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MP 25x13x8 / N38 - ring magnet

ring magnet

Catalog no 030191

GTIN/EAN: 5906301812081

5.00
Load capacity 10.49 kg / 102.90 N Magnetic Induction 334.09 mT / 3341 Gs
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
Coating
[NiCuNi] Nickel

How we measure these parameters — certificates and measurements

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Net
Gross
price from 1 pcs
11.00 zł
13.53 zł
price from 60 pcs
10.34 zł
12.72 zł
price from 230 pcs
9.68 zł
11.91 zł

Frequently asked questions

What is the hole in a ring magnet for?
For mounting on a screw or a shaft. The bore may be cylindrical or countersunk for a screw head. The hole removes magnet volume, so a ring holds less than a disc of the same outside diameter.
What is the polarisation?
Axial as standard — poles on the flat faces of the ring. Diametrical polarisation is made to order.
What sizes are available?
Outside diameter from 5 to 62 mm from stock. To order up to 200 mm outside diameter, 180 mm bore and 40 mm height, with a lead time of 25–35 days.

Engineering report for this magnet

Full PDF analysis: pull and shear force, effect of distance, temperature and plate thickness, safety distances and the demagnetization curve.

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Call us now +48 888 99 98 98 alternatively let us know using contact form the contact section.
Specifications and structure of a neodymium magnet can be estimated using our power calculator.

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Physical properties - 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
Remanence Br ? 12.2-12.6 kGs
Remanence Br ? 1220-1260 mT
Coercivity bHc ? 10.8-11.5 kOe
Coercivity bHc ? 860-915 kA/m
Intrinsic coercivity iHc ≥ 12 kOe
Intrinsic coercivity iHc ≥ 955 kA/m
Energy product BHmax ? 36-38 BH max MGOe
Energy product BHmax ? 287-303 BH max KJ/m
Maximum working temperature ? ≤ 80 °C

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°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 310 °C
Curie Temperature TF 590 °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

Physical analysis of the magnet - technical parameters

The following values are the direct effect of a physical simulation. Results are based on models for the class Nd2Fe14B. Operational parameters might slightly differ. Treat these data as a reference point for designers.

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

Distance (mm) Induction (Gauss) / mT Pull Force (kg/lbs/g/N) Risk Status
0 mm 5777 Gs
577.7 mT
10.49 kg / 23.13 lbs
10490.0 g / 102.9 N
critical level
1 mm 5310 Gs
531.0 mT
8.86 kg / 19.54 lbs
8861.7 g / 86.9 N
strong
2 mm 4846 Gs
484.6 mT
7.38 kg / 16.27 lbs
7379.4 g / 72.4 N
strong
3 mm 4397 Gs
439.7 mT
6.08 kg / 13.40 lbs
6077.4 g / 59.6 N
strong
5 mm 3576 Gs
357.6 mT
4.02 kg / 8.86 lbs
4019.0 g / 39.4 N
strong
10 mm 2073 Gs
207.3 mT
1.35 kg / 2.98 lbs
1350.2 g / 13.2 N
weak grip
15 mm 1231 Gs
123.1 mT
0.48 kg / 1.05 lbs
476.4 g / 4.7 N
weak grip
20 mm 773 Gs
77.3 mT
0.19 kg / 0.41 lbs
187.6 g / 1.8 N
weak grip
30 mm 356 Gs
35.6 mT
0.04 kg / 0.09 lbs
39.8 g / 0.4 N
weak grip
50 mm 115 Gs
11.5 mT
0.00 kg / 0.01 lbs
4.1 g / 0.0 N
weak grip

