Product available Ships tomorrow

MP 30x7/3x3 / N38 - ring magnet

Name: Dhit sp. z o.o.
Address: Kościuszki 6A, Ożarów Mazowiecki, Poland, 05-850, PL
Telephone: +48 22 499 98 98
Price range: 1-6500
Rating: 5

ring magnet

Catalog no 030250

GTIN: 5906301812265

5.00

Diameter

30 mm [±0,1 mm]

internal diameter Ø

7/3 mm [±0,1 mm]

Height

3 mm [±0,1 mm]

Weight

15.75 g

Magnetization Direction

↑ axial

Load capacity

3.64 kg / 35.69 N

Magnetic Induction

121.58 mT / 1216 Gs

Coating

[NiCuNi] Nickel

6.84 ZŁ with VAT / pcs + price for transport

5.56 ZŁ net + 23% VAT / pcs

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MP 30x7/3x3 / N38 - ring magnet

Specification / characteristics MP 30x7/3x3 / N38 - ring magnet

properties

properties	values
Cat. no.	030250
GTIN	5906301812265
Production/Distribution	Dhit sp. z o.o. ul. Zielona 14 05-850 Ożarów Mazowiecki PL
Country of origin	Poland / China / Germany
Customs code	85059029
Diameter	30 mm [±0,1 mm]
internal diameter Ø	7/3 mm [±0,1 mm]
Height	3 mm [±0,1 mm]
Weight	15.75 g
Magnetization Direction	↑ axial
Load capacity ~ ?	3.64 kg / 35.69 N
Magnetic Induction ~ ?	121.58 mT / 1216 Gs
Coating	[NiCuNi] Nickel
Manufacturing Tolerance	±0.1 mm

Magnetic properties of material N38

Specification / characteristics MP 30x7/3x3 / N38 - ring magnet

properties	values	units
remenance Br [Min. - Max.] ?	12.2-12.6	kGs
remenance Br [Min. - Max.] ?	1220-1260	T
coercivity bHc ?	10.8-11.5	kOe
coercivity bHc ?	860-915	kA/m
actual internal force iHc	≥ 12	kOe
actual internal force iHc	≥ 955	kA/m
energy density [Min. - Max.] ?	36-38	BH max MGOe
energy density [Min. - Max.] ?	287-303	BH max KJ/m
max. temperature ?	≤ 80	°C

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C

properties	values	units
Vickers hardness	≥550	Hv
Density	≥7.4	g/cm³
Curie Temperature TC	312 - 380	°C
Curie Temperature TF	593 - 716	°F
Specific resistance	150	μΩ⋅Cm
Bending strength	250	Mpa
Compressive strength	1000~1100	Mpa
Thermal expansion parallel (∥) to orientation (M)	(3-4) x 106	°C^-1
Thermal expansion perpendicular (⊥) to orientation (M)	-(1-3) x 10-6	°C^-1
Young's modulus	1.7 x 104	kg/mm²

Physical simulation of the product - technical parameters

Presented values constitute the outcome of a engineering calculation. Values rely on algorithms for the class NdFeB. Actual performance might slightly differ from theoretical values. Use these data as a supplementary guide when designing systems.

Table 1: Static force (force vs gap) - characteristics
MP 30x7/3x3 / N38

Distance (mm)	Induction (Gauss) / mT	Pull Force (kg)	Risk Status
0 mm	1039 Gs 103.9 mT	3.64 kg / 3640.0 g 35.7 N	warning
1 mm	1015 Gs 101.5 mT	3.48 kg / 3477.6 g 34.1 N	warning
2 mm	980 Gs 98.0 mT	3.24 kg / 3240.7 g 31.8 N	warning
3 mm	936 Gs 93.6 mT	2.95 kg / 2951.6 g 29.0 N	warning
5 mm	827 Gs 82.7 mT	2.31 kg / 2305.8 g 22.6 N	warning
10 mm	539 Gs 53.9 mT	0.98 kg / 981.0 g 9.6 N	safe
15 mm	329 Gs 32.9 mT	0.37 kg / 365.1 g 3.6 N	safe
20 mm	202 Gs 20.2 mT	0.14 kg / 137.9 g 1.4 N	safe
30 mm	85 Gs 8.5 mT	0.02 kg / 24.6 g 0.2 N	safe
50 mm	23 Gs 2.3 mT	0.00 kg / 1.8 g 0.0 N	safe

Magnetic force drops sharply with every subsequent millimeter of distance. Note that even the smallest gap (e.g., contamination, varnish, dust) significantly diminishes the holding power. Magnetic products hold most effectively at the point of direct contact; distance weakens the power. Observe how rapidly the parameters drop, when the product does not adhere tightly to the steel surface. When designing the mounting, discard redundant distances.

