The right magnet depends on what the magnetic system must actually do. A holding magnet is selected differently from a sensor target, motor rotor magnet, magnetic coupling or high-temperature permanent magnet. Instead of starting with the strongest grade, start with the functional requirement: force, field, torque, position sensing, temperature, air gap, environment and available space.
This guide organizes magnet selection by application. For a detailed NdFeB sourcing checklist covering grade, coating, magnetization, tolerances and documentation, use the Neodymium Magnet Procurement Guide.
Magnet Selection by Application
| Application | What matters most | Common magnet approach | Best next resource |
|---|---|---|---|
| Holding / latching | Breakaway force, air gap, target steel, shear | Disc, block, countersunk or pot magnet | Pull Force Calculator |
| Position / speed sensing | Field at sensor, polarity, orientation, working gap | Disc, cylinder, ring, diametric or multipole | Sensor Magnet Guide |
| Electric motors | Air-gap flux, Br, HcJ, temperature, pole pattern, retention | Arc segments, blocks, radial/multipole rings | Motor Magnet Guide |
| Magnetic couplings | Torque, gap, barrier thickness, pole count, temperature | Opposed discs, ring arrays, segmented rotors | Magnetic Couplings Guide |
| High-temperature service | HcJ, operating point, Pc, peak temperature | Higher-coercivity NdFeB, ferrite, Alnico or other qualified material | Heat-Resistant Magnets |
| Corrosive / humid environment | Coating integrity, chemicals, moisture, test requirements | Qualified coating system or naturally corrosion-resistant material | Epoxy-Coated NdFeB Guide |
Holding and Latching Magnets
For holding, mounting and latching, the important number is not simply the magnet grade. Real holding force depends on the magnet geometry, steel target, contact area, air gap, surface finish and whether the load is tensile or shear.
Catalog pull-force values are test results under defined conditions and should not be treated as universal safe working loads. Paint, coatings, thin sheet steel, curvature, misalignment and shear can reduce usable force substantially.
Use the Magnet Pull Force Calculator and Pull Force Explained when sizing a magnet-to-steel assembly. For mounting hardware, browse pot magnets.
Sensor and Encoder Magnets
For Hall-effect, TMR, AMR, GMR and rotary-position sensors, field at the sensor location is usually more important than pull force. Define the required flux density, polarity, vector direction, air gap and travel range before choosing the magnet.
Diametrically magnetized discs or cylinders are common in rotary angle sensing because the field vector rotates with the shaft. Multipole rings are useful when repeated pole transitions or higher-resolution incremental sensing is required.
See Sensor Magnets for Hall, TMR & AMR, the Field Distance Calculator, and Radial vs. Diametric Magnetization.
Electric Motor and Rotor Magnets
Motor magnets must be selected around the complete magnetic circuit. Important factors include air-gap flux, rotor topology, pole count, temperature, opposing stator field, demagnetization margin, mechanical retention and production tolerances.
A higher room-temperature grade is not automatically better. In a hot rotor or strong reverse field, a higher-coercivity grade can be more appropriate than a higher-Br standard grade.
Use the Magnets for Electric Motors guide, the Demagnetization Calculator, and the Neodymium Grade Chart.
Magnetic Couplings
Magnetic couplings transmit torque through a gap or nonmagnetic barrier without a direct shaft penetration. Selection should consider target torque, RPM, coupling diameter, pole count, working gap, barrier material/thickness and temperature.
Torque can change rapidly with separation and geometry, so pull force is not a substitute for coupling analysis. See Magnetic Couplings for Pumps & HVAC and the Magnetic Coupling Torque Calculator.
High-Temperature Magnet Applications
Temperature selection requires more than checking a single published maximum-operating-temperature number. The magnet grade, intrinsic coercivity (HcJ), geometry, permeance coefficient, magnetic circuit and opposing field determine irreversible-demagnetization margin.
For NdFeB, suffixes such as M, H, SH, UH, EH and AH identify different coercivity/temperature classes, but the actual design still needs application-specific validation.
Use Heat-Resistant Magnets, the Temperature Derating Calculator, and the Demagnetization Calculator.
Humid, Outdoor and Corrosive Environments
Sintered neodymium normally requires corrosion protection. Ni-Cu-Ni is common for general-purpose use, while epoxy and other systems may be selected when the environment requires additional protection.
No coating should be assumed to be universally waterproof, chemically resistant or suitable for a regulated end use without qualification. If immersion, salt spray, sterilization, cleaning chemicals or adhesive bonding matter, specify the exact exposure and test requirement.
See Epoxy-Coated Neodymium Magnets and Magnet Coatings Compared.
When Ferrite May Be Better Than Neodymium
Ferrite can be a better fit when the design has sufficient space and priorities include lower material cost, excellent corrosion resistance and high-volume production. NdFeB is usually favored when the magnetic requirement must fit into a smaller package.
Use the Ferrite vs. Neodymium comparison or browse ferrite/ceramic magnets.
What Every OEM Magnet Specification Should Define
- Functional requirement: field, force, torque or sensing threshold
- Working distance or air gap
- Material and grade, if already determined
- Geometry and dimensional tolerances
- Magnetization direction or pole pattern
- Continuous and peak operating temperature
- Coating and environmental exposure
- Inspection method and acceptance limits
- Annual volume and packaging
- Traceability, COC, PPAP or compliance documentation when required
If the required part may already exist, search Radial Magnets inventory. For engineered or production requirements, use the Magnet RFQ Builder or Bulk Magnet RFQ.
