How to Convert a Metric Drill Bit to Standard

Written by bob white
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How to Convert a Metric Drill Bit to Standard
Converting the size of a drill bit requires a chart to reference. (Stockbyte/Stockbyte/Getty Images)

Mankind has used drills for thousands of years to create perfectly round holes in wood and steel. The first known mechanical drill was invented by the Egyptians and used a bow to turn the bit. The drill bits job is to auger the hole and remove the material. Drill bits come in a variety of sizes to assist with any job and maybe sized using the metric or imperial system. This information is engraved into the side of the bit.

Skill level:


  1. 1

    Hold the drill bit by its cutting end and rotate the bit until you see the engraving in its smooth end.

  2. 2

    Record the size measurements or designation number off the bit. The size looks something like ".508 mm" or "3/8" and the designation number appears like "#45."

  3. 3

    Click the link found in the resource section to the drill bit size chart. Locate the size of the bit using the columns, then look across to find the corresponding size in metric or imperial. Common sizes are: 1.5875mm = 1/16 inch, 3.175mm = 1/8 inch and 4.7625mm = 3/16 inch.

Tips and warnings

  • Always wear safety glasses when operating a drill. This keeps foreign objects from damaging your vision.

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