Table 2: Sliding hold (wall)
MP 25x13x8 / N38

Distance (mm) Friction coefficient Pull Force (kg/lbs/g/N)
0 mm Stal (~0.2) 2.10 kg / 4.63 lbs
2098.0 g / 20.6 N
1 mm Stal (~0.2) 1.77 kg / 3.91 lbs
1772.0 g / 17.4 N
2 mm Stal (~0.2) 1.48 kg / 3.25 lbs
1476.0 g / 14.5 N
3 mm Stal (~0.2) 1.22 kg / 2.68 lbs
1216.0 g / 11.9 N
5 mm Stal (~0.2) 0.80 kg / 1.77 lbs
804.0 g / 7.9 N
10 mm Stal (~0.2) 0.27 kg / 0.60 lbs
270.0 g / 2.6 N
15 mm Stal (~0.2) 0.10 kg / 0.21 lbs
96.0 g / 0.9 N
20 mm Stal (~0.2) 0.04 kg / 0.08 lbs
38.0 g / 0.4 N
30 mm Stal (~0.2) 0.01 kg / 0.02 lbs
8.0 g / 0.1 N
50 mm Stal (~0.2) 0.00 kg / 0.00 lbs
0.0 g / 0.0 N

Table 3: Vertical assembly (shearing) - behavior on slippery surfaces
MP 25x13x8 / N38

Surface type Friction coefficient / % Mocy Max load (kg/lbs/g/N)
Raw steel
µ = 0.3 30% Nominalnej Siły
3.15 kg / 6.94 lbs
3147.0 g / 30.9 N
Painted steel (standard)
µ = 0.2 20% Nominalnej Siły
2.10 kg / 4.63 lbs
2098.0 g / 20.6 N
Oily/slippery steel
µ = 0.1 10% Nominalnej Siły
1.05 kg / 2.31 lbs
1049.0 g / 10.3 N
Magnet with anti-slip rubber
µ = 0.5 50% Nominalnej Siły
5.25 kg / 11.56 lbs
5245.0 g / 51.5 N

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

Steel thickness (mm) % power Real pull force (kg/lbs/g/N)
0.5 mm
5%
0.52 kg / 1.16 lbs
524.5 g / 5.1 N
1 mm
13%
1.31 kg / 2.89 lbs
1311.3 g / 12.9 N
2 mm
25%
2.62 kg / 5.78 lbs
2622.5 g / 25.7 N
3 mm
38%
3.93 kg / 8.67 lbs
3933.8 g / 38.6 N
5 mm
63%
6.56 kg / 14.45 lbs
6556.3 g / 64.3 N
10 mm
100%
10.49 kg / 23.13 lbs
10490.0 g / 102.9 N
11 mm
100%
10.49 kg / 23.13 lbs
10490.0 g / 102.9 N
12 mm
100%
10.49 kg / 23.13 lbs
10490.0 g / 102.9 N

Table 5: Working in heat (material behavior) - thermal limit
MP 25x13x8 / N38

Ambient temp. (°C) Power loss Remaining pull (kg/lbs/g/N) Status
20 °C 0.0% 10.49 kg / 23.13 lbs
10490.0 g / 102.9 N
OK
40 °C -2.2% 10.26 kg / 22.62 lbs
10259.2 g / 100.6 N
OK
60 °C -4.4% 10.03 kg / 22.11 lbs
10028.4 g / 98.4 N
OK
80 °C -6.6% 9.80 kg / 21.60 lbs
9797.7 g / 96.1 N
100 °C -28.8% 7.47 kg / 16.47 lbs
7468.9 g / 73.3 N

Table 6: Magnet-Magnet interaction (attraction) - field collision
MP 25x13x8 / N38

