Micrometer and Vernier Callipers

Micrometer and Vernier Callipers

Micrometers

Overview

  • A micrometer is a highly precise measuring tool commonly used in design and technology.
  • It’s typically used to measure small dimensions to an accuracy of one thousandth of a millimetre (0.001mm).
  • It uses a spindle which is a precisely shaped cylinder for measuring both inner, outer and depth dimensions.
  • The main components of a micrometer include frame, anvil, spindle, lock and scale.

Use of Micrometers

  • Micrometers are typically used when the dimensions must be accurate and precise, commonly in metalworking and mechanical engineering.
  • They can measure a variety of objects, such as thickness of sheet materials and diameter of rods or spheres.

Reading a Micrometer

  • To read a micrometer accurately, take the readings from the main millimetre scale and add it to the rotational scale reading.
  • The main scale on the tool’s sleeve denotes millimetres (mm), while the rotational scale on the thimble denotes fractions of a millimetre.
  • The number that lined up with the datum line on the sleeve represents the measurement reading.

Vernier Callipers

Overview

  • Vernier callipers are also precise measuring instruments, but are typically less accurate than micrometers.
  • They have two jaws which can be adjusted across the object to be measured, providing flexibility in measuring various types of objects.
  • They come equipped with a main scale in centimeters and smaller vernier scale for more precise fractional readings.

Use of Vernier Callipers

  • Vernier callipers can measure external dimensions, internal dimensions and depths of objects.
  • They are commonly used in various forms of mechanical engineering, metalworking, forestry, and science and education for their versatility and ease of use.

Reading Vernier Callipers

  • The value of the reading is a combination of the main scale reading and the vernier scale reading.
  • To read it, first identify the zero mark on the vernier scale then see which vernier scale line aligns with a line on the main scale.
  • The number of aligned vernier scale line represents the fractional reading which is added to the main scale reading to get the final reading.

Comparison Between Micrometers and Vernier Callipers

  • In general, micrometers provide a higher level of accuracy and precision compared to vernier callipers.
  • Vernier callipers however, provide more versatility, as they can measure inside, outside, and depth of an object with one tool.
  • Choosing between the two often depends on the accuracy required and type of dimension being measured in the task.