Table 2: Sliding Force (Vertical Surface)
MP 30x7/3x3 / N38

Distance (mm)	Friction coefficient	Pull Force (kg)
0 mm	Stal (~0.2)	0.73 kg / 728.0 g 7.1 N
1 mm	Stal (~0.2)	0.70 kg / 696.0 g 6.8 N
2 mm	Stal (~0.2)	0.65 kg / 648.0 g 6.4 N
3 mm	Stal (~0.2)	0.59 kg / 590.0 g 5.8 N
5 mm	Stal (~0.2)	0.46 kg / 462.0 g 4.5 N
10 mm	Stal (~0.2)	0.20 kg / 196.0 g 1.9 N
15 mm	Stal (~0.2)	0.07 kg / 74.0 g 0.7 N
20 mm	Stal (~0.2)	0.03 kg / 28.0 g 0.3 N
30 mm	Stal (~0.2)	0.00 kg / 4.0 g 0.0 N
50 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N

The following data shows the approximate shear load sufficient to initiate the shifting of the magnet down against a upright steel plate (considering typical friction coefficient). This value depends on the gap size between the magnet and the surface.

Table 3: Wall mounting (shearing) - vertical pull
MP 30x7/3x3 / N38

Surface type	Friction coefficient / % Mocy	Max load (kg)
Raw steel	µ = 0.3 30% Nominalnej Siły	1.09 kg / 1092.0 g 10.7 N
Painted steel (standard)	µ = 0.2 20% Nominalnej Siły	0.73 kg / 728.0 g 7.1 N
Oily/slippery steel	µ = 0.1 10% Nominalnej Siły	0.36 kg / 364.0 g 3.6 N
Magnet with anti-slip rubber	µ = 0.5 50% Nominalnej Siły	1.82 kg / 1820.0 g 17.9 N

When hanging a magnet on a upright plane (e.g., a board), it will only hold barely about 20%-30% of nominal attraction strength. Gravitational force and a low friction coefficient cause that products move down easier than they detach. Designing a wall mount? Consider that the shear force is noticeably lower than the perpendicular breakaway force. On a smooth steel, the magnet will give way down under a significantly smaller weight. Application of an anti-slip pad can effectively increase the grip.

Table 4: Material efficiency (saturation) - power losses
MP 30x7/3x3 / N38

Steel thickness (mm)	% power	Real pull force (kg)
0.5 mm	10%	0.36 kg / 364.0 g 3.6 N
1 mm	25%	0.91 kg / 910.0 g 8.9 N
2 mm	50%	1.82 kg / 1820.0 g 17.9 N
5 mm	100%	3.64 kg / 3640.0 g 35.7 N
10 mm	100%	3.64 kg / 3640.0 g 35.7 N

A thin metal plate is incapable of conduct the entire magnetic field, which weakens actual performance of the magnet. Should you mount a strong magnet to a weak sheet, the field will penetrate right through and the pull force will drop sharply. To utilize 100% of this neodymium's power, you require a sufficiently solid piece of steel. The saturation effect means that on sheet metal structures (e.g., thin profiles), the product holds weaker. We recommend selecting the steel dimension from these parameters.

Table 5: Thermal resistance (material behavior) - thermal limit
MP 30x7/3x3 / N38

Ambient temp. (°C)	Power loss	Remaining pull	Status
20 °C	0.0%	3.64 kg / 3640.0 g 35.7 N	OK
40 °C	-2.2%	3.56 kg / 3559.9 g 34.9 N	OK
60 °C	-4.4%	3.48 kg / 3479.8 g 34.1 N
80 °C	-6.6%	3.40 kg / 3399.8 g 33.4 N
100 °C	-28.8%	2.59 kg / 2591.7 g 25.4 N

Classic neodymiums lose power past the thermal threshold. Watch out for overheating – excessive heat can permanently damage this product. With increasing heat, the magnet's force temporarily decreases. Refrain from using this magnet near heat sources higher than its operating temperature limit. Too high temperature will result in permanent loss of magnetism.

*Important note: Temperature resistance is determined by both grade, as well as the dimension ratios. Flat magnets (low permeance coefficient) are more susceptible to demagnetization under lower heat stress compared to rod magnets. Warning indicator in the table indicates a risk of irreversible loss for this specific geometry.

