A Complete Guide to Standard Pull Force Measurements
In magnetic engineering, one of the most common questions is: “How strong is this magnet?”
Whether the application involves workholding, magnetic mounting, mechanical retention, or consumer product closures, Pull Force remains the most direct and comparable performance metric.
However, the actual pull force of a magnet can vary dramatically under different testing conditions. To obtain meaningful, repeatable data, it is essential to test magnets using standardized and well-defined methods.
This article summarizes the four industry-recognized testing scenarios (Case 1–4), along with simplified engineering sketches, to help you understand how to measure magnetic pull force correctly and how to interpret the results.
What Is Pull Force?
Pull Force refers to the maximum perpendicular force required to separate a magnet from an attached surface. It is also known as the breakaway force or holding force.
Although this is the simplest magnetic parameter to measure, it is also one of the most misunderstood—
the same magnet can show very different pull-force values depending on the test setup.
This is why standardized testing conditions are essential.
Four Standard Test Scenarios (Cases 1–4)
The table below summarizes the four common industrial testing conditions, including definitions, procedures, and engineering relevance:
| Case | Definition | Test Procedure | Engineering Value |
|---|---|---|---|
| Case 1 | A magnet attached to a large steel plate | Press the magnet against a sufficiently large and thick steel plate. Use a force gauge to pull the magnet off vertically. Record the peak force and average multiple trials. | Widely used industry baseline; best reflects magnets attached to steel surfaces, panels, housings, and fixtures. |
| Case 2 | Magnet clamped between two steel plates (steel–magnet–steel) | Sandwich the magnet tightly between two thick steel plates. Ensure full contact and alignment. Pull vertically and record the breakaway force. | Simulates closed magnetic circuits found in clamps, lifting systems, and industrial magnetic tooling. |
| Case 3 | Magnet-to-magnet attraction | Place two identical magnets face-to-face. One is fixed, the other connected to a pull gauge. Pull apart vertically and record peak force. | Represents cases where magnets in consumer or industrial products attach directly to each other. |
| Case 4 | Magnet-to-magnet repulsion (same pole facing) | Measure the maximum repelling force as two identical magnets with like poles approach each other. Typically verified with physical tests plus analytical or FEM simulation. | Used in magnetic levitation, compliant mechanisms, and applications requiring a defined repulsive force curve. |
Why the Four Cases Produce Different Pull Forces
Case 1 — The Industry Baseline
A thick, low-carbon steel plate allows magnetic flux to flow efficiently without saturating, producing stable and repeatable results. This is the default benchmark for most suppliers.
Case 2 — Usually the Highest Pull Force
With steel on both sides, the magnetic circuit becomes fully closed, maximizing flux utilization. Pull force can exceed Case 1 by 20–200%, depending on magnet geometry.
Case 3 — Critical for Consumer Product Design
Many real-world assemblies involve magnet-to-magnet contact rather than magnet-to-steel contact. Case 3 accurately represents magnetic clasps, magnetic covers, and magnetic pairs in assemblies.
Case 4 — The Most Complex to Characterize
Repulsive force varies steeply with distance, and the peak often occurs at very small gaps. Engineers typically combine physical testing with finite-element simulation (FEM) to obtain accurate force curves.
Key Factors That Influence Pull-Force Measurements
Regardless of the test case, the following variables significantly affect the measured force:
- Steel plate thickness
Thin steel saturates easily and reduces holding force.
- Material type
Low-carbon steel performs best; stainless steel (304/316) may dramatically reduce pull force.
- Surface quality
Paint, coatings, rust, and scratches reduce effective contact area.
- Air gap (even microscopic)
A 0.1 mm gap can reduce pull force by 5–50%, depending on magnet size.
- Magnet coating
Nickel or zinc coatings are hard and thin; rubber, epoxy, or plastic coatings introduce unavoidable gaps.
- Temperature
Neodymium magnets lose strength as temperature rises, especially grades like N52.
How to Choose the Correct Test Case for Your Application
| Application Type | Recommended Case | Reason |
|---|---|---|
| Magnet mounted on steel surfaces, housings, metal panels | Case 1 | Best reflects real single-surface attachment. |
| Magnetic clamps, lifting tools, double-sided fixtures | Case 2 | Reproduces closed magnetic circuits and clamping forces. |
| Products involving two magnets attracting each other | Case 3 | Most product designs use magnet-to-magnet contact. |
| Magnetic levitation, thrust mechanisms, repulsion-based systems | Case 4 | Requires accurate repulsive force characteristics. |
Summary: Building a Reliable Magnet Strength Testing Standard
To obtain repeatable and comparable pull-force data, you should:
- Define the test case clearly (Case 1–4).
- Standardize steel plate size, thickness, and material.
- Eliminate or minimize air gaps.
- Perform multiple trials and average the results.
- Use FEM simulations for repulsive-force or non-contact applications.
For engineers and buyers, pull force is only meaningful when the testing conditions are clearly specified. With standardized procedures, magnet performance becomes predictable and directly comparable across products and suppliers.
