How to convert a metric feeler gauge to standard

Written by c.l. rease
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How to convert a metric feeler gauge to standard
Feeler gauge blades are either sheet metal or wires. (gauge , background, colour image by Greg Pickens from

Correct measurements of any tight tolerances are a necessity to ensure the proper operation of your mechanical and electrical equipment. Feeler gauge blades have the width -- in metric or standard units -- of the blade stamped near their base. When using a feeler gauge with only metric sizes stamped on the blade, you can still determine the standard size by converting the metric dimension. A simple mathematical equation allows you to precisely convert a metric dimension to a standard equivalent.

Skill level:

Things you need

  • Metric feeler gauge
  • Mechanical gap
  • Calculator

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  1. 1

    Slide one blade of a metric feeler gauge into a mechanical gap to determine the gap width. The correct blade will slide into the gap while slightly contacting the top and bottom of the gap.

  2. 2

    Read the number stamped on the bottom of the feeler gauge blade matching the size of the mechanical gap.

  3. 3

    Enter the metric measurement into a calculator. Multiply the metric number by 0.039 to convert the metric dimension to standard units. For example, a feeler blade 3mm thick multiplied by 0.039 equals 0.117 or 3/32 inch.

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