Table 6: Two magnets (repulsion) - forces in the system
MP 30x7/3x3 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	3.96 kg / 3958 g 38.8 N 1 995 Gs	N/A
1 mm	3.88 kg / 3882 g 38.1 N 2 058 Gs	3.49 kg / 3493 g 34.3 N ~0 Gs
2 mm	3.78 kg / 3781 g 37.1 N 2 031 Gs	3.40 kg / 3403 g 33.4 N ~0 Gs
3 mm	3.66 kg / 3661 g 35.9 N 1 998 Gs	3.30 kg / 3295 g 32.3 N ~0 Gs
5 mm	3.37 kg / 3372 g 33.1 N 1 918 Gs	3.04 kg / 3035 g 29.8 N ~0 Gs
10 mm	2.51 kg / 2507 g 24.6 N 1 654 Gs	2.26 kg / 2257 g 22.1 N ~0 Gs
20 mm	1.07 kg / 1067 g 10.5 N 1 079 Gs	0.96 kg / 960 g 9.4 N ~0 Gs
50 mm	0.06 kg / 61 g 0.6 N 258 Gs	0.05 kg / 55 g 0.5 N ~0 Gs

Two magnets interact from a significantly greater distance than a neodymium and metal setup. The setup of two magnets generates a stronger field and a wider radius of performance. Planning to create a powerful holder? Use a pair of magnets instead of one magnet and a steel. Exercise caution that when bringing together two magnets, the pinch force is huge. The levitation is marginally weaker than the attraction, but still significant.
*The magnetic induction for N-N configuration is approximately ~0 Gs at the midpoint between the magnets (due to field cancellation).

Table 7: Hazards (electronics) - warnings
MP 30x7/3x3 / N38

Object / Device	Limit (Gauss) / mT	Safe distance
Pacemaker	5 Gs (0.5 mT)	9.0 cm
Hearing aid	10 Gs (1.0 mT)	7.0 cm
Mechanical watch	20 Gs (2.0 mT)	5.5 cm
Phone / Smartphone	40 Gs (4.0 mT)	4.5 cm
Remote	50 Gs (5.0 mT)	4.0 cm
Payment card	400 Gs (40.0 mT)	1.5 cm
HDD hard drive	600 Gs (60.0 mT)	1.0 cm

Powerful magnet radiation poses a real danger to IT equipment and pacemakers. These NdFeB products generate a field that prevents correct functioning of sensitive medical devices. Notice: the unseen radiation penetrates the body and glass. Special caution must be taken by people with cochlear implants and drug dispensers. Influence will be felt by: automatic timepieces, car keys, membranes, and screens. Do not place the magnet near cards, hard drives, or precise measuring instruments.

Table 8: Impact energy (cracking risk) - collision effects
MP 30x7/3x3 / N38

Start from (mm)	Speed (km/h)	Energy (J)
10 mm	17.73 km/h (4.92 m/s)	0.19 J
30 mm	26.67 km/h (7.41 m/s)	0.43 J
50 mm	34.29 km/h (9.53 m/s)	0.71 J
100 mm	48.48 km/h (13.47 m/s)	1.43 J

Magnetic elements are very brittle – a violent impact against metal risks their cracking. Watch the impact speed – a magnet released freely speeds with massive force. Impact energy can cause material chips or dangerous crushing to fingers. Be sure to control the product during installation so it doesn't hit with great force against the steel surface. A collision at high speed means shattering of the magnet. Wear eye protection when playing with large magnets.

Table 9: Coating parameters (durability)
MP 30x7/3x3 / N38

Technical parameter	Value / Description
Coating type	[NiCuNi] Nickel
Layer structure	Nickel - Copper - Nickel
Layer thickness	10-20 µm
Salt spray test (SST) ?	24 h
Recommended environment	Indoors only (dry)

The SST (salt spray test) is an industry standard for determining coating lifespan in harsh conditions. Moisture resistance is crucial for installations in bathrooms or outdoors.

Table 10: Electrical data (Flux)
MP 30x7/3x3 / N38

Parameter	Value	Jedn. SI / Opis
Strumień (Flux)	8 395 Mx	84.0 µWb
Współczynnik Pc	0.13	Niski (Płaski)

Flux value flowing through the pole face. Essential parameter for motor design and Hall effect devices. Pc Factor determines the working geometry.

Table 11: Physics of underwater searching
MP 30x7/3x3 / N38

Environment	Effective steel pull	Effect
Air (land)	3.64 kg	Standard
Water (riverbed)	4.17 kg (+0.53 kg Buoyancy gain)	+14.5%

Warning: This magnet has a standard nickel coating. After use in water, it must be dried and maintained immediately, otherwise it will rust!

