Ring NdFeB Magnets

Description

Product Overview

Ring NdFeB magnets, also known as neodymium ring magnets or annular magnets, are high-performance rare earth permanent magnets with a central hole. They combine the high energy density of sintered neodymium-iron-boron material with a practical geometry that is easy to mount on shafts, screws, pins, sensors and rotating assemblies.

Ningbo Vanguard Technologies supplies ring magnets across the full grade family — from standard N-grade through M, H, SH, UH, and EH high-temperature series — enabling precise performance matching for motors, sensors, magnetic couplings, holding systems and compact mechanical assemblies.

Whether you need a standard catalogue ring, a countersunk ring magnet, or a fully customized annular magnet with special magnetization, Vanguard can provide sample shipment within 10–15 days and mass-production support with magnetic testing, dimensional inspection and coating verification.

Quick View

Ring NdFeB Magnet Selection Snapshot

N35-N55

Available Grade Range

From high Br standard grades to high-temperature motor and coupling grades.

80-200 °C

Working Temperature Range

N, M, H, SH, UH and EH series can be selected by thermal requirement.

ID / OD

Key Geometry Control

Inner diameter, outer diameter, thickness, chamfer and countersink can be customized.

10-15 Days

Prototype Sample Lead Time

Fast sampling after drawing, grade, coating and magnetization confirmation.

Temperature Grade Guide

N Series

80 °C

M Series

100 °C

H Series

120 °C

SH Series

150 °C

UH / EH

180-200 °C

Application Demand Focus

Motor Rotors

Alignment

Sensors

Polarity

Couplings

Torque

Audio

Flux

Holding

Mounting

1Drawing ReviewOD, ID, thickness, chamfer

2Grade MatchBr, Hcj, temperature margin

3Coating PlanNiCuNi, epoxy, Zn, custom

4MagnetizationAxial, radial, diametrical, multi-pole

5InspectionFlux, size, coating, polarity

Industries Served

Key Applications

Motor Rotors

Axially or radially magnetized ring magnets for BLDC motors, servo motors and compact rotor assemblies requiring stable flux output and accurate shaft alignment.

Magnetic Sensors

Precision rings for Hall sensors, rotary encoders, speed sensors and position-detection modules where controlled polarity and repeatable magnetic signal are required.

Magnetic Couplings

Ring magnets for non-contact torque transfer, pumps, mixers and sealed drive systems where magnetic coupling helps isolate liquid, dust or corrosive environments.

Speakers & Audio

High-flux annular magnets for speakers, receivers, microphones and acoustic modules needing compact size, strong magnetic field and consistent batch performance.

Holding Assemblies

Countersunk and through-hole ring magnets for magnetic mounts, fixtures, tools, cabinet hardware and removable holding systems.

Medical & Instruments

Custom annular magnets for precision instruments, medical device actuators and laboratory equipment requiring clean surfaces and tight dimensional control.

Magnetic Performance

Grade & Magnetic Properties

Standard grades for ring NdFeB magnets. All values at 20 °C. Values are typical; exact grade selection is confirmed per application.

