Measuring Pull Strength

By Shalea Hardison

One method of determining magnet strength is through pull strength, or a pull test.

Pull strength is a reliable method of measuring the maximum strength, or holding power, a magnet has before it breaks away from a ferrous material. It is measured in pounds or kilograms.

Magnetic assemblies are measured by the pounds of pull in a vertical test. The higher the pull strength, the stronger the magnet. Permanent magnetic materials are commonly measured by grade. For more information about magnet grades, refer to the post Understanding Magnet Grades.

The Process

Master Magnetics rates our magnetic assemblies by pounds of pull in a vertical test. Each magnet’s entire magnetic surface is tested against a half-inch thick, ground steel plate. Beginning with a clean magnetic surface and a clean steel surface, the magnetic assembly is attached to the steel plate. A hook with the measuring device is attached to the magnet and it slowly pulls the magnet upward until enough force to break the magnet away from the plate is created.

The measuring device records the pounds pull. Repeated measurements establish an accurate reading and pounds pull rating for each magnetic assembly.

Pull tests are widely used across the magnetic industry. Pounds pull ratings are common for magnetic assemblies, providing users with accurate insights into each product’s capabilities.

However, pull strength will vary due to:

• differing thicknesses of steel (particularly less than a half inch)
• types of steel composition
• coatings on the steel, including paint or grease
• or uneven surface area, such as rust

Watch a video about pull testing.

Application Considerations

Choosing a magnetic assembly might be as straightforward as selecting the right pounds pull for your application. Other considerations include how many poles are needed; if it there will be air gaps at any point on contact; the temperature of the environment; and the storage area. All of these can affect the type of magnet best suited to a project.

We always recommend consulting with one of our Magnet Experts for assistance in the selection of the best magnet for your needs.