Ever ordered magnets only to get something completely different?
Frustrating, right?
Custom neodymium magnets power countless devices today. From medical equipment to car sensors, these powerful magnets make modern tech possible.
But here’s the thing: getting exactly what you need means clear communication.
In our 20+ years with manufacturers, we’ve seen most ordering problems come from incomplete specs. This guide will show you exactly what to include when ordering custom neodymium magnets.
Let’s eliminate the guesswork from your next order.
Table of Contents
Why Proper Specifications Matter
Picture this: Your project’s almost done, but the magnets don’t fit right.
Your deadline looms. The manufacturer says you didn’t specify tolerances.
Sound familiar?
Clear specs aren’t just details—they’re your insurance policy.
They protect your investment and timeline.
When you communicate precisely:
- Manufacturers know exactly what you need
- You get accurate cost estimates the first time
- Production moves forward without delays
- Your final product works as designed
- You avoid returns and reorders
Material Grade and Magnetic Performance
Selecting the Right Grade
Neodymium magnets come in different grades that determine strength. The letter-number combo (like N42 or N52) tells you everything about performance.
“N” stands for neodymium, while the number shows maximum energy. Higher numbers mean stronger pulling force.
Here’s a quick comparison:
- N35: Basic strength, most affordable
- N42: Middle-range strength, good balance of performance and cost
- N48: High-performance for demanding uses
- N52: Ultra-high strength, premium price
Real-world tip:
- Don’t just pick the strongest grade.
- Match it to your needs.
- Sometimes N35 works perfectly and saves money.
Temperature Matters—A Lot
Neodymium magnets lose strength when heated.
Standard N-grade magnets work reliably up to 80°C (176°F).
For higher temperatures, you’ll need special grades:
- M grade: Works up to 100°C (212°F)
- H grade: Works up to 120°C (248°F)
- SH grade: Works up to 150°C (302°F)
- UH grade: Works up to 180°C (356°F)
- EH grade: Works up to 200°C (392°F)
Pro tip:
- Always specify your maximum operating temperature.
- If your application runs hot, a standard N-grade magnet might demagnetize and cause system failure.
Physical Dimensions and Shape
Common and Custom Shapes
The shape you choose affects function, cost, and production time.
Standard shapes include:
- Blocks/rectangles: Versatile for many uses
- Discs/cylinders: Perfect for axial attraction
- Rings: Ideal for focusing magnetic fields
- Arc segments: Used in motors and sensors
- Spheres: Provide all-direction magnetic fields
- Custom polygons: Designed for specific needs
Designer insight:
- Standard shapes cost less and ship faster.
- Custom shapes need special tooling and take longer.
Measurements That Matter
Clear dimensions prevent confusion.
Always use decimal points for precision.
For block magnets, specify:
- Length (L) × Width (W) × Height (H) in mm or inches
- Example: 25.4mm × 12.7mm × 6.35mm (1″ × 0.5″ × 0.25″)
For disc magnets, specify:
- Diameter (D) × Thickness (T)
- Example: 19.05mm × 3.175mm (0.75″ × 0.125″)
For ring magnets, specify:
- Outer Diameter (OD) × Inner Diameter (ID) × Thickness (T)
- Example: 25.4mm × 12.7mm × 6.35mm (1″ × 0.5″ × 0.25″)
Visualization tip: Include a simple diagram with labeled dimensions for complex shapes.
Tolerances That Save Money
Tolerances define acceptable variation.
Tighter tolerances mean higher precision—and higher costs.
Common tolerance ranges:
- Standard precision: ±0.1mm (±0.004″)
- High precision: ±0.05mm (±0.002″)
- Ultra-precision: ±0.02mm (±0.0008″)
Cost-saving advice:
- Only specify tight tolerances for critical dimensions.
- A mixed approach (tight where needed, standard elsewhere) saves money.
Magnetization Direction
Orientation Options
Magnetization direction dramatically affects performance.
Different applications need different orientations.
For block magnets:
- Axial: Magnetized through thickness (poles on largest faces)
- Diametrical: Magnetized through width (poles on side faces)
- Multiple poles: Special arrangements for specific functions
For disc magnets:
- Axial: Poles on flat faces (most common)
- Diametrical: Poles on curved edges (less common)
For ring magnets:
- Axial: Poles on flat faces
- Radial: Poles on inner and outer curved surfaces
- Multi-pole: Alternating poles around circumference
Application example:
- Door catches work best with diametrically magnetized discs.
- For holding applications, axial magnetization gives maximum pull force.
Polarity Marking
In assemblies where north/south orientation matters, request polarity marking.
Common marking methods:
- Colored dots (red for north, blue for south)
- Laser etching (N/S symbols)
- Dimples or physical indicators
- Colored coating on one pole
Assembly tip:
- Clear polarity marking speeds up production and prevents assembly errors.
- Always request it for multi-magnet systems.
Coating and Plating Options
Protection Choices
Raw neodymium corrodes easily. Coatings protect your investment.
Popular coating options:
- Ni-Cu-Ni (nickel-copper-nickel): Triple-layer protection, silver appearance
- Zinc: Budget-friendly protection, blue-silver appearance
- Epoxy: Excellent chemical resistance, customizable colors
- Gold: Premium appearance, good corrosion resistance
- Parylene: Thin, conformal coating for electronic applications
Environmental consideration:
- For outdoor or high-humidity environments, triple-layer Ni-Cu-Ni gives the best protection.
Functional Coatings
Coatings do more than prevent corrosion. They can add functionality.
Special coating considerations:
- Low friction: PTFE coating reduces sliding resistance
- Electrical insulation: Epoxy prevents electrical contact
- Food safety: FDA-approved coatings for food processing equipment
- Medical grade: Biocompatible coatings for healthcare applications
Healthcare example:
- Medical devices often need biocompatible coatings certified for patient contact.