Grade	Remanence		Coercivity		Intrinsic Coercivity		Max. Energy Product		Temp. Coefficient (α)		Max. Working Temperature °C (L/D=0.7)
	Br		Hcb		Hcj		(BH)max		αBr (%/°C)	αHcj (%/°C)
	T	kGs	kA/m	kOe	kA/m	kOe	kJ/m³	MGOe	αBr (%/°C)	αHcj (%/°C)
N30	1.08–1.13	10.8–11.3	≥798	≥10.0	≥955	≥12	223–247	28–31	−0.12	−0.76	80
N33	1.13–1.17	11.3–11.7	≥836	≥10.5	≥955	≥12	247–271	31–34	−0.12	−0.76	80
N35	1.17–1.22	11.7–12.2	≥868	≥10.9	≥955	≥12	263–287	33–36	−0.12	−0.76	80
N38	1.22–1.25	12.2–12.5	≥899	≥11.3	≥955	≥12	287–310	36–39	−0.12	−0.76	80
N40	1.25–1.28	12.5–12.8	≥907	≥11.4	≥955	≥12	302–326	38–41	−0.12	−0.76	80
N42	1.28–1.32	12.8–13.2	≥915	≥11.5	≥955	≥12	318–342	40–43	−0.12	−0.76	80
N45	1.32–1.38	13.2–13.8	≥923	≥11.6	≥955	≥12	342–366	43–46	−0.12	−0.76	80
N48	1.38–1.42	13.8–14.2	≥923	≥11.6	≥955	≥12	366–390	46–49	−0.12	−0.76	80
N50	1.40–1.45	14.0–14.5	≥796	≥10.0	≥876	≥11	382–406	48–51	−0.12	−0.76	80
N52	1.43–1.48	14.3–14.8	≥796	≥10.0	≥876	≥11	398–422	50–53	−0.12	−0.76	80
N55	1.46–1.52	14.6–15.2	≥796	≥10.0	≥876	≥11	414–430	52–54	−0.12	−0.76	80
N35M	1.17–1.22	11.7–12.2	≥868	≥10.9	≥1114	≥14	263–287	33–36	−0.12	−0.68	100
N38M	1.22–1.25	12.2–12.5	≥899	≥11.3	≥1114	≥14	287–310	36–39	−0.12	−0.68	100
N40M	1.25–1.28	12.5–12.8	≥923	≥11.6	≥1114	≥14	302–326	38–41	−0.12	−0.68	100
N42M	1.28–1.32	12.8–13.2	≥955	≥12.0	≥1114	≥14	318–342	40–43	−0.12	−0.68	100
N45M	1.32–1.38	13.2–13.8	≥995	≥12.5	≥1114	≥14	342–366	43–46	−0.12	−0.68	100
N48M	1.37–1.43	13.7–14.3	≥1027	≥12.9	≥1114	≥14	366–390	46–49	−0.12	−0.68	100
N50M	1.40–1.45	14.0–14.5	≥1033	≥13.0	≥1114	≥14	382–406	48–51	−0.12	−0.68	100
N52M	1.43–1.48	14.3–14.8	≥1050	≥13.2	≥1114	≥14	398–422	50–53	−0.12	−0.68	100
N54M	1.45–1.50	14.5–15.0	≥1051	≥13.2	≥1114	≥14	414–438	52–55	−0.12	−0.68	100
N35H	1.17–1.22	11.7–12.2	≥868	≥10.9	≥1353	≥17	263–287	33–36	−0.12	−0.66	120
N38H	1.22–1.25	12.2–12.5	≥899	≥11.3	≥1353	≥17	287–310	36–39	−0.12	−0.66	120
N40H	1.25–1.28	12.5–12.8	≥923	≥11.6	≥1353	≥17	302–326	38–41	−0.12	−0.66	120
N42H	1.28–1.32	12.8–13.2	≥955	≥12.0	≥1353	≥17	318–342	40–43	−0.12	−0.66	120
N45H	1.32–1.36	13.2–13.6	≥963	≥12.1	≥1353	≥17	342–366	43–46	−0.12	−0.66	120
N48H	1.37–1.43	13.7–14.3	≥995	≥12.5	≥1353	≥17	366–390	46–49	−0.12	−0.66	120
N50H	1.40–1.45	14.0–14.5	≥1011	≥12.7	≥1353	≥17	382–406	48–51	−0.12	−0.66	120
N52H	1.43–1.48	14.3–14.8	≥1027	≥12.9	≥1353	≥17	398–422	50–53	−0.12	−0.66	120
N35SH	1.17–1.22	11.7–12.2	≥876	≥11.0	≥1592	≥20	263–287	33–36	−0.11	−0.56	150
N38SH	1.22–1.25	12.2–12.5	≥907	≥11.4	≥1592	≥20	287–310	36–39	−0.11	−0.56	150
N40SH	1.25–1.28	12.5–12.8	≥939	≥11.8	≥1592	≥20	302–326	38–41	−0.11	−0.56	150
N42SH	1.28–1.32	12.8–13.2	≥987	≥12.4	≥1592	≥20	318–342	40–43	−0.11	−0.56	150
N45SH	1.32–1.38	13.2–13.8	≥1003	≥12.6	≥1592	≥20	342–366	43–46	−0.11	−0.56	150
N48SH	1.37–1.43	13.7–14.3	≥1027	≥12.9	≥1592	≥20	366–390	46–49	−0.11	−0.56	150
N50SH	1.40–1.45	14.0–14.5	≥1003	≥12.6	≥1592	≥20	382–406	48–51	−0.11	−0.56	150
N30UH	1.08–1.13	10.8–11.3	≥812	≥10.2	≥1990	≥25	223–247	28–31	−0.10	−0.50	180
N33UH	1.13–1.17	11.3–11.7	≥852	≥10.7	≥1990	≥25	247–271	31–34	−0.10	−0.50	180
N35UH	1.17–1.22	11.7–12.2	≥860	≥10.8	≥1990	≥25	263–287	33–36	−0.10	−0.50	180
N38UH	1.22–1.25	12.2–12.5	≥876	≥11.0	≥1990	≥25	287–310	36–39	−0.10	−0.50	180
N40UH	1.25–1.28	12.5–12.8	≥899	≥11.3	≥1990	≥25	302–326	38–41	−0.10	−0.50	180
N42UH	1.28–1.32	12.8–13.2	≥899	≥11.3	≥1990	≥25	318–342	40–43	−0.10	−0.50	180
N45UH	1.32–1.36	13.2–13.6	≥908	≥11.4	≥1990	≥25	342–366	43–46	−0.10	−0.50	180
N48UH	1.37–1.43	13.7–14.3	≥908	≥11.4	≥1990	≥25	366–390	46–49	−0.10	−0.50	180
N28EH	1.04–1.08	10.4–10.8	≥780	≥9.8	≥2388	≥30	207–231	26–29	−0.10	−0.45	200
N30EH	1.08–1.13	10.8–11.3	≥812	≥10.2	≥2388	≥30	223–247	28–31	−0.10	−0.45	200
N33EH	1.13–1.17	11.3–11.7	≥836	≥10.5	≥2388	≥30	247–271	31–34	−0.10	−0.45	200
N35EH	1.17–1.22	11.7–12.2	≥876	≥11.0	≥2388	≥30	263–287	33–36	−0.10	−0.45	200
N38EH	1.22–1.25	12.2–12.5	≥899	≥11.3	≥2388	≥30	287–310	36–39	−0.10	−0.45	200
N40EH	1.25–1.28	12.5–12.8	≥899	≥11.3	≥2388	≥30	302–326	38–41	−0.10	−0.45	200
N42EH	1.28–1.32	12.8–13.2	≥899	≥11.3	≥2388	≥30	318–342	40–43	−0.10	−0.45	200
N45EH	1.32–1.36	13.2–13.6	≥899	≥11.3	≥2388	≥30	342–366	43–46	−0.10	−0.45	200
N28AH	1.04–1.08	10.4–10.8	≥787	≥9.9	≥2786	≥35	207–231	26–29	−0.10	−0.45	230
N30AH	1.08–1.13	10.8–11.3	≥819	≥10.3	≥2786	≥35	223–247	28–31	−0.10	−0.45	230
N33AH	1.13–1.17	11.3–11.7	≥843	≥10.6	≥2786	≥35	247–271	31–34	−0.10	−0.45	230
N35AH	1.17–1.22	11.7–12.2	≥876	≥11.0	≥2786	≥35	263–287	33–36	−0.10	−0.45	230
N38AH	1.22–1.25	12.2–12.5	≥899	≥11.3	≥2786	≥35	287–310	36–39	−0.10	−0.45	230

