How to Select the Right Neodymium Magnet: A Procurement Guide
Neodymium magnets provide very high magnetic strength relative to their size, but selecting the right part requires more than choosing the highest grade number. Procurement teams need to define the operating temperature, dimensions, tolerances, magnetization, coating, magnetic circuit, quality records and supply requirements before comparing quotes.
This guide provides a practical specification process for industrial and OEM sourcing.
The Short Answer: Define These Eight Requirements
- Required magnetic performance
- Maximum and normal operating temperature
- Shape, dimensions and functional tolerances
- Magnetization direction and pole configuration
- Working air gap and surrounding magnetic circuit
- Environmental and corrosion exposure
- Mechanical loads and assembly method
- Quality, traceability and regulatory documentation
If you already have these inputs, the fastest next step is the Magnet RFQ Builder.
Step 1: Select the Right Neodymium Grade
Commercial sintered NdFeB grades are commonly identified as N35, N42, N48, N52 and similar designations. Suffixes such as M, H, SH, UH, EH and AH identify higher intrinsic-coercivity classes used where greater resistance to irreversible demagnetization is needed.
The highest grade is not automatically the best choice. A lower-energy, higher-coercivity material may perform more reliably in a hot or demagnetizing environment. Compare Br, HcB, HcJ, BHmax and temperature classes in our Neodymium Magnet Grades, Properties & Temperature Limits chart.
If N52 is appropriate for the design and you are sourcing a standard part, browse all N52 neodymium magnets rather than starting from a single size. The N52 category is the primary commercial page for available N52 disks, blocks, rings and metric sizes.
For a practical explanation of those values, read How to Read a Magnet Datasheet.
Step 2: Specify the Actual Operating Temperature
The magnet’s real operating temperature may be higher than ambient because of motor windings, electronics, friction, solar load, sterilization, restricted airflow or heat conducted through the assembly. Specify normal operating temperature, maximum continuous temperature, short-duration peaks and expected thermal cycling.
Temperature capability depends on grade, geometry and magnetic circuit—not only the suffix printed on a catalog page. Use the engineering calculators and temperature tools during selection.
Step 3: Define Shape, Dimensions and Tolerances
Neodymium magnets are commonly produced as discs, cylinders, rings, blocks, arcs, countersunk parts and custom-machined geometries. A complete drawing should define finished dimensions, units, tolerances, chamfers or radii, flatness or concentricity where necessary and whether the stated dimensions apply before or after coating.
Avoid unnecessarily tight tolerances. Sintered NdFeB is hard and brittle, and tighter dimensions can require additional grinding and inspection without improving the finished assembly.
For standard geometries, search our inventory by size, grade or SKU before specifying a custom part.
Step 4: State the Magnetization Direction
Magnetization direction is one of the most expensive purchasing details to omit. Common configurations include axial, diametric, through-thickness, through-width, radial and multipole magnetization.
The drawing should show the required direction with an arrow or pole designation. If the assembly requires a specific north-pole orientation, indexed pole pattern or custom multipole configuration, include that requirement explicitly.
Step 5: Evaluate the Complete Magnetic Circuit
A magnet’s field and force depend on more than grade. Performance changes with magnet dimensions, air gap, mating-steel thickness, steel saturation, nearby magnets, temperature, pole-piece geometry and load direction.
If the application needs one-sided flux, reduced stray field, higher air-gap field concentration or a more sinusoidal rotor field, evaluate whether a Halbach array is more appropriate than a conventional alternating-pole assembly. Use the Halbach Array Visualizer to compare linear and circular patterns before defining a custom assembly. For sourcing, specify the array envelope, working gap, target field, temperature, segment count or wavelength, and whether you need loose segments or a completed bonded/sleeved assembly.
Surface Gauss vs. Pull Force
Surface gauss is magnetic flux density measured at a defined point. Pull force is a mechanical separation force measured using a specific fixture, target steel and test condition. They are not interchangeable.
Use the Technical Resource Hub for pull-force, grade and geometry tools, and define the actual test setup whenever magnetic acceptance criteria are part of the purchase order.
Step 6: Choose a Coating for the Environment
Sintered neodymium normally requires a protective finish. Common options include nickel-copper-nickel, epoxy, zinc, phosphate, parylene and specialty systems.
Coating selection should consider humidity, salt exposure, chemicals, cleaning agents, abrasion, electrical requirements, adhesive compatibility and expected product life. When corrosion performance matters, specify the coating system and acceptance requirement rather than writing only “nickel plated.”
Step 7: Account for Mechanical Properties
Neodymium magnets are magnetically strong but mechanically brittle. They can chip or crack from impact, aggressive interference fits, uneven clamping or uncontrolled snap-together forces.
- Use appropriate assembly clearance
- Prevent uncontrolled magnet-to-magnet impact
- Distribute clamping loads evenly
- Use adhesives compatible with the selected coating
- Add mechanical retention where bond failure would create a safety or reliability risk
- Tell the supplier about shock, vibration, rotation or centrifugal loading
Step 8: Define Quality and Compliance Documentation Before Ordering
Documentation requirements should be established during the RFQ, not reconstructed after shipment. Depending on the program, buyers may request:
- Certificate of Conformance
- Material certification
- Dimensional inspection report
- Magnetic-property or pull-force test data
- Coating documentation
- Lot traceability
- RoHS and REACH/SVHC declarations
- Conflict Minerals / CMRT or EMRT
- PFAS or California Proposition 65 status
- Country-of-origin documentation
- PPAP documentation
Review the Magnet Compliance Document Center and our quality and PPAP capabilities before supplier qualification.
Step 9: Plan Shipping, Packaging and UN 2807 Screening
Strong permanent-magnet shipments can require special packaging or magnetic-field screening for air transport. Do not assume a magnet is automatically regulated as UN 2807 based only on grade or pull force; classification depends on the measured external magnetic field of the prepared package under the applicable transport rules.
If air shipment is possible, review our Shipping Magnetized Material: UN 2807 & IATA PI 953 Guide and tell the supplier about the intended shipping mode, package configuration and destination before the order ships.
Neodymium Magnet RFQ Checklist
| Requirement | Information to provide |
|---|---|
| Material / grade | NdFeB grade plus minimum magnetic properties where critical |
| Shape / dimensions | Finished geometry, units and drawing revision |
| Tolerances | Functional dimensional and geometric tolerances |
| Magnetization | Direction, pole orientation and number of poles |
| Coating | Finish, thickness or environmental requirement |
| Temperature | Normal, maximum, minimum and exposure duration |
| Magnetic acceptance | Br/HcJ/BHmax, flux, gauss, pull force or other criterion |
| Environment | Humidity, chemicals, salt, vacuum, sterilization or other exposure |
| Quantity | Prototype quantity, production order size and annual demand |
| Documentation | CoC, inspection, traceability, regulatory declarations or PPAP |
| Shipping / packaging | Air, ocean or ground shipment; packaging constraints; UN 2807 / external-field screening if applicable |
How Should Procurement Teams Compare Magnet Suppliers?
Price per piece should be only one part of the comparison. Evaluate the supplier’s ability to control specifications, verify grade, maintain lot consistency, provide documentation, support corrective action and sustain projected demand.
Use our companion guide, 7 Things to Check in a Neodymium Magnet Supplier, as a supplier-qualification checklist.
Next Steps
Standard part: Search magnet inventory. Custom part: Build a complete magnet RFQ. Several parts or a BOM: Use the Bulk Magnet RFQ. These paths help route the request with the technical and documentation requirements attached from the start.