Mechanical and Structural Features
Edge Treatments
Neodymium magnets are brittle. Sharp edges chip easily during handling.
Specify edge treatments:
- Chamfers: Small angled cuts at corners (specify dimensions)
- Radii: Rounded edges (specify radius)
- Tumbling: Mass finishing for slight edge rounding
Handling tip:
- Even small chamfers (0.2-0.5mm) significantly reduce chipping and handling damage.
Holes, Slots, and Features
Custom features transform basic magnets into functional components.
Common customizations:
- Through holes: For mounting screws or bolts
- Countersunk holes: For flush mounting
- Blind holes: Non-penetrating recesses
- Slots: For alignment or weight reduction
- Threads: For direct attachment
Design advice:
- Holes weaken magnetic strength.
- Position them away from critical magnetic circuits when possible.
Magnetic Field Requirements
Pull Force Specifications
For many applications, pull force matters more than grade.
Specify pull force:
- In kilograms (kg) or pounds (lbs)
- Against a standard steel plate
- With specific air gap (if applicable)
Testing standards:
- Request pull testing according to industry standards (ASTM or ISO) for consistent results.
Field Patterns
Advanced applications require specific field patterns.
Specialized magnetization options:
- Multi-pole: Alternating north/south regions
- Halbach arrays: Magnets arranged to focus field on one side
- Radial orientation: For rotary applications
- Chessboard patterns: For specialized sensors
Sensor application:
- Hard drive positioning systems use precisely magnetized arrays to achieve nanometer-level position control.
Order Quantity and Production Planning
Volume Considerations
Production quantity affects both price and manufacturing methods.
Quantity breakpoints typically occur at:
- 100 units
- 500 units
- 1,000 units
- 5,000 units
- 10,000+ units
Budget tip:
- Request pricing at multiple quantity points.
- Sometimes ordering slightly more units significantly cuts per-unit cost.
Prototype vs. Production Specs
Prototypes often differ from production versions.
Common prototype adjustments:
- Using available stock sizes for quick delivery
- Simplified coatings for faster turnaround
- Standard tolerances instead of custom
- Hand-finished features for small quantities
Development advice:
- Clearly state which specifications can be relaxed for prototypes and which are critical even in test versions.
Quality Control and Testing
Certification Requirements
Quality certifications ensure consistency and safety.
Common certifications include:
- ISO 9001: Quality management systems
- RoHS: Restriction of Hazardous Substances
- REACH: Registration, Evaluation, Authorization of Chemicals
- PPAP: Production Part Approval Process (automotive)
Regulatory tip:
- Medical and automotive applications often need full material traceability.
- Specify this upfront.
Inspection Methods
Verification ensures you get what you paid for.
Useful inspection protocols:
- Gauss meter testing: Verifies magnetic field strength
- CMM inspection: Checks dimensional accuracy
- Pull force testing: Confirms actual performance
- Coating thickness testing: Ensures proper protection
- Salt spray testing: Validates corrosion resistance
Quality recommendation:
- Specify acceptable quality level (AQL) for statistical sampling.
- AQL 2.5 is standard for most applications.
Environmental and Safety Considerations
Operating Conditions
Where and how magnets will be used affects design decisions.
Important environmental factors:
- Temperature range: Both maximum and minimum
- Humidity level: Moisture exposure frequency
- Chemical exposure: Cleaning agents, process chemicals
- Vibration: Mechanical stress during operation
- UV exposure: Outdoor applications
- Vacuum applications: Special considerations for outgassing
Aerospace example:
- Space applications need magnets that perform in vacuum and extreme temperature cycles without outgassing.
Safety Planning
Neodymium magnets pose unique handling challenges.
Safety considerations:
- Brittle nature: Can chip or shatter if dropped
- Powerful attraction: Pinch hazards during assembly
- Magnetic fields: Potential interference with electronics
- Shipping regulations: Special packaging for air freight
Factory tip:
- For high-volume assembly, request safety handling instructions and training recommendations.
Putting It All Together: Sample Specification
Here’s a comprehensive example that brings all elements together:
Custom Neodymium Magnet Specification
1. Material Grade and Performance:
- Grade: N42SH (high temperature grade)
- Maximum operating temperature: 150°C
2. Physical Dimensions:
- Shape: Block/rectangular
- Dimensions: 30mm × 10mm × 5mm
- Tolerances: ±0.1mm on all dimensions
3. Magnetization:
- Direction: Through 5mm thickness
- Polarity: North pole to be marked with red dot
4. Coating:
- Type: Ni-Cu-Ni triple layer
- Thickness: Standard (12-25μm)
5. Mechanical Features:
- All edges to have 0.3mm × 45° chamfer
- 3mm diameter through-hole centered on one 10mm × 5mm face
6. Magnetic Requirements:
- Minimum pull force: 5.2kg on 10mm steel plate
- Field uniformity: ±5% across main poles
7. Order Information:
- Quantity: 1,000 units initial order
- Expected annual usage: 4,000-5,000 units
8. Quality and Inspection:
- Certification: ISO 9001, RoHS compliance
- Testing: 100% visual inspection, 10% pull force verification
- Packaging: 50 pieces per inner box with separators
9. Environmental Factors:
- Indoor use, occasional cleaning with isopropyl alcohol
- Mechanical shock resistance required for automated handling
Getting It Right the First Time
Clear specs create success.
The effort pays off in better products and fewer headaches.
Remember these key points:
- Focus on critical requirements
- Provide measurable parameters
- Consider the magnet’s entire lifecycle
- Work with your supplier as a partner
- Save successful specs for future orders
Need help with specific requirements?
Our engineering team offers free consultations.
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