How to Use a Caliper and a Micrometer
In this article, we will briefly explain how to correctly measure the outer diameter and wall thickness of a pipe.
To perform an accurate measurement, two measuring instruments are required:
- Micrometer
- Caliper (Vernier Caliper)
The micrometer is used to measure the wall thickness of the pipe, while the caliper is used to measure the outer diameter of the pipe.
Micrometer Caliper
How to Use a Micrometer – Measuring Pipe Wall Thickness
- Loosen and open the micrometer according to the approximate wall thickness of the pipe.
- Place the two measuring ends of the micrometer on a section of the pipe that does not coincide with the inner burr.
- Avoid measuring from the inner burr area because the wall thickness there will appear thicker on a burr-included pipe and thinner on a deburred pipe, which would result in an inaccurate reading.
- Stop tightening the micrometer as soon as the thimble resistance is first felt. Do not overtighten — just tighten until the micrometer gently grips the pipe wall.
- Read the scale on the horizontal line first.
- Each lower line represents 0.5 mm, and each upper line represents 1.0 mm. Note the number of lines passed.
- Then, read the vertical line, where each division represents 0.01 mm. Note the number of divisions passed.
- Add the two readings together to obtain the wall thickness in millimeters.
Example:
If the horizontal scale shows 3.00 mm and the vertical scale shows 0.03 mm, the total wall thickness is:
3.00 mm + 0.03 mm = 3.03 mm.
How to Use a Caliper – Measuring Pipe Outer Diameter
- Place the pipe between the jaws of the caliper so that it grips the widest point (the true outer diameter).
- Read the upper scale first — this is in millimeters, with each line representing 1 mm. This value forms the integer part (to the left of the decimal point).
- Next, read the lower scale (Vernier scale) — each division here represents 0.1 mm, and each small line represents 0.05 mm.
- The upper lines correspond to 0.025 mm.
- The point where a line on the lower scale aligns exactly with a line on the upper scale indicates the decimal part (to the right of the decimal point).
- Add both readings together to obtain the pipe’s outer diameter.
Example:
If the upper scale shows a value between 26 mm and 27 mm, and the lower scale shows alignment at the 6th mark, then:
26.00 mm + 0.60 mm = 26.60 mm.
And that’s how easily you can measure a pipe’s outer diameter!
