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MP 25x13x8 / 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 030191

GTIN/EAN: 5906301812081

5.00

Diameter

25 mm [±0,1 mm]

internal diameter Ø

13 mm [±0,1 mm]

Height

8 mm [±0,1 mm]

Weight

21.49 g

Magnetization Direction

↑ axial

Load capacity

10.49 kg / 102.90 N

Magnetic Induction

334.09 mT / 3341 Gs

Coating

[NiCuNi] Nickel

13.53 ZŁ with VAT / pcs + price for transport

11.00 ZŁ net + 23% VAT / pcs

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MP 25x13x8 / N38 - ring magnet

Specification / characteristics MP 25x13x8 / N38 - ring magnet

properties

properties	values
Cat. no.	030191
GTIN/EAN	5906301812081
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	13 mm [±0,1 mm]
Height	8 mm [±0,1 mm]
Weight	21.49 g
Magnetization Direction	↑ axial
Load capacity ~ ?	10.49 kg / 102.90 N
Magnetic Induction ~ ?	334.09 mT / 3341 Gs
Coating	[NiCuNi] Nickel
Manufacturing Tolerance	±0.1 mm

Magnetic properties of material N38

Specification / characteristics MP 25x13x8 / N38 - ring magnet

properties	values	units
remenance Br [min. - max.] ?	12.2-12.6	kGs
remenance Br [min. - max.] ?	1220-1260	mT
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 10^-6	°C^-1
Thermal expansion perpendicular (⊥) to orientation (M)	-(1-3) x 10^-6	°C^-1
Young's modulus	1.7 x 10⁴	kg/mm²

Engineering analysis of the assembly - report

Presented data are the outcome of a physical calculation. Values rely on algorithms for the material Nd₂Fe₁₄B. Operational performance might slightly differ. Please consider these calculations as a reference point when designing systems.

Table 1: Static force (pull vs distance) - power drop
MP 25x13x8 / N38

Distance (mm)	Induction (Gauss) / mT	Pull Force (kg)	Risk Status
0 mm	5777 Gs 577.7 mT	10.49 kg / 10490.0 g 102.9 N	crushing
1 mm	5310 Gs 531.0 mT	8.86 kg / 8861.7 g 86.9 N	medium risk
2 mm	4846 Gs 484.6 mT	7.38 kg / 7379.4 g 72.4 N	medium risk
3 mm	4397 Gs 439.7 mT	6.08 kg / 6077.4 g 59.6 N	medium risk
5 mm	3576 Gs 357.6 mT	4.02 kg / 4019.0 g 39.4 N	medium risk
10 mm	2073 Gs 207.3 mT	1.35 kg / 1350.2 g 13.2 N	weak grip
15 mm	1231 Gs 123.1 mT	0.48 kg / 476.4 g 4.7 N	weak grip
20 mm	773 Gs 77.3 mT	0.19 kg / 187.6 g 1.8 N	weak grip
30 mm	356 Gs 35.6 mT	0.04 kg / 39.8 g 0.4 N	weak grip
50 mm	115 Gs 11.5 mT	0.00 kg / 4.1 g 0.0 N	weak grip

Magnetic force decreases drastically with every mm of gap. Note that even a very thin break (e.g., contamination, paint, rust) strongly weakens the grip. Magnets operate optimally in perfect adhesion; air break kills the force. See how rapidly the parameters fall, when the magnet does not touch flatly to the steel surface. When designing the mounting, avoid redundant distances.