Water displaces steel, making heavy objects slightly lighter. However, remember the water resistance when pulling the rope quickly.

1. Montaż na Ścianie (Ześlizg)

*Uwaga: Na pionowej ścianie magnes utrzyma tylko ok. 20-30% tego co na suficie.

2. Wpływ Grubości Blachy

*Cienka blacha (np. obudowa PC 0.5mm) drastycznie osłabia magnes.

3. Wytrzymałość Temperaturowa

*Dla materiału N38 granica bezpieczeństwa to 80°C.

Magnet Unit Converter

Magnet Pull Force

Force (N)

Force in lbs

Magnetic Field

Induction (Gs)

Tesla (T)

Insert your figure into any field, and the rest convert automatically.

Jak rozdzielać?

Nie próbuj odrywać magnesów siłą!
Zawsze zsuwaj je na bok krawędzi stołu.

STAY

MOVE

Zasady Bezpieczeństwa

Elektronika

Trzymaj z dala od dysków HDD, kart płatniczych i telefonów.

Rozruszniki Serca

Osoby z rozrusznikiem muszą zachować dystans min. 10 cm.

Nie dla dzieci

Ryzyko połknięcia. Połknięcie dwóch magnesów grozi śmiercią.

Kruchy materiał

Magnes to ceramika! Uderzenie o inny magnes spowoduje odpryski.

Do czego użyć tego magnesu?

Sprawdzone zastosowania dla wymiaru 15x10x2 mm

Elektronika i Czujniki

Idealny jako element wyzwalający dla czujników Halla oraz kontaktronów w systemach alarmowych. Płaski kształt (2mm) pozwala na ukrycie go w wąskich szczelinach obudowy.

Modelarstwo i Druk 3D

Stosowany do tworzenia niewidocznych zamknięć w modelach drukowanych 3D. Można go wprasować w wydruk lub wkleić w kieszeń zaprojektowaną w modelu CAD.

Meble i Fronty

Używany jako "domykacz" lekkich drzwiczek szafkowych, gdzie standardowe magnesy meblowe są za grube. Wymaga wklejenia w płytkie podfrezowanie.

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It is ideally suited for places where solid attachment of the magnet to the substrate is required without the risk of detachment. Mounting is clean and reversible, unlike gluing. It is also often used in advertising for fixing signs and in workshops for organizing tools.

This material behaves more like porcelain than steel, so it doesn't forgive mistakes during mounting. When tightening the screw, you must maintain great sensitivity. We recommend tightening manually with a screwdriver, not an impact driver, because excessive force will cause the ring to crack. The flat screw head should evenly press the magnet. Remember: cracking during assembly results from material properties, not a product defect.

These magnets are coated with standard Ni-Cu-Ni plating, which protects them in indoor conditions, but is not sufficient for rain. Damage to the protective layer during assembly is the most common cause of rusting. If you must use it outside, paint it with anti-corrosion paint after mounting.

The inner hole diameter determines the maximum size of the mounting element. If the magnet does not have a chamfer (cone), we recommend using a screw with a flat or cylindrical head, or possibly using a washer. Aesthetic mounting requires selecting the appropriate head size.

It is a magnetic ring with a diameter of 30 mm and thickness 3 mm. The key parameter here is the lifting capacity amounting to approximately 3.64 kg (force ~35.69 N). The mounting hole diameter is precisely 7/3 mm.

These magnets are magnetized axially (through the thickness), which means one flat side is the N pole and the other is S. In the case of connecting two rings, make sure one is turned the right way. We do not offer paired sets with marked poles in this category, but they are easy to match manually.

Pros and cons of rare earth magnets.

Besides their exceptional field intensity, neodymium magnets offer the following advantages:

They retain full power for almost ten years – the drop is just ~1% (in theory),
They retain their magnetic properties even under external field action,
A magnet with a shiny silver surface looks better,
Magnetic induction on the top side of the magnet remains impressive,
Neodymium magnets are characterized by very high magnetic induction on the magnet surface and can work (depending on the form) even at a temperature of 230°C or more...
Considering the possibility of flexible shaping and adaptation to custom requirements, NdFeB magnets can be manufactured in a broad palette of geometric configurations, which expands the range of possible applications,
Fundamental importance in high-tech industry – they find application in data components, electromotive mechanisms, medical equipment, as well as modern systems.
Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Disadvantages of NdFeB magnets:

At very strong impacts they can crack, therefore we recommend placing them in special holders. A metal housing provides additional protection against damage and increases the magnet's durability.
NdFeB magnets lose power when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of power (a factor is the shape and dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
They oxidize in a humid environment - during use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
Limited ability of making threads in the magnet and complex shapes - recommended is cover - magnetic holder.
Potential hazard related to microscopic parts of magnets are risky, when accidentally swallowed, which gains importance in the aspect of protecting the youngest. It is also worth noting that small components of these devices can complicate diagnosis medical after entering the body.
With large orders the cost of neodymium magnets is a challenge,

Maximum holding power of the magnet – what contributes to it?