Gap (mm) Attraction (kg/lbs) (N-S) Shear Strength (kg/lbs/g/N) Repulsion (kg/lbs) (N-N)
0 mm 77.07 kg / 169.90 lbs
6 082 Gs
11.56 kg / 25.49 lbs
11560 g / 113.4 N
N/A
1 mm 71.01 kg / 156.55 lbs
11 091 Gs
10.65 kg / 23.48 lbs
10652 g / 104.5 N
63.91 kg / 140.90 lbs
~0 Gs
2 mm 65.10 kg / 143.53 lbs
10 620 Gs
9.77 kg / 21.53 lbs
9766 g / 95.8 N
58.59 kg / 129.18 lbs
~0 Gs
3 mm 59.50 kg / 131.17 lbs
10 153 Gs
8.92 kg / 19.68 lbs
8925 g / 87.6 N
53.55 kg / 118.06 lbs
~0 Gs
5 mm 49.26 kg / 108.61 lbs
9 238 Gs
7.39 kg / 16.29 lbs
7389 g / 72.5 N
44.34 kg / 97.74 lbs
~0 Gs
10 mm 29.53 kg / 65.10 lbs
7 152 Gs
4.43 kg / 9.76 lbs
4429 g / 43.4 N
26.57 kg / 58.59 lbs
~0 Gs
20 mm 9.92 kg / 21.87 lbs
4 145 Gs
1.49 kg / 3.28 lbs
1488 g / 14.6 N
8.93 kg / 19.68 lbs
~0 Gs
50 mm 0.61 kg / 1.33 lbs
1 024 Gs
0.09 kg / 0.20 lbs
91 g / 0.9 N
0.54 kg / 1.20 lbs
~0 Gs
60 mm 0.29 kg / 0.64 lbs
712 Gs
0.04 kg / 0.10 lbs
44 g / 0.4 N
0.26 kg / 0.58 lbs
~0 Gs
70 mm 0.15 kg / 0.34 lbs
514 Gs
0.02 kg / 0.05 lbs
23 g / 0.2 N
0.14 kg / 0.30 lbs
~0 Gs
80 mm 0.08 kg / 0.19 lbs
383 Gs
0.01 kg / 0.03 lbs
13 g / 0.1 N
0.08 kg / 0.17 lbs
~0 Gs
90 mm 0.05 kg / 0.11 lbs
293 Gs
0.01 kg / 0.02 lbs
7 g / 0.1 N
0.04 kg / 0.10 lbs
~0 Gs
100 mm 0.03 kg / 0.07 lbs
230 Gs
0.00 kg / 0.01 lbs
5 g / 0.0 N
0.03 kg / 0.06 lbs
~0 Gs

Table 7: Safety (HSE) (implants) - warnings
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
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

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

Start from (mm) Speed (km/h) Energy (J) Predicted outcome
10 mm 23.51 km/h
(6.53 m/s)
0.46 J
30 mm 25.12 km/h
(6.98 m/s)
0.52 J
50 mm 25.19 km/h
(7.00 m/s)
0.53 J
100 mm 25.20 km/h
(7.00 m/s)
0.53 J

Table 9: Coating parameters (durability)
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)

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

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

Table 11: Underwater work (magnet fishing)
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: Remember to wipe the magnet thoroughly after removing it from water and apply a protective layer (e.g., oil) to avoid corrosion.

1. Shear force

*Note: On a vertical wall, the magnet holds just a fraction of its nominal pull.

2. Steel thickness impact

*Thin metal sheet (e.g. computer case) significantly weakens the holding force.

3. Heat tolerance

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

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

chart generated for the permeance coefficient Pc (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 Pc (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 Pc 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.

Engineering data and GPSR

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%

Ecology and recycling (GPSR)

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: 030191-2026
Measurement Calculator

Pulling force


Magnetic Induction

Check out also offers

The ring-shaped magnet MP 25x13x8 / N38 is created for permanent mounting, 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 10.49 kg works great as a door latch, speaker holder, or spacer element in devices.
This is a crucial issue when working with model MP 25x13x8 / N38. Neodymium magnets are sintered ceramics, which means they are hard but breakable 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.
Moisture can penetrate micro-cracks in the coating and cause oxidation of the magnet. 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. This product is dedicated for indoor use. For outdoor applications, we recommend choosing rubberized holders or additional protection with varnish.
A screw or bolt with a thread diameter smaller than 13 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.
The presented product is a ring magnet with dimensions Ø25 mm (outer diameter) and height 8 mm. The key parameter here is the lifting capacity amounting to approximately 10.49 kg (force ~102.90 N). The product has a [NiCuNi] coating and is made of NdFeB material. Inner hole dimension: 13 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). We do not offer paired sets with marked poles in this category, but they are easy to match manually.

Advantages and disadvantages of rare earth magnets.