Table 2: Shear capacity (vertical surface)
MP 25x13x8 / N38

Distance (mm)	Friction coefficient	Pull Force (kg)
0 mm	Stal (~0.2)	2.10 kg / 2098.0 g 20.6 N
1 mm	Stal (~0.2)	1.77 kg / 1772.0 g 17.4 N
2 mm	Stal (~0.2)	1.48 kg / 1476.0 g 14.5 N
3 mm	Stal (~0.2)	1.22 kg / 1216.0 g 11.9 N
5 mm	Stal (~0.2)	0.80 kg / 804.0 g 7.9 N
10 mm	Stal (~0.2)	0.27 kg / 270.0 g 2.6 N
15 mm	Stal (~0.2)	0.10 kg / 96.0 g 0.9 N
20 mm	Stal (~0.2)	0.04 kg / 38.0 g 0.4 N
30 mm	Stal (~0.2)	0.01 kg / 8.0 g 0.1 N
50 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N

The table below shows the approximate force needed to initiate the downward movement of the magnet down along a upright steel plate (assuming standard friction). This value depends on the gap size between the magnet and the metal.

Table 3: Vertical assembly (shearing) - vertical pull
MP 25x13x8 / N38

Surface type	Friction coefficient / % Mocy	Max load (kg)
Raw steel	µ = 0.3 30% Nominalnej Siły	3.15 kg / 3147.0 g 30.9 N
Painted steel (standard)	µ = 0.2 20% Nominalnej Siły	2.10 kg / 2098.0 g 20.6 N
Oily/slippery steel	µ = 0.1 10% Nominalnej Siły	1.05 kg / 1049.0 g 10.3 N
Magnet with anti-slip rubber	µ = 0.5 50% Nominalnej Siły	5.25 kg / 5245.0 g 51.5 N

When placing a holder on a vertical wall (e.g., a car body), it will maintain just approx. 1/5 of nominal attraction strength. Gravity as well as a low friction coefficient influence the fact that products move down faster than they pull off. Planning a vertical fastening? Note that the shear force is significantly lower than the perpendicular breakaway force. On a painted metal, the element will give way down under a significantly smaller load. Using a rubber pad can drastically raise the stability.

Table 4: Material efficiency (saturation) - power losses
MP 25x13x8 / N38

Steel thickness (mm)	% power	Real pull force (kg)
0.5 mm	5%	0.52 kg / 524.5 g 5.1 N
1 mm	13%	1.31 kg / 1311.3 g 12.9 N
2 mm	25%	2.62 kg / 2622.5 g 25.7 N
5 mm	63%	6.56 kg / 6556.3 g 64.3 N
10 mm	100%	10.49 kg / 10490.0 g 102.9 N

A thin sheet is not enough to take in the entire magnetic field, which wastes potential of the magnet. If you mount a strong magnet to a too thin substrate, the flux will penetrate right through and the pull force will drop sharply. To utilize full efficiency of this neodymium's potential, you require a sufficiently solid element of metal. The saturation phenomenon causes that on delicate walls (e.g., appliance housings), the magnet works worse. We recommend selecting the steel thickness according to the table below.

Table 5: Working in heat (stability) - resistance threshold
MP 25x13x8 / N38

Ambient temp. (°C)	Power loss	Remaining pull	Status
20 °C	0.0%	10.49 kg / 10490.0 g 102.9 N	OK
40 °C	-2.2%	10.26 kg / 10259.2 g 100.6 N	OK
60 °C	-4.4%	10.03 kg / 10028.4 g 98.4 N	OK
80 °C	-6.6%	9.80 kg / 9797.7 g 96.1 N
100 °C	-28.8%	7.47 kg / 7468.9 g 73.3 N

Classic neodymiums irreversibly lose strength above the temperature limit. Protect against heat – excessive heat can permanently destroy this product. As the temperature rises, the magnet's power temporarily decreases. Avoid using this product near heat sources higher than its working range. Too high temperature will lead to permanent loss of magnetism.

*Important note: Heat tolerance depends not only on the material grade, and the Permeance Coefficient Pc. Flat magnets (low permeance coefficient) are more susceptible to demagnetization sooner compared to rod magnets. The danger warning in the table signals a risk of irreversible loss for this particular item.