Typical Physical Properties (All Sintered NdFeB Grades)

Parameter	Unit	Reference Value	Parameter	Unit	Reference Value
Curie Temperature	°C	310 ~ 400	Thermal Conductivity	W/m·°C	8 ~ 10
Density	g/cm³	7.4 ~ 7.7	Young's Modulus	GPa	150 ~ 200
Vickers Hardness	HV	500 ~ 700	Electrical Resistivity (C∥)	μΩ·m	1.4 ~ 1.6
Recoil Permeability	—	1.02 ~ 1.08	Electrical Resistivity (C⊥)	μΩ·m	1.2 ~ 1.4
Compressive Strength	MPa	1000 ~ 1100	Coeff. of Thermal Expansion (C∥)	10⁻⁶/°C	4 ~ 9
Flexural Strength	MPa	150 ~ 400	Coeff. of Thermal Expansion (C⊥)	10⁻⁶/°C	−2 ~ 0

Magnetization Orientations Available

Surface Treatment

Coating & Plating Options

NdFeB is susceptible to oxidation without adequate surface protection. Ring magnets can be supplied with standard or enhanced coatings according to humidity, salt spray, bonding method and working temperature.

Ni·Cu·Ni

Industry standard with bright metallic finish.

10-20 μm · Bright Silver

General applications, speakers, sensors and clean indoor use.

Zinc (Zn)

Cost-effective corrosion protection.

5-10 μm · Blue-white / Dark Silver

Industrial holding magnets, fixtures and general assemblies.

Epoxy

Improved humidity and chemical resistance.

Moisture Preferred

10-20 μm · Black / Grey

Humid environments, bonding surfaces and protected outdoor use.

NiCuNi + Epoxy

Enhanced multi-layer protection.

12-25 μm · Matt Black

High-humidity, aggressive environments and demanding industrial assemblies.

Geometry & Tolerances

Dimension Capability

Ring magnets are defined by outer diameter (OD), inner diameter (ID), and thickness / axial length (T). Standard tolerance is ± 0.05 mm; tight-tolerance ± 0.03 mm, countersunk holes, stepped holes and special polarity marking are available on request.

