How does the micrometer and vernier caliper work?

Answer 1

The basic idea is that such devices maintain higher tolerances than can be perceived by the human eye directly, so a mechanical device such as a screw or a 10% amplified scale that aligns with the regular scale at the right point is used to make small changes more apparent to the eye.

Answer 2

The micrometre uses a threaded rod with forty threads per inch, it advances 25 thousands of an inch in full turn of the shaft, there is a delicate ratchet built into the device to prevent over tightening, when the shaft is turned until the moving part touches the anvil, the scale will read 0. Anything within the size range of the instrument is measured by closing the gap until the ratchet clicks, then the diameter of the object is read from the scale. The vernier calliper has no turning barrel or ratchet, the jaws are simply closed until a light contact is made, the measurement is read from a calibrated scale on the frame of the calibre.

Answer 3

Check the following sites:
http://en.wikipedia.org/wiki/Caliper#Vernier_calipers
http://en.wikipedia.org/wiki/Micrometer
Much easier to understand than if it were just explained without illustrations. Click on caliper or micrometer for closeup views. ...Good Luck...