Table 6: Two magnets (repulsion) - forces in the system
MP 25x13x8 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	77.07 kg / 77067 g 756.0 N 6 082 Gs	N/A
1 mm	71.01 kg / 71011 g 696.6 N 11 091 Gs	63.91 kg / 63910 g 627.0 N ~0 Gs
2 mm	65.10 kg / 65105 g 638.7 N 10 620 Gs	58.59 kg / 58594 g 574.8 N ~0 Gs
3 mm	59.50 kg / 59500 g 583.7 N 10 153 Gs	53.55 kg / 53550 g 525.3 N ~0 Gs
5 mm	49.26 kg / 49263 g 483.3 N 9 238 Gs	44.34 kg / 44336 g 434.9 N ~0 Gs
10 mm	29.53 kg / 29527 g 289.7 N 7 152 Gs	26.57 kg / 26574 g 260.7 N ~0 Gs
20 mm	9.92 kg / 9919 g 97.3 N 4 145 Gs	8.93 kg / 8927 g 87.6 N ~0 Gs
50 mm	0.61 kg / 605 g 5.9 N 1 024 Gs	0.54 kg / 545 g 5.3 N ~0 Gs

Two magnets attract each other from a much further distance than a magnet and sheet setup. The setup of magnet-to-magnet produces a massive flux and a wider radius of performance. Planning to create a powerful holder? Utilize two neodymiums instead of a neodymium and a steel. Be careful that when bringing together two magnets, the collision energy is extreme. The levitation is slightly lower than the attraction, but still large.
*The magnetic induction between like poles drops to ~0 Gs in the exact middle of the gap (due to field cancellation).

Table 7: Hazards (electronics) - precautionary measures
MP 25x13x8 / 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
Mechanical watch	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

A strong magnetic field poses a serious hazard to electronics and pacemakers. These NdFeB products produce a flux that destroys function of sensitive medical devices. Be aware: the invisible magnetic field acts through matter and glass. Exceptional care must be exercised by people with cochlear implants and insulin pumps. Influence will be felt by: mechanical watches, remotes, membranes, and screens. Do not bring the product near payment cards, hard drives, or sensitive navigation tools.

Table 8: Impact energy (kinetic energy) - collision effects
MP 25x13x8 / N38

Start from (mm)	Speed (km/h)	Energy (J)
10 mm	24.01 km/h (6.67 m/s)	0.48 J
30 mm	38.68 km/h (10.75 m/s)	1.24 J
50 mm	49.84 km/h (13.84 m/s)	2.06 J
100 mm	70.46 km/h (19.57 m/s)	4.12 J

NdFeB products are very brittle – a collision with steel risks their cracking. Pay attention to connection velocity – a magnet released freely becomes dangerous. Kinetic force can destroy the magnet or painful pinches to fingers. Hold the magnet firmly during mounting so it doesn't hit violently against the steel surface. A contact at a velocity of dozens of km/h means shattering of the neodymium. Wear safety glasses when playing with large magnets.

Table 9: Corrosion resistance
MP 25x13x8 / 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 following table defines the conditions under which this product can be safely used. Note the thickness of the protective layer.

Table 10: Electrical data (Flux)
MP 25x13x8 / N38

Parameter	Value	SI Unit / Description
Magnetic Flux	23 118 Mx	231.2 µWb
P_c Coefficient	1.04	High (Stable)

Flux value passing through the pole surface. Essential parameter for generator designers as well as sensors. P_c value defines the working geometry.

Table 11: Physics of underwater searching
MP 25x13x8 / N38

Environment	Effective steel pull	Effect
Air (land)	10.49 kg	Standard
Water (riverbed)	12.01 kg (+1.52 kg Buoyancy gain)	+14.5%

Corrosion warning: Standard nickel requires drying after every contact with moisture; lack of maintenance will lead to rust spots.

In water, the magnet feels stronger thanks to Archimedes' principle. Buoyancy helps in lifting finds.

1. Shear force

*Warning: On a vertical surface, the magnet holds just a fraction of its max power.

2. Steel saturation

*Thin metal sheet (e.g. 0.5mm PC case) drastically limits the holding force.

