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MP 25x7x9 / 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 030195

GTIN: 5906301812128

5.00

Diameter

25 mm [±0,1 mm]

internal diameter Ø

7 mm [±0,1 mm]

Height

9 mm [±0,1 mm]

Weight

30.54 g

Magnetization Direction

↑ axial

Load capacity

14.82 kg / 145.39 N

Magnetic Induction

362.13 mT / 3621 Gs

Coating

[NiCuNi] Nickel

12.55 ZŁ with VAT / pcs + price for transport

10.20 ZŁ net + 23% VAT / pcs

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MP 25x7x9 / N38 - ring magnet

Specification / characteristics MP 25x7x9 / N38 - ring magnet

properties

properties	values
Cat. no.	030195
GTIN	5906301812128
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	25 mm [±0,1 mm]
internal diameter Ø	7 mm [±0,1 mm]
Height	9 mm [±0,1 mm]
Weight	30.54 g
Magnetization Direction	↑ axial
Load capacity ~ ?	14.82 kg / 145.39 N
Magnetic Induction ~ ?	362.13 mT / 3621 Gs
Coating	[NiCuNi] Nickel
Manufacturing Tolerance	±0.1 mm

Magnetic properties of material N38

Specification / characteristics MP 25x7x9 / 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 magnet - technical parameters

The following values constitute the result of a mathematical simulation. Values are based on algorithms for the class Nd₂Fe₁₄B. Operational conditions might slightly deviate from the simulation results. Please consider these data as a reference point during assembly planning.

Table 1: Static pull force (force vs gap) - interaction chart
MP 25x7x9 / N38

Distance (mm)	Induction (Gauss) / mT	Pull Force (kg)	Risk Status
0 mm	5777 Gs 577.7 mT	14.82 kg / 14820.0 g 145.4 N	critical level
1 mm	5310 Gs 531.0 mT	12.52 kg / 12519.6 g 122.8 N	critical level
2 mm	4846 Gs 484.6 mT	10.43 kg / 10425.5 g 102.3 N	critical level
3 mm	4397 Gs 439.7 mT	8.59 kg / 8586.1 g 84.2 N	strong
5 mm	3576 Gs 357.6 mT	5.68 kg / 5678.0 g 55.7 N	strong
10 mm	2073 Gs 207.3 mT	1.91 kg / 1907.5 g 18.7 N	safe
15 mm	1231 Gs 123.1 mT	0.67 kg / 673.1 g 6.6 N	safe
20 mm	773 Gs 77.3 mT	0.27 kg / 265.0 g 2.6 N	safe
30 mm	356 Gs 35.6 mT	0.06 kg / 56.2 g 0.6 N	safe
50 mm	115 Gs 11.5 mT	0.01 kg / 5.9 g 0.1 N	safe

Grip strength drops drastically with every mm of distance. Note that even a microscopic distance (e.g., contamination, paint, rust) strongly diminishes the holding power. Magnets work most effectively in perfect adhesion; distance kills the power. Notice how flashily the pull force drop, when the magnet does not adhere flatly to the metal substrate. When designing the mounting, avoid unnecessary gaps.

Table 2: Sliding Capacity (Vertical Surface)
MP 25x7x9 / N38

Distance (mm)	Friction coefficient	Pull Force (kg)
0 mm	Stal (~0.2)	2.96 kg / 2964.0 g 29.1 N
1 mm	Stal (~0.2)	2.50 kg / 2504.0 g 24.6 N
2 mm	Stal (~0.2)	2.09 kg / 2086.0 g 20.5 N
3 mm	Stal (~0.2)	1.72 kg / 1718.0 g 16.9 N
5 mm	Stal (~0.2)	1.14 kg / 1136.0 g 11.1 N
10 mm	Stal (~0.2)	0.38 kg / 382.0 g 3.7 N
15 mm	Stal (~0.2)	0.13 kg / 134.0 g 1.3 N
20 mm	Stal (~0.2)	0.05 kg / 54.0 g 0.5 N
30 mm	Stal (~0.2)	0.01 kg / 12.0 g 0.1 N
50 mm	Stal (~0.2)	0.00 kg / 2.0 g 0.0 N

This section defines the theoretical weight limit required to cause the downward movement of the magnet downwards on a vertical steel wall (considering standard friction). The holding force varies with the separation distance between the magnet and the metal.