Dimension	Minimum	Maximum	Standard Tol.
Outer Diameter (OD)	2 mm	200 mm	± 0.05 mm
Inner Diameter (ID)	0.5 mm	180 mm	± 0.05 mm
Thickness / Length (T)	0.5 mm	100 mm	± 0.05 mm
Concentricity	By drawing	By drawing	Customized

Engineering Selection

How to Specify Ring NdFeB Magnets

Ring magnets should be specified together with the assembly method and magnetic circuit. Vanguard reviews OD, ID, thickness, L/D ratio, hole tolerance, magnetization direction, working temperature, coating and installation stress before confirming production details.

Hole and mounting fit: ID tolerance, concentricity, countersink angle and screw clearance should be confirmed early when the ring is mounted on shafts, pins or fasteners.

Magnetization direction: Axial magnetization is standard for holding and speaker rings; diametrical, radial or multi-pole magnetization is recommended for encoders, sensors and magnetic couplings.

Mechanical reliability: Because ring magnets are brittle, chamfer, edge radius, coating thickness and installation force should be controlled to reduce cracking or coating damage.

Custom Capability

Available Custom Features

Item	Options	Typical Purpose
Geometry	Flat ring, tube, countersunk ring, stepped ring, segmented ring	Fit shafts, screws, rotors, speakers, sensors and magnetic holders.
Magnetization	Axial, diametrical, radial, multi-pole, paired polarity	Support encoders, couplings, motors, speaker systems and holding assemblies.
Edge Treatment	Chamfer, radius, deburring, polished surface	Reduce chipping during insertion, screw mounting and automated handling.
Polarity Marking	Dot mark, line mark, laser mark, matched-set packing	Improve assembly accuracy and reduce polarity mistakes in production.

Manufacturing Process

From Powder to Finished Ring Magnet

Production starts with rare-earth alloy preparation, hydrogen decrepitation, jet milling and magnetic-field alignment. The sintered blanks are aged, sliced, drilled or core-ground, then finished to final OD, ID and thickness before coating, magnetization and inspection.

For automated assembly, Vanguard can provide matched magnetic batches, polarity marking, anti-chip packing and inspection data for hole tolerance, concentricity, surface flux and coating thickness.

Quality Assurance

Inspection & Validation

Magnetic testing: Br, Hcb, Hcj, (BH)max, surface flux, flux linkage, polarity and magnetization direction verification.

Dimensional control: OD, ID, thickness, concentricity, flatness, chamfer, countersink angle and appearance inspection.

Coating verification: Thickness, adhesion, salt spray, humidity resistance and thermal shock testing according to coating type.

Documentation: Material certificate, inspection report, RoHS/REACH declaration and lot traceability records are available for shipment release.

Request a Quote

Information Needed for Fast Quotation

To speed up engineering review, please send a 2D/3D drawing or list the key specifications below. If your project is still in design stage, Vanguard can help compare grade, coating and magnetization options before tooling.

Outer diameter, inner diameter, thickness, tolerance, chamfer and concentricity
Flat ring, tube, countersunk ring, stepped ring or segmented ring requirement
Material grade or target Br/Hcj, plus maximum working temperature
Magnetization direction, polarity marking and required surface flux if available
Coating type, salt-spray requirement, adhesive process and operating environment
Sample quantity, annual volume, packing requirement and target delivery schedule

Support

Frequently Asked Questions

What is the difference between axial, diametrical and radial ring magnetization?

Axial magnetization places the north and south poles on the two flat faces and is common for holding and speaker rings. Diametrical magnetization places poles across the diameter and is often used for sensors and encoders. Radial or multi-pole magnetization is used for couplings, motors and special rotating magnetic fields.

Can you produce countersunk ring magnets?

Yes. Countersunk, stepped-hole and straight-hole ring magnets can be customized. Please provide screw size, countersink angle, hole tolerance and the mounting direction so the polarity and coating can be confirmed correctly.

How do I choose the right grade for ring magnets?

Grade selection depends on working temperature, ring geometry, magnetic circuit and demagnetization risk. N-grade is suitable for room-temperature holding, while M/H/SH/UH/EH grades are recommended for motors, couplings and high-temperature assemblies.

Do you provide inspection reports?

Yes. Material certificate, magnetic test data, dimensional report, coating thickness, salt-spray data, RoHS/REACH declaration and lot traceability records are available according to project requirements.

What is the lead time for custom ring NdFeB magnets?

Prototype samples are typically 10-15 working days after drawing approval. Mass-production orders are usually 25-35 working days depending on grade, coating, magnetization, quantity and inspection requirements.

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Ring NdFeB Magnets

Description

Ring NdFeB Magnets

Ring NdFeB Magnet Selection Snapshot

Key Applications

Grade & Magnetic Properties

Coating & Plating Options

Dimension Capability

How to Specify Ring NdFeB Magnets

Available Custom Features

From Powder to Finished Ring Magnet

Inspection & Validation

Information Needed for Fast Quotation

Frequently Asked Questions

Get in Touch with Us

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