Magnet Pull Force Guide: How to Specify a Test

Magnet Pull Force: Test Conditions and Design Inputs

Numerical calculator under review

Pull-force output is temporarily unavailable while the calculation model is checked against defined test conditions. A number without a validated setup should not be treated as a holding-force rating or acceptance result.

For an engineering review, send the magnet shape and dimensions, grade or material, magnetization direction, steel grade and thickness, working gap or coating, pull direction, operating temperature, and the force you need at that position.

Send a drawing and request a quote. See Arnold Magnetic Technologies’ holding-force guidance for how surface condition, gap and steel saturation affect results.

A pull-force figure only means something when the test setup is defined. Steel thickness and grade, air gap, coating, pull direction, magnetization and temperature can change the result. This page explains those inputs and helps you prepare a drawing-based request. Numerical output is temporarily unavailable while the model is reviewed; use measured data from a defined setup when force is an acceptance requirement.

What does a pull-force number describe?

Pull force is the force measured when a magnet is separated from a specified target under a specified test setup. A straight pull from a flat steel plate is different from a shear load, a peeling motion, or the field required at a sensor’s working gap. Those results should not share one unqualified “magnet strength” value.

A calculator can be useful for comparing candidate dimensions, but only when its assumptions and validation are known. The previous numerical model on this page is under review. Until it is validated, this page does not supply a pull-force rating or a pass/fail value for a finished assembly.

Why the same magnet can give different results

Gap and surface: paint, plating, adhesive, roughness and imperfect flatness separate the magnet from the target. Even a small gap can lower holding force.
Steel target: its grade, area and thickness affect the magnetic circuit. Thin steel may saturate, so a thicker magnet need not deliver a proportionate increase.
Direction of loading: a normal pull, sliding load and peel force are different tests. A mounting design must be assessed in its real load direction.
Magnet and assembly: grade, geometry, magnetization direction, backing steel, temperature and nearby parts can change the result.

Arnold Magnetic Technologies’ holding-force guidance describes the effects of interface quality, coatings, steel saturation and pull direction. K&J Magnetics likewise explains that its calculator is an approximation supported by product tests and is not the sole basis for a design. Magnetstek’s earlier formula had no comparable documented calibration.

Specify the test before comparing magnets

For a useful supplier review, send a sketch or drawing with the following:

Magnet shape, finished dimensions, tolerances and magnetization direction.
Material or grade if already selected, plus the operating temperature and environment.
Target material, thickness, finish, and any coating or adhesive between the surfaces.
Working gap and the position at which field or force is required.
Load direction, target force, inspection method and quantity.

If the requirement is a motor or sensor, a pull-from-steel figure may be the wrong acceptance test. Specify the field at the actual working position or the assembly-level performance that the design needs. See the sensor magnet working-gap guide for an example.

Material choice follows the assembly requirement

NdFeB is one possible permanent-magnet family, but a higher N number is not a complete specification for pull force or service temperature. SmCo, ferrite and other materials may warrant review depending on the space, temperature, field and cost constraints. The grade, coating, magnetic circuit and acceptance test should be agreed for the particular part.

Send your drawing for a specification-based quote. Ask for a defined test method if pull force will be used for acceptance.

What We Review Before Quoting

Share your drawing, magnetic requirements and operating conditions. Magnetstek reviews grade, coating, magnetization and inspection options for each custom part.