How to Use the Expanding Mandrel

Written by jane humphries
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How to Use the Expanding Mandrel
An expanding mandrel connects to a lathe. (Stockbyte/Stockbyte/Getty Images)

An expanding mandrel is a tool used for holding a machined component part ready for milling, grinding or quality inspection. Commonly, an expanding mandrel attaches to a lathe so that the unfinished part rotates while you use secondary machining to finish the surface. The mandrel consists of a tapered arbor, or shaft, with a slatted sleeve that expands to fit the internal bore of the component. The design of the expanding mandrel makes it possible to uniformly clamp the machined part from the inside so that the outer surface is free to work on.

Skill level:

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Things you need

  • Lathe
  • Machined component part
  • Flat piece of wood
  • Safety goggles
  • Protective clothing

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  1. 1

    Switch off the lathe to ensure your safety when changing the chuck settings. Remove any tooling that is in the lathe chuck. Pull the sleeve off the expanding mandrel's arbor shaft and set the arbor to one side.

  2. 2

    Slide the machined part onto the expanding mandrel sleeve so that it fits snugly but not too tight. Choose a smaller diameter sleeve if you find that you have to force the part onto the sleeve. Choose a larger diameter sleeve if you find the part slides loosely along the sleeve.

  3. 3

    Insert the tapered end of the arbor into the wider opening on the sleeve. Push the arbor through the sleeve's central core until the sleeve clamps onto the arbor.

  4. 4

    Tap the wider base of the arbor firmly onto a flat piece of wood so that the sleeve clamps tightly around the arbor shaft. Insert the wide end of the arbor into the lathe chuck and fasten securely.

  5. 5

    Switch on the lathe. Choose the lathe rotation speed you require for your machining or component part inspection. Carry out the inspection or machining on the surface of the part.

  6. 6

    Switch off the lathe, and remove the arbor from the lathe chuck. Tap the tapered end of the arbor onto the flat piece of wood to loosen the expanding mandrel sleeve. Pull the sleeve off the arbor shaft, and slide the finished component part off the sleeve.

Tips and warnings

  • Wear safety goggles and protective clothing when operating a lathe to avoid injury from grinding debris.

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