Table 3: Wall mounting (shearing) - vertical pull
MP 25x7x9 / N38

Surface type	Friction coefficient / % Mocy	Max load (kg)
Raw steel	µ = 0.3 30% Nominalnej Siły	4.45 kg / 4446.0 g 43.6 N
Painted steel (standard)	µ = 0.2 20% Nominalnej Siły	2.96 kg / 2964.0 g 29.1 N
Oily/slippery steel	µ = 0.1 10% Nominalnej Siły	1.48 kg / 1482.0 g 14.5 N
Magnet with anti-slip rubber	µ = 0.5 50% Nominalnej Siły	7.41 kg / 7410.0 g 72.7 N

When hanging a element on a upright surface (e.g., a fridge), it will maintain just about 20%-30% of nominal attraction strength. Gravitational force and a low friction coefficient cause that holders slip easier than they pop off the substrate. Planning a vertical fastening? Remember that the shear force is much weaker than the maximum static pull force. On a smooth steel, the holder will slide down under a significantly smaller weight. Using a rubber pad can effectively improve the result.

Table 4: Material efficiency (substrate influence) - sheet metal selection
MP 25x7x9 / N38

Steel thickness (mm)	% power	Real pull force (kg)
0.5 mm	5%	0.74 kg / 741.0 g 7.3 N
1 mm	13%	1.85 kg / 1852.5 g 18.2 N
2 mm	25%	3.71 kg / 3705.0 g 36.3 N
5 mm	63%	9.26 kg / 9262.5 g 90.9 N
10 mm	100%	14.82 kg / 14820.0 g 145.4 N

A thin sheet cannot absorb the full magnetic flux, which wastes potential of the magnet. If you mount a strong magnet to a thin surface, the magnetism will pass right through and the pull force will drop sharply. To utilize 100% of this magnet's power, you need a suitably thick backing of steel. The saturation effect causes that on delicate walls (e.g., thin profiles), the holder holds weaker. We advise picking the steel dimension from these parameters.

Table 5: Working in heat (stability) - thermal limit
MP 25x7x9 / N38

Ambient temp. (°C)	Power loss	Remaining pull	Status
20 °C	0.0%	14.82 kg / 14820.0 g 145.4 N	OK
40 °C	-2.2%	14.49 kg / 14494.0 g 142.2 N	OK
60 °C	-4.4%	14.17 kg / 14167.9 g 139.0 N	OK
80 °C	-6.6%	13.84 kg / 13841.9 g 135.8 N
100 °C	-28.8%	10.55 kg / 10551.8 g 103.5 N

Classic neodymiums lose parameters above the temperature limit. Protect against heat – excessive heat can irreversibly destroy this product. With increasing heat, the neodymium's capacity momentarily drops. Refrain from using this magnet close to heaters higher than its safe range. Exceeding the critical threshold will lead to destruction of magnetism.

*Engineering note: Thermal stability depends not only on the material grade, and the Permeance Coefficient Pc. Flat magnets (low Pc) risk losing magnetic properties sooner than taller cylinders. The danger warning in the table points to permanent field degradation for this specific geometry.

Table 6: Magnet-Magnet interaction (repulsion) - forces in the system
MP 25x7x9 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	74.73 kg / 74732 g 733.1 N 6 082 Gs	N/A
1 mm	68.86 kg / 68859 g 675.5 N 11 091 Gs	61.97 kg / 61973 g 608.0 N ~0 Gs
2 mm	63.13 kg / 63132 g 619.3 N 10 620 Gs	56.82 kg / 56819 g 557.4 N ~0 Gs
3 mm	57.70 kg / 57697 g 566.0 N 10 153 Gs	51.93 kg / 51927 g 509.4 N ~0 Gs
5 mm	47.77 kg / 47770 g 468.6 N 9 238 Gs	42.99 kg / 42993 g 421.8 N ~0 Gs
10 mm	28.63 kg / 28632 g 280.9 N 7 152 Gs	25.77 kg / 25769 g 252.8 N ~0 Gs
20 mm	9.62 kg / 9619 g 94.4 N 4 145 Gs	8.66 kg / 8657 g 84.9 N ~0 Gs
50 mm	0.59 kg / 587 g 5.8 N 1 024 Gs	0.53 kg / 528 g 5.2 N ~0 Gs

Two strong neodymiums attract each other from a significantly greater distance than a magnet and sheet combination. Such a system of magnet-to-magnet generates a stronger field and a further horizon of action. Designing a solid fastener? Apply two magnets instead of a neodymium and a steel. Be careful that when bringing together two magnets, the pinch force is extreme. The levitation is slightly lower than the attraction, but still significant.
*Field value between like poles is approximately ~0 Gs in the exact middle between the magnets (caused by magnetic field nullification).