3. Thermal stability

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

4. Demagnetization curve and operating point (B-H)

chart generated for the permeance coefficient P_c (Permeance Coefficient) = 1.04

This simulation demonstrates the magnetic stability of the selected magnet under specific geometric conditions. The solid red line represents the demagnetization curve (material potential), while the dashed blue line is the load line based on the magnet's geometry. The P_c (Permeance Coefficient), also known as the load line slope, is a dimensionless value that describes the relationship between the magnet's shape and its magnetic stability. The intersection of these two lines (the black dot) is the operating point — it determines the actual magnetic flux density generated by the magnet in this specific configuration. A higher P_c value means the magnet is more 'slender' (tall relative to its area), resulting in a higher operating point and better resistance to irreversible demagnetization caused by external fields or temperature. A value of 0.42 is relatively low (typical for flat magnets), meaning the operating point is closer to the 'knee' of the curve — caution is advised when operating at temperatures near the maximum limit to avoid strength loss.

Technical and environmental data

Chemical composition

iron (Fe)	64% – 68%
neodymium (Nd)	29% – 32%
boron (B)	1.1% – 1.2%
dysprosium (Dy)	0.5% – 2.0%
coating (Ni-Cu-Ni)	< 0.05%

Sustainability

recyclability (EoL)	100%
recycled raw materials	~10% (pre-cons)
carbon footprint	low / zredukowany
waste code (EWC)	16 02 16

Safety card (GPSR)

responsible entity

Dhit sp. z o.o.

ul. Kościuszki 6A, 05-850 Ożarów Mazowiecki

tel: +48 22 499 98 98 | e-mail: bok@dhit.pl

batch number/type

id: 030191-2025

Quick Unit Converter

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Kilograms (kg)

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The ring-shaped magnet MP 25x13x8 / N38 is created for permanent mounting, where glue might fail or be insufficient. Mounting is clean and reversible, unlike gluing. It is also often used in advertising for fixing signs and in workshops for organizing tools.

This is a crucial issue when working with model MP 25x13x8 / N38. Neodymium magnets are sintered ceramics, which means they are very brittle and inelastic. One turn too many can destroy the magnet, so do it slowly. 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 is not sufficient for rain. In the place of the mounting hole, the coating is thinner and easily scratched when tightening the screw, which will become a corrosion focus. This product is dedicated for indoor use. For outdoor applications, we recommend choosing rubberized holders or additional protection with varnish.

The inner hole diameter determines the maximum size of the mounting element. For magnets with a straight hole, a conical head can act like a wedge and burst the magnet. Always check that the screw head is not larger than the outer diameter of the magnet (25 mm), so it doesn't protrude beyond the outline.

The presented product is a ring magnet with dimensions Ø25 mm (outer diameter) and height 8 mm. The pulling force of this model is an impressive 10.49 kg, which translates to 102.90 N in newtons. The product has a [NiCuNi] coating and is made of NdFeB material. Inner hole dimension: 13 mm.

The poles are located on the planes with holes, not on the sides of the ring. 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). 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.

Strengths

Besides their stability, neodymium magnets are valued for these benefits:

They virtually do not lose strength, because even after 10 years the performance loss is only ~1% (based on calculations),
Magnets effectively defend themselves against loss of magnetization caused by external fields,
In other words, due to the smooth finish of nickel, the element is aesthetically pleasing,
They are known for high magnetic induction at the operating surface, which affects their effectiveness,
Due to their durability and thermal resistance, neodymium magnets can operate (depending on the form) even at high temperatures reaching 230°C or more...
Thanks to the possibility of accurate shaping and adaptation to custom projects, magnetic components can be manufactured in a variety of geometric configurations, which expands the range of possible applications,
Significant place in advanced technology sectors – they are used in HDD drives, electric drive systems, medical devices, and multitasking production systems.
Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which allows their use in compact constructions

Disadvantages

Disadvantages of NdFeB magnets:

At strong impacts they can break, therefore we recommend placing them in special holders. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
When exposed to high temperature, neodymium magnets experience a drop in force. Often, when the temperature exceeds 80°C, their power 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. For applications 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 complex forms - recommended is a housing - mounting mechanism.
Possible danger to health – tiny shards of magnets pose a threat, if swallowed, which is particularly important in the aspect of protecting the youngest. Additionally, small components of these products 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

Magnetic strength at its maximum – what it depends on?

