How to Measure the Bore Size of Air Cylinders

Written by kennedi rose
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How to Measure the Bore Size of Air Cylinders
The interior diameter of a piston is its bore size. (cylindre et piston image by Unclesam from

The displacement of any piston and cylinder device is defined as the bore multiplied by the stroke length. If you know the stroke length of the piston -- meaning, if you know how far the piston moves up and down -- and if you also know how to measure the bore size, you will be able to use that knowledge to calculate the displacement.

Skill level:

Things you need

  • Calipers
  • Wrench

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  1. 1

    Measure the outside of the bore cylinder, using a set of calipers. This diameter will tend to overestimate the size of the bore, because of the thickness of the cylinder wall. This measurement will be sufficient if you only need a rough approximation.

  2. 2

    Remove the cylinder head if you need a more accurate measurement. Remove this by unbolting the four bolts that hold the cylinder head to the top of the cylinder. Use a wrench or ratchet.

  3. 3

    Insert the interior diameter measurement side of the caliper into the cylinder. Measure the diameter of the interior of the cylinder with the caliper. This is your bore size.

  4. 4

    Reassemble the cylinder head by bolting the cylinder head back onto the cylinder.

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