Table 7: Protective zones (electronics) - warnings
MP 25x7x9 / N38

Object / Device	Limit (Gauss) / mT	Safe distance
Pacemaker	5 Gs (0.5 mT)	17.0 cm
Hearing aid	10 Gs (1.0 mT)	13.5 cm
Timepiece	20 Gs (2.0 mT)	10.5 cm
Mobile device	40 Gs (4.0 mT)	8.0 cm
Remote	50 Gs (5.0 mT)	7.5 cm
Payment card	400 Gs (40.0 mT)	3.0 cm
HDD hard drive	600 Gs (60.0 mT)	2.5 cm

Powerful magnet radiation is a serious hazard to electronic devices and medical implants. These magnets generate a flux that disrupts operation of digital equipment. Be aware: the invisible magnetic field passes through tissues and plastic. Exceptional care must be taken by people with hearing aids and insulin pumps. Also at risk are: automatic timepieces, car keys, speakers, and screens. Do not bring the product near payment cards, hard drives, or sensitive navigation tools.

Table 8: Dynamics (kinetic energy) - collision effects
MP 25x7x9 / N38

Start from (mm)	Speed (km/h)	Energy (J)
10 mm	23.94 km/h (6.65 m/s)	0.68 J
30 mm	38.57 km/h (10.71 m/s)	1.75 J
50 mm	49.69 km/h (13.80 m/s)	2.91 J
100 mm	70.25 km/h (19.52 m/s)	5.82 J

NdFeB products are very brittle – a collision with steel risks their cracking. Watch the impact speed – a neodymium left loose turns into a projectile. Impact energy can trigger coating fragments or injury to fingers. Be sure to control the product during installation so it doesn't hit violently against the metal. A collision at high speed means shattering of the neodymium. Wear eye protection when handling with large magnets.

Table 9: Corrosion resistance
MP 25x7x9 / 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 (Pc)
MP 25x7x9 / N38

Parameter	Value	Jedn. SI / Opis
Strumień (Flux)	22 495 Mx	225.0 µWb
Współczynnik Pc	1.05	Wysoki (Stabilny)

Total magnetic flux flowing through the magnet pole. Key data for motor design and Hall effect devices. Pc Factor determines the working geometry.

Table 11: Physics of underwater searching
MP 25x7x9 / N38

Environment	Effective steel pull	Effect
Air (land)	14.82 kg	Standard
Water (riverbed)	16.97 kg (+2.15 kg Buoyancy gain)	+14.5%

Rust risk: Remember to wipe the magnet thoroughly after removing it from water and apply a protective layer (e.g., oil) to avoid corrosion.

Contrary to myths, water does not block the magnetic field. However, remember the water resistance when pulling the rope quickly.

1. Shear force

*Warning: On a vertical surface, the magnet retains merely approx. 20-30% of its nominal pull.

2. Efficiency vs thickness

*Thin steel (e.g. computer case) drastically weakens the holding force.

3. Temperature resistance

*For N38 material, the critical limit is 80°C.

Magnet Unit Converter

Pulling Force

Newtons (N)

Force in lbs

Magnetic Field

Tesla (T)

Input your value in just one field to see the conversion in the other units at once.

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The ring magnet with a hole MP 25x7x9 / N38 is created for mechanical fastening, where glue might fail or be insufficient. Thanks to the hole (often for a screw), this model enables quick installation to wood, wall, plastic, or metal. This product with a force of 14.82 kg works great as a cabinet closure, speaker holder, or mounting element in devices.

This is a crucial issue when working with model MP 25x7x9 / N38. Neodymium magnets are sintered ceramics, which means they are very brittle and inelastic. When tightening the screw, you must maintain caution. We recommend tightening manually with a screwdriver, not an impact driver, because excessive force will cause the ring to crack. It's a good idea to use a rubber spacer under the screw head, which will cushion the stresses. 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 does not ensure full waterproofing. In the place of the mounting hole, the coating is thinner and can be damaged when tightening the screw, which will become a corrosion focus. If you must use it outside, paint it with anti-corrosion paint after mounting.

A screw or bolt with a thread diameter smaller than 7 mm fits this model. For magnets with a straight hole, a conical head can act like a wedge and burst the magnet. Aesthetic mounting requires selecting the appropriate head size.

This model is characterized by dimensions Ø25x9 mm and a weight of 30.54 g. The pulling force of this model is an impressive 14.82 kg, which translates to 145.39 N in newtons. The mounting hole diameter is precisely 7 mm.

These magnets are magnetized axially (through the thickness), which means one flat side is the N pole and the other is S. If you want two such magnets screwed with cones facing each other (faces) to attract, you must connect them with opposite poles (N to S). When ordering a larger quantity, magnets are usually packed in stacks, where they are already naturally paired.

Pros and cons of rare earth magnets.

