How Magnet Pull Force Is Measured (And Why It Varies)

Magnet pull force ratings are often misunderstood. Published pull force values represent the maximum force required to separate a magnet from a thick, flat, low-carbon steel plate under ideal laboratory conditions.

In real-world applications, actual holding strength may be significantly lower depending on installation and environmental factors.

How Pull Force Is Tested

Standard pull force testing typically involves:

• Direct contact between the magnet and steel surface
• Thick, flat, low-carbon steel plate (often 10mm or more)
• Perpendicular pull direction
• Slow, controlled separation force

This test setup maximizes magnetic circuit efficiency and produces the highest measurable value.

Why Real-World Performance Varies

In practical applications, several factors reduce holding strength:

• Air gap caused by paint, coating or debris
• Thin steel surfaces
• Curved or uneven mounting surfaces
• Shear (sliding) forces instead of direct pull
• High operating temperatures

Even a small air gap can significantly reduce magnetic performance.

Pull Force vs. Shear Force

Pull force refers to direct separation force perpendicular to the surface. In many installations, magnets experience shear force (sliding force), which is typically much lower than rated pull strength.

Proper mechanical support is recommended in safety-critical applications.

Steel Thickness Matters

If the steel surface is too thin, it cannot fully carry the magnetic flux. This limits the achievable holding force regardless of magnet grade.

Thicker, low-carbon steel provides optimal performance.

Choosing the Right Magnet

Understanding pull force testing helps avoid overestimating performance. Selecting the correct magnet size, grade and mounting configuration is essential for reliable results.

If you need assistance evaluating pull force requirements, our team can provide technical guidance tailored to your application.

Related Resources

Learn more about neodymium magnet grades explained or explore our Industrial Neodymium Magnets in Canada product range.