How to measure hydraulic fittings

Written by mary lougee
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How to measure hydraulic fittings
Hydraulic fittings attach hoses to components. (hydraulic hose image by Alex White from

Hydraulic fittings are available in various sizes to connect hoses on components and deliver hydraulic fluid to them for power. Heavy equipment such as dump trucks and backhoes use hydraulic energy to extend truck beds so they dump and backhoe arms so they can dig. The measurements needed to fit a hydraulic fitting correctly are the length, exterior diameter, inside diameter, thread gauge and angle of the fitting.

Skill level:

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Things you need

  • Measuring tape
  • Calipers
  • Pitch gauge
  • Protractor

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  1. 1

    Lay the hydraulic hose fitting on a flat surface such as a table or workbench. Stretch a measuring tape out on top of the fitting and measure the length of the metal fitting.

  2. 2

    Slide the top screw on the calipers to the front of the tool to zero it out. Open the jaws by sliding the top screw backward and place the calipers on the outside of the fitting. Slide the caliper jaws together to touch the outside of the fitting in between the caliper jaws. Read the main scale at the top first in hundredths where the first marking falls between two marks. Then add the number on the bottom scale that's perfectly aligned with a mark on the sliding scale. For example, if the first mark falls between 1.2 and 1.3, and the bottom scale has the number 3 perfectly aligned with the sliding scale, the reading is 1.23. This is the inside diameter of the fitting.

  3. 3

    Measure the inside diameter of the fitting by placing the small jaws of a caliper inside the fitting and pushing the jaws out so they both contact the internal measurement. Read the size in the same manner as reading the outside diameter.

  4. 4

    Place a pitch gauge on the threads of the fitting. The correct pitch gauge has small teeth that fit perfectly into the threads of the fitting. Use a smaller or larger gauge to find the correct fit and read the size on the gauge for the measurement. The pitch gauge measures threads per inch.

  5. 5

    Place each tip of a protractor on an angled fitting with the tip in the centre of each portion. Read the numbers that align on the protractor for the angle measurement of the fitting.

Tips and warnings

  • English thread gauges are marked in threads per inch; metric thread gauges are marked in distance between threads in millimetres.

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