Mechanical Magnetic Chuck for CNC Machines – Functions & Working Principle

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1. Functions of a Mechanical Magnetic Chuck

A mechanical magnetic chuck (permanent magnetic chuck with manual control) uses the magnetic force of permanent magnets to secure ferromagnetic workpieces (steel, cast iron, etc.) on CNC machines.

Main functions:

  • ???? Quick clamping without vises or bolts

  • ???? High flatness and repeatability, suitable for finishing operations

  • ???? Allows machining of bottom surfaces and edges due to an open clamping surface

  • ⚡ No electrical power required, safe during power loss

  • ⏱️ Shorter setup time, increased productivity

Typical applications:
CNC milling, CNC surface grinding, mold & die machining, thin or large flat workpieces.

Basic structure:

  • Permanent magnets (Ferrite or NdFeB)

  • Alternating North–South magnetic poles

  • Pole plate (magnetic steel top plate)

  • Mechanical rotating/sliding magnet mechanism (ON/OFF lever)

Two operating states:

???? ON state (clamping):

  • The lever is turned to ON

  • Magnets change position

  • Magnetic flux is directed upward to the chuck surface

  • Flux passes through the workpiece
    → Strong holding force is generated

???? OFF state (release):

  • The lever is turned to OFF

  • Magnetic flux is closed inside the chuck body

  • No flux passes through the workpiece
    → The workpiece can be removed easily

???? Key point: The magnets are always active; the system controls the magnetic flux path, not the magnet itself. No electricity is involved.

3. Advantages and Limitations

Advantages

  • ✅ High safety, no heat generation, no vibration

  • ✅ Uniform clamping force over the entire surface

  • ✅ Ideal for thin workpieces (minimal deformation)

  • ✅ Long service life, low maintenance

Others