Advantages

In addition to their long-term stability, neodymium magnets provide the following advantages:

They do not lose magnetism, even after around 10 years – the decrease in strength is only ~1% (based on measurements),
Neodymium magnets remain extremely resistant to magnetic field loss caused by magnetic disturbances,
In other words, due to the metallic surface of nickel, the element becomes visually attractive,
They feature high magnetic induction at the operating surface, which increases their power,
Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
In view of the possibility of free molding and customization to custom needs, magnetic components can be produced in a broad palette of shapes and sizes, which expands the range of possible applications,
Versatile presence in modern industrial fields – they find application in data components, electric motors, advanced medical instruments, also modern systems.
Compactness – despite small sizes they offer powerful magnetic field, making them ideal for precision applications

Disadvantages

Problematic aspects of neodymium magnets: application proposals

At very strong impacts they can crack, therefore we advise placing them in steel cases. A metal housing provides additional protection against damage and increases the magnet's durability.
When exposed to high temperature, neodymium magnets suffer a drop in force. Often, when the temperature exceeds 80°C, their strength decreases (depending on the size, as well as shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
When exposed to humidity, magnets usually rust. To use them in conditions outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation and corrosion.
Limited ability of making nuts in the magnet and complicated shapes - preferred is a housing - magnet mounting.
Possible danger related to microscopic parts of magnets are risky, when accidentally swallowed, which is particularly important in the aspect of protecting the youngest. Additionally, small elements of these devices can complicate diagnosis medical when they are in the body.
Higher cost of purchase is one of the disadvantages compared to ceramic magnets, especially in budget applications

Holding force characteristics

Maximum lifting capacity of the magnet – what it depends on?

The load parameter shown refers to the maximum value, recorded under optimal environment, specifically:

using a sheet made of mild steel, serving as a magnetic yoke
whose transverse dimension is min. 10 mm
with an polished contact surface
under conditions of no distance (surface-to-surface)
during detachment in a direction perpendicular to the plane
in temp. approx. 20°C

Determinants of practical lifting force of a magnet

Effective lifting capacity is affected by specific conditions, such as (from priority):

Gap (betwixt the magnet and the metal), since even a tiny distance (e.g. 0.5 mm) leads to a reduction in force by up to 50% (this also applies to paint, rust or dirt).
Force direction – catalog parameter refers to pulling vertically. When slipping, the magnet holds much less (often approx. 20-30% of nominal force).
Wall thickness – thin material does not allow full use of the magnet. Part of the magnetic field passes through the material instead of converting into lifting capacity.
Steel grade – ideal substrate is pure iron steel. Hardened steels may generate lower lifting capacity.
Surface condition – ground elements ensure maximum contact, which improves force. Rough surfaces weaken the grip.
Temperature – heating the magnet results in weakening of force. Check the thermal limit for a given model.

Holding force was tested on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, however under attempts to slide the magnet the holding force is lower. Moreover, even a small distance between the magnet and the plate decreases the holding force.

H&S for magnets

Implant safety

Patients with a heart stimulator must keep an absolute distance from magnets. The magnetic field can stop the functioning of the life-saving device.

Bodily injuries

Protect your hands. Two powerful magnets will join immediately with a force of massive weight, crushing anything in their path. Be careful!

Immense force

Be careful. Neodymium magnets attract from a long distance and connect with massive power, often quicker than you can react.

Cards and drives

Avoid bringing magnets close to a wallet, computer, or TV. The magnetism can destroy these devices and erase data from cards.

GPS and phone interference

GPS units and mobile phones are highly sensitive to magnetic fields. Direct contact with a powerful NdFeB magnet can decalibrate the internal compass in your phone.

Fire warning

Mechanical processing of NdFeB material carries a risk of fire risk. Neodymium dust oxidizes rapidly with oxygen and is hard to extinguish.

Nickel allergy

Nickel alert: The nickel-copper-nickel coating contains nickel. If redness occurs, cease working with magnets and use protective gear.

Thermal limits

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

Product not for children

These products are not toys. Accidental ingestion of multiple magnets may result in them connecting inside the digestive tract, which poses a severe health hazard and requires immediate surgery.

Magnet fragility

Watch out for shards. Magnets can fracture upon uncontrolled impact, ejecting sharp fragments into the air. Eye protection is mandatory.

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

MP 25x7x9 / N38 - ring magnet

Want to negotiate?

MP 25x7x9 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Physical simulation of the magnet - technical parameters

1. Shear force

2. Efficiency vs thickness

3. Temperature resistance

Pulling Force

Magnetic Field

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MW 2x10 / N38 - cylindrical magnet

Pros and cons of rare earth magnets.

Advantages

Disadvantages

Holding force characteristics

Maximum lifting capacity of the magnet – what it depends on?

Determinants of practical lifting force of a magnet

Implant safety

Bodily injuries

Immense force

Cards and drives

GPS and phone interference

Fire warning

Nickel allergy

Thermal limits

Product not for children

Magnet fragility

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C