Measuring the O.D. of a tube

Monday, January 5, 2009 by admin.

This is the first in a series of occasional posts where I will address some the most frequently asked questions with regard to metal tube specifications.

Measuring the O.D. of a tube

As no metal tubing is perfectly round, all O.D. (outer diameter) measurements are average measurements.

The outer diameter of a tube is measured by the average of at least four measurements taken equally around the circumference of the tube.  A micrometer that is properly calibrated and cleaned will be used for this measurement.  A non-contact laser micrometer can also be used if one is available.

Using the face of a clock for orientation, the first measurement should be taken between 12:00 and 6:00, the next measurement between 1:00 and 7:00, then 3:00 and 9:00 and finally, 4:00 and 11:00.  All measurements must be recorded individually then added together and divided by the number of measurements to get the average O.D.  It is only after the average O.D. measurement is found the we can determine if the tube we are inspecting is within specification.

For more information on metal tubing visit our website at WWW.AdvancedTube.Com

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