Home >> Science & Nature >> Science

How to Determine the Concentricity of Tubing

Tubing is used in hospital rooms, dairy farms, and automobiles. The one thing absolutely necessary in tubing is that the liquid inside stay inside ̵2; and if the tubing is formed badly and a wall is too thin, the tubing can fail. Concentricity is a measure of how closely the inner and outer diameters line up with each other. If the diameters are perfectly centered, then the tubing wall is the same thickness all the way around. If the inner diameter is not centered, one side will be too thin. That̵7;s at the heart of the specification and measurement of concentricity.

Things You'll Need

Razor blade or utility knife
Tubing
Cardboard
Loupe or calipers

Instructions

- 1
  Lay the tubing flat on the cardboard. Slice downward with the razor blade or utility knife, and cut off the end to make it straight and clean. Once the end is clean, slice off a thin slice of tubing.
- 2
  Measure the minimum and maximum wall thickness using the calipers. Place the two jaws of the calipers lightly against the inner and outer walls of the slice you have cut. Measure at several places around the disk you have cut to be sure of finding the minimum and maximum thickness. For purposes of illustration, assume you measured a minimum of 0.095 inches and a maximum of 0.110 inches.
- 3
  Divide the minimum wall thickness by the maximum wall thickness. Multiply by 100 to get the concentricity in percent.
  The concentricity for the example measurements would be 100 x 0.095/0.110 = 86.4 percent.

Science