Magnet power is the result of a measurement for the most favorable conditions, taking into account:

on a base made of mild steel, perfectly concentrating the magnetic field
with a thickness no less than 10 mm
characterized by lack of roughness
with zero gap (no coatings)
for force applied at a right angle (pull-off, not shear)
at ambient temperature room level

Practical lifting capacity: influencing factors

Holding efficiency is influenced by specific conditions, such as (from most important):

Distance – the presence of foreign body (paint, dirt, gap) acts as an insulator, which lowers capacity steeply (even by 50% at 0.5 mm).
Loading method – declared lifting capacity refers to detachment vertically. When applying parallel force, the magnet holds much less (typically approx. 20-30% of nominal force).
Steel thickness – insufficiently thick plate causes magnetic saturation, causing part of the power to be escaped to the other side.
Steel grade – ideal substrate is pure iron steel. Cast iron may have worse magnetic properties.
Surface finish – ideal contact is possible only on smooth steel. Rough texture reduce the real contact area, weakening the magnet.
Thermal factor – hot environment weakens pulling force. Exceeding the limit temperature can permanently damage the magnet.

* Lifting capacity testing was carried out on a smooth plate of optimal thickness, under perpendicular forces, however under shearing force the load capacity is reduced by as much as 5 times. Moreover, even a minimal clearance {between} the magnet and the plate lowers the lifting capacity.

Warnings

Demagnetization risk

Keep cool. Neodymium magnets are sensitive to temperature. If you require resistance above 80°C, ask us about HT versions (H, SH, UH).

Risk of cracking

Despite metallic appearance, neodymium is delicate and not impact-resistant. Avoid impacts, as the magnet may shatter into sharp, dangerous pieces.

Choking Hazard

Neodymium magnets are not intended for children. Eating several magnets can lead to them connecting inside the digestive tract, which constitutes a severe health hazard and requires urgent medical intervention.

Finger safety

Protect your hands. Two large magnets will snap together immediately with a force of massive weight, destroying anything in their path. Be careful!

Danger to pacemakers

Warning for patients: Powerful magnets affect medical devices. Keep minimum 30 cm distance or request help to handle the magnets.

Machining danger

Drilling and cutting of NdFeB material carries a risk of fire hazard. Neodymium dust oxidizes rapidly with oxygen and is difficult to extinguish.

Avoid contact if allergic

Allergy Notice: The nickel-copper-nickel coating consists of nickel. If skin irritation happens, immediately stop handling magnets and use protective gear.

Threat to navigation

A strong magnetic field disrupts the operation of compasses in phones and GPS navigation. Maintain magnets close to a smartphone to avoid breaking the sensors.

Data carriers

Intense magnetic fields can destroy records on payment cards, HDDs, and storage devices. Keep a distance of at least 10 cm.

Handling guide

Before use, read the rules. Sudden snapping can destroy the magnet or injure your hand. Be predictive.

Important!

Learn more about hazards in the article: Safety of working with magnets.

MP 30x7/3x3 / N38 - ring magnet

MP 30x7/3x3 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Physical simulation of the product - technical parameters

1. Montaż na Ścianie (Ześlizg)

2. Wpływ Grubości Blachy

3. Wytrzymałość Temperaturowa

Magnet Pull Force

Magnetic Field

Jak rozdzielać?

Elektronika

Rozruszniki Serca

Nie dla dzieci

Kruchy materiał

Do czego użyć tego magnesu?

Elektronika i Czujniki

Modelarstwo i Druk 3D

Meble i Fronty

Other deals

UMGGZ 34x6 [M4] GZ / N38 - rubber magnetic holder external thread

AM szekla [M10] - magnetic accessories

SM 25x250 [2xM8] / N42 - magnetic separator

MW 20x35 / N38 - cylindrical magnet

Pros and cons of rare earth magnets.

Maximum holding power of the magnet – what contributes to it?

Practical lifting capacity: influencing factors

Warnings

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C