diameter of a wire, measure in several places and at right angles, and take a mean.
Common mistakes
- Forgetting the half millimetre when the mark below the line is showing.
- Reading the thimble value in the wrong place - it is the line level with the sleeve's datum line.
- Applying the zero error the wrong way round.
- Squeezing the object instead of using the ratchet, which changes the reading.
Prefer a video? Watch a walkthrough on YouTube.
Frequently asked questions
- How do you read a micrometer screw gauge?
- Read the whole and half millimetres from the sleeve, up to the edge of the thimble. Then read the hundredths of a millimetre from the thimble scale, at the line along the sleeve. Add the two readings together.
- What is the resolution of a micrometer?
- A standard micrometer reads to 0.01 mm. The thimble has 50 divisions and one turn moves the spindle by 0.5 mm.
- What is a zero error on a micrometer?
- If the reading is not zero when the jaws are closed, the instrument has a zero error. Subtract it from every reading: a positive zero error means the readings are too big.
Practise it in a full required practical
LabWizard walks A-Level Physics students through simulated required practicals, from taking measurements with instruments like this one to graphing, analysis and exam questions. This skill is used in the Resistivity of a Wire, Young Modulus of a Wire practicals.
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