How to true a three-jaw metal lathe chuck

Written by jeremiah blanchard
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How to true a three-jaw metal lathe chuck
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A three-jaw chuck is used as a clamping device for holding a work-piece or a rotating tool at a specific position. This tool is commonly used in conjunction with a metal lathe by machinists. Over time, the chuck jaws can become worn, resulting in knocking the chuck out of "true" on the lathe. In order for the chuck to be used accurately for machine work, the jaws must be "trued," or recalibrated, to fit the lathe.

Skill level:

Things you need

  • Endmill
  • Drill press
  • Carbide-tip boring bar or metal grinder
  • Fine metal file

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  1. 1

    Load the jaws into the chuck in the same way that you would normally use them for your project specs.

  2. 2

    Cut a 1/4-inch-thick steel plate to the same diameter as the chuck using an endmill.

  3. 3

    Drill a hole through the centre of the steel plate to match the diameter of the hole in the chuck. A metal drill press is ideal to use for this step.

  4. 4

    Drill the three jaw holes onto the plate in the same pattern as they appear on the chuck. You can make a template for the hole placement out of cardboard to ensure accurate drilling.

  5. 5

    Remove any burring from cutting or drilling with a fine metal file. Slip the metal plate over the jaws. Re-bore the jaws using a carbide-tip boring bar or a metal grinder using the metal plate as a guide. After the jaws are rebored, the jaws will be "true" for your lathe.

Tips and warnings

  • Lubricate the chuck jaws often to prevent grinding that results in the "untrueing" of the chuck jaws.
  • Always wear adequate eye protection when using metal machine tools.
  • Never place your hands near a metal lathe, drill press or endmill while in operation.

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