Advantages

Besides their exceptional pulling force, neodymium magnets offer the following advantages:
  • They retain attractive force for almost ten years – the drop is just ~1% (according to analyses),
  • Magnets perfectly protect themselves against loss of magnetization caused by foreign field sources,
  • In other words, due to the aesthetic surface of silver, the element is aesthetically pleasing,
  • They are known for high magnetic induction at the operating surface, making them more effective,
  • Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
  • Considering the ability of accurate forming and customization to unique solutions, magnetic components can be produced in a broad palette of shapes and sizes, which increases their versatility,
  • Versatile presence in modern technologies – they are used in data components, electric motors, medical equipment, also multitasking production systems.
  • Thanks to concentrated force, small magnets offer high operating force, in miniature format,

Limitations

Disadvantages of neodymium magnets:
  • They are fragile upon heavy impacts. To avoid cracks, it is worth protecting magnets in a protective case. Such protection not only protects the magnet but also increases its resistance to damage
  • Neodymium magnets lose their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their power. Therefore, we recommend our special magnets marked [AH], which maintain durability even at temperatures up to 230°C
  • Magnets exposed to a humid environment can rust. Therefore during using outdoors, we recommend using waterproof magnets made of rubber, plastic or other material resistant to moisture
  • We suggest a housing - magnetic mount, due to difficulties in realizing threads inside the magnet and complicated shapes.
  • Potential hazard related to microscopic parts of magnets are risky, if swallowed, which becomes key in the aspect of protecting the youngest. Additionally, tiny parts of these devices can complicate diagnosis medical in case of swallowing.
  • With budget limitations the cost of neodymium magnets can be a barrier,

Pull force analysis

Magnetic strength at its maximum – what it depends on?

The declared magnet strength represents the maximum value, measured under optimal environment, namely:
  • on a base made of structural steel, optimally conducting the magnetic flux
  • whose transverse dimension reaches at least 10 mm
  • with a plane perfectly flat
  • without the slightest air gap between the magnet and steel
  • under axial force vector (90-degree angle)
  • at temperature room level

Magnet lifting force in use – key factors

Please note that the magnet holding will differ influenced by elements below, in order of importance:
  • Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by veneer or dirt) drastically reduces the pulling force, often by half at just 0.5 mm.
  • Force direction – remember that the magnet has greatest strength perpendicularly. Under sliding down, the holding force drops significantly, often to levels of 20-30% of the nominal value.
  • Substrate thickness – to utilize 100% power, the steel must be sufficiently thick. Thin sheet restricts the attraction force (the magnet "punches through" it).
  • Material composition – different alloys attracts identically. Alloy additives worsen the attraction effect.
  • Smoothness – full contact is obtained only on polished steel. Any scratches and bumps reduce the real contact area, weakening the magnet.
  • Thermal environment – heating the magnet causes a temporary drop of induction. Check the thermal limit for a given model.

Lifting capacity was determined using a polished steel plate of optimal thickness (min. 20 mm), under vertically applied force, whereas under shearing force the lifting capacity is smaller. Additionally, even a minimal clearance between the magnet and the plate reduces the load capacity.

Precautions when working with neodymium magnets
Precision electronics

GPS units and smartphones are highly susceptible to magnetism. Close proximity with a strong magnet can ruin the internal compass in your phone.

Serious injuries

Watch your fingers. Two powerful magnets will join immediately with a force of massive weight, crushing anything in their path. Exercise extreme caution!

Metal Allergy

Some people experience a sensitization to nickel, which is the standard coating for neodymium magnets. Extended handling can result in a rash. We strongly advise use safety gloves.

Conscious usage

Before use, read the rules. Sudden snapping can destroy the magnet or hurt your hand. Think ahead.

Operating temperature

Do not overheat. Neodymium magnets are sensitive to heat. If you need operation above 80°C, ask us about HT versions (H, SH, UH).

Do not drill into magnets

Combustion risk: Rare earth powder is highly flammable. Avoid machining magnets in home conditions as this risks ignition.

Health Danger

People with a ICD must keep an large gap from magnets. The magnetism can disrupt the functioning of the life-saving device.

Fragile material

Neodymium magnets are ceramic materials, which means they are very brittle. Impact of two magnets will cause them cracking into shards.

Safe distance

Device Safety: Strong magnets can damage payment cards and delicate electronics (heart implants, hearing aids, mechanical watches).

Do not give to children

Product intended for adults. Tiny parts pose a choking risk, leading to severe trauma. Store away from children and animals.

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