Air Power – Vacuum Chucks for Workholding

I used to keep a roll of double-back adhesive tape at the bottom of my toolbox. Whenever I took the tape out, my fellow machinists would run for shelter. Why? Because I made chucks for holding thin workpieces from it, and I guess something bothered them about the combination of tape, machinery and cutting tools.

Whatever my co-workers may have thought at the time, my idea wasn’t that crazy. Thin parts are difficult to hold onto. But now I know a better way to secure them than with tape: vacuum chucks.

Others are aware of the benefits vacuum workholders offer, too. Manufacturers in the sheet metal, cabinet and computer-chip industries use vacuum chucks every day.

It’s doubtful, though, that many owners and managers of machine shops consider vacuum workholding systems a viable method for securing parts. They should. Vacuum chucks are good for machining the following:

  • Thin and irregularly shaped parts that are difficult to hold in a vise.
  • Workpieces made of aluminum and materials that mar easily.
  • Large, flat parts that would require too many clamps if held by conventional means.
  • Small parts that can be “nested” on one piece of material, allowing them to be machined in a single setup.

A vacuum chuck can generate hundreds of pounds of holding force, with the actual amount dependent upon the workpiece surface area exposed to the chuck. The maximum force that any vacuum-generating source can produce is 14.7 psi. So, under ideal conditions, the force holding a 10″x10″ workpiece whose entire face contacts the chuck would be 1,470 lbs.

True, that holding force pales in comparison to what a mechanical chuck could supply. But if you regularly machine parts that are tough to secure by conventional methods, you might consider tapping into vacuum power.

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