Grinding Permanent Magnets: Choosing the Right Grinding Wheel

Permanent magnets such as NdFeB, SmCo, Ferrite, and AlNiCo are widely used in modern industries—from electric motors and wind turbines to sensors, consumer electronics, and medical devices. In the manufacturing process of these magnets, precision grinding is a key step to achieve the required tolerance, flatness, and surface quality. Selecting the correct grinding wheel is therefore critical.

1. Why Grinding Permanent Magnets is Challenging

Permanent magnets are generally hard, brittle, and sensitive to heat. For example:

• NdFeB (Neodymium Iron Boron): very hard and prone to chipping; also easily oxidized.

• SmCo (Samarium Cobalt): extremely brittle, requires careful cutting.

• Ferrite: ceramic-like, brittle, but lower cost.

• AlNiCo: metallic, less brittle, but with high toughness.

These characteristics make ordinary abrasives unsuitable. Instead, superabrasive grinding wheels are required.

2. Recommended Grinding Wheels for Different Magnet Materials

• NdFeB and SmCo Magnets

  • Grinding wheel: Diamond grinding wheel

  • Bond type: Resin bond for fine grinding and reduced chipping; vitrified bond for high efficiency and shape holding.

  • Application: Suitable for block magnets, ring magnets, and arc segments.

• Ferrite Magnets

  • Grinding wheel: Diamond grinding wheel

  • Bond type: Resin or vitrified bond, depending on production requirements.

  • Application: Common for loudspeaker magnets, motor stator/rotor magnets.

• AlNiCo Magnets

  • Grinding wheel: CBN (Cubic Boron Nitride) grinding wheel or Alumina grinding wheel

  • Bond type: Vitrified or resin bond.

  • Application: Effective for cutting and grinding metallic magnets with less brittleness.

👉 General rule:

• Hard and brittle magnets → Diamond grinding wheel.

• Metallic magnets (AlNiCo) → CBN or Alumina wheel.

3. Suitable Grinding Machines

Permanent magnet grinding usually employs:

• Surface grinders (for blocks, wafers, and small pieces).

• Double-disc grinders (for high-precision thickness and parallelism control).

• Cylindrical or centerless grinders (for rings and round magnets).

• Form grinders (for arc or special-shaped magnets).

4. Key Considerations During Grinding

• Always demagnetize before grinding to avoid chips sticking to the workpiece.

• Use non-magnetic fixtures (vacuum chuck, resin fixtures, etc.).

• Apply sufficient coolant to prevent heat damage and oxidation.

• Ensure wheel dressing is frequent to maintain sharpness and minimize chipping.

5. Conclusion

Choosing the right grinding wheel is essential for achieving precision, efficiency, and surface quality in permanent magnet production. Diamond grinding wheels are the preferred choice for NdFeB, SmCo, and Ferrite magnets, while CBN wheels are recommended for AlNiCo magnets.

As a professional manufacturer of superabrasive tools, we provide customized diamond and CBN grinding wheels designed specifically for magnet machining. With stable quality and strong production capacity, we support overseas partners in motor, electronics, and renewable energy industries.

Tip: Hard and brittle magnets → Diamond; Metallic (AlNiCo) → CBN or Alumina.