Holding force of 10.49 kg is a result of laboratory testing executed under standard conditions:

using a plate made of high-permeability steel, serving as a ideal flux conductor
possessing a thickness of minimum 10 mm to ensure full flux closure
characterized by smoothness
without the slightest insulating layer between the magnet and steel
under perpendicular application of breakaway force (90-degree angle)
in temp. approx. 20°C

Magnet lifting force in use – key factors

Bear in mind that the working load will differ influenced by the following factors, in order of importance:

Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by varnish or dirt) diminishes the pulling force, often by half at just 0.5 mm.
Loading method – catalog parameter refers to pulling vertically. When attempting to slide, the magnet exhibits significantly lower power (typically approx. 20-30% of maximum force).
Substrate thickness – for full efficiency, the steel must be adequately massive. Paper-thin metal limits the lifting capacity (the magnet "punches through" it).
Plate material – mild steel gives the best results. Higher carbon content lower magnetic permeability and holding force.
Surface condition – ground elements ensure maximum contact, which increases force. Rough surfaces weaken the grip.
Temperature influence – hot environment reduces pulling force. Too high temperature can permanently damage the magnet.

Holding force was checked on the plate surface of 20 mm thickness, when a perpendicular force was applied, in contrast under attempts to slide the magnet the holding force is lower. Moreover, even a slight gap between the magnet and the plate decreases the lifting capacity.

Safety rules for work with NdFeB magnets

Safe distance

Powerful magnetic fields can destroy records on payment cards, HDDs, and other magnetic media. Maintain a gap of at least 10 cm.

Pacemakers

Warning for patients: Strong magnetic fields affect medical devices. Keep minimum 30 cm distance or ask another person to handle the magnets.

Fire risk

Machining of neodymium magnets poses a fire risk. Magnetic powder oxidizes rapidly with oxygen and is hard to extinguish.

Magnet fragility

Neodymium magnets are sintered ceramics, meaning they are prone to chipping. Impact of two magnets will cause them shattering into small pieces.

Danger to the youngest

Strictly store magnets out of reach of children. Ingestion danger is high, and the consequences of magnets connecting inside the body are tragic.

Allergy Warning

Some people have a hypersensitivity to nickel, which is the typical protective layer for neodymium magnets. Extended handling can result in skin redness. It is best to use safety gloves.

Keep away from electronics

A strong magnetic field interferes with the functioning of magnetometers in smartphones and navigation systems. Keep magnets close to a smartphone to prevent breaking the sensors.

Immense force

Use magnets consciously. Their immense force can surprise even experienced users. Stay alert and respect their power.

Crushing risk

Large magnets can break fingers instantly. Under no circumstances put your hand between two attracting surfaces.

Operating temperature

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

Safety First! Want to know more? Check our post: Are neodymium magnets dangerous?

MP 25x13x8 / N38 - ring magnet

Want to talk magnets?

MP 25x13x8 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Engineering analysis of the assembly - report

1. Shear force

2. Steel saturation

3. Thermal stability

4. Demagnetization curve and operating point (B-H)

Chemical composition

Sustainability

Magnet pull force

Field Strength

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Pros and cons of rare earth magnets.

Strengths

Disadvantages

Holding force characteristics

Magnetic strength at its maximum – what it depends on?

Magnet lifting force in use – key factors

Safe distance

Pacemakers

Fire risk

Magnet fragility

Danger to the youngest

Allergy Warning

Keep away from electronics

Immense force

Crushing risk

Operating temperature

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C