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MP 12x8/4x3 / N38 - ring magnet

ring magnet

Catalog no 030395

GTIN: 5906301812326

5.00

Diameter

12 mm [±0,1 mm]

internal diameter Ø

8/4 mm [±0,1 mm]

Height

3 mm [±0,1 mm]

Weight

2.26 g

Magnetization Direction

↑ axial

Load capacity

1.49 kg / 14.65 N

Magnetic Induction

237.19 mT

Coating

[NiCuNi] Nickel

1.427 with VAT / pcs + price for transport

1.160 ZŁ net + 23% VAT / pcs

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MP 12x8/4x3 / N38 - ring magnet

Specification / characteristics MP 12x8/4x3 / N38 - ring magnet

properties
properties values
Cat. no. 030395
GTIN 5906301812326
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 12 mm [±0,1 mm]
internal diameter Ø 8/4 mm [±0,1 mm]
Height 3 mm [±0,1 mm]
Weight 2.26 g
Magnetization Direction ↑ axial
Load capacity ~ ? 1.49 kg / 14.65 N
Magnetic Induction ~ ? 237.19 mT
Coating [NiCuNi] Nickel
Manufacturing Tolerance ±0.1 mm

Magnetic properties of material N38

Specification / characteristics MP 12x8/4x3 / 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

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

Technical analysis of the assembly - technical parameters

The following information are the outcome of a mathematical calculation. Values are based on models for the class NdFeB. Real-world conditions might slightly deviate from the simulation results. Use these data as a supplementary guide for designers.

Table 1: Static force (pull vs gap) - characteristics
MP 12x8/4x3 / N38
Distance (mm) Induction (Gauss) / mT Pull Force (kg) Risk Status
0 mm 2423 Gs
242.3 mT
1.49 kg / 1490.0 g
14.6 N
safe
1 mm 2138 Gs
213.8 mT
1.16 kg / 1160.1 g
11.4 N
safe
2 mm 1786 Gs
178.6 mT
0.81 kg / 809.4 g
7.9 N
safe
5 mm 885 Gs
88.5 mT
0.20 kg / 198.7 g
1.9 N
safe
10 mm 277 Gs
27.7 mT
0.02 kg / 19.5 g
0.2 N
safe
15 mm 110 Gs
11.0 mT
0.00 kg / 3.1 g
0.0 N
safe
20 mm 53 Gs
5.3 mT
0.00 kg / 0.7 g
0.0 N
safe
30 mm 18 Gs
1.8 mT
0.00 kg / 0.1 g
0.0 N
safe
50 mm 4 Gs
0.4 mT
0.00 kg / 0.0 g
0.0 N
safe
Table 2: Wall mounting (shearing) - vertical pull
MP 12x8/4x3 / N38
Surface type Friction coefficient / % Mocy Max load (kg)
Raw steel
µ = 0.3 30% Nominalnej Siły
0.45 kg / 447.0 g
4.4 N
Painted steel (standard)
µ = 0.2 20% Nominalnej Siły
0.30 kg / 298.0 g
2.9 N
Oily/slippery steel
µ = 0.1 10% Nominalnej Siły
0.15 kg / 149.0 g
1.5 N
Magnet with anti-slip rubber
µ = 0.5 50% Nominalnej Siły
0.75 kg / 745.0 g
7.3 N
Table 3: Material efficiency (saturation) - power losses
MP 12x8/4x3 / N38
Steel thickness (mm) % power Real pull force (kg)
0.5 mm
10%
0.15 kg / 149.0 g
1.5 N
1 mm
25%
0.37 kg / 372.5 g
3.7 N
2 mm
50%
0.75 kg / 745.0 g
7.3 N
5 mm
100%
1.49 kg / 1490.0 g
14.6 N
10 mm
100%
1.49 kg / 1490.0 g
14.6 N
Table 4: Thermal resistance (material behavior) - power drop
MP 12x8/4x3 / N38
Ambient temp. (°C) Power loss Remaining pull Status
20 °C 0.0% 1.49 kg / 1490.0 g
14.6 N
OK
40 °C -2.2% 1.46 kg / 1457.2 g
14.3 N
OK
60 °C -4.4% 1.42 kg / 1424.4 g
14.0 N
OK
80 °C -6.6% 1.39 kg / 1391.7 g
13.7 N
100 °C -28.8% 1.06 kg / 1060.9 g
10.4 N
Table 5: Two magnets (repulsion) - forces in the system
MP 12x8/4x3 / N38
Gap (mm) Attraction (kg) (N-S) Repulsion (kg) (N-N)
0 mm 2.24 kg / 2235.0 g
21.9 N
N/A
2 mm 1.22 kg / 1215.0 g
11.9 N
1.13 kg / 1134.0 g
11.1 N
5 mm 0.30 kg / 300.0 g
2.9 N
0.28 kg / 280.0 g
2.7 N
10 mm 0.03 kg / 30.0 g
0.3 N
0.03 kg / 28.0 g
0.3 N
20 mm 0.00 kg / 0.0 g
0.0 N
0.00 kg / 0.0 g
0.0 N
50 mm 0.00 kg / 0.0 g
0.0 N
0.00 kg / 0.0 g
0.0 N
Table 6: Protective zones (electronics) - warnings
MP 12x8/4x3 / N38
Object / Device Limit (Gauss) / mT Safe distance
Pacemaker 5 Gs (0.5 mT) 5.0 cm
Hearing aid 10 Gs (1.0 mT) 4.0 cm
Mechanical watch 20 Gs (2.0 mT) 3.0 cm
Mobile device 40 Gs (4.0 mT) 2.5 cm
Car key 50 Gs (5.0 mT) 2.5 cm
Payment card 400 Gs (40.0 mT) 1.0 cm
HDD hard drive 600 Gs (60.0 mT) 1.0 cm
Table 7: Impact energy (cracking risk) - warning
MP 12x8/4x3 / N38
Start from (mm) Speed (km/h) Energy (J) Predicted outcome
10 mm 26.11 km/h
(7.25 m/s)
0.06 J
30 mm 44.85 km/h
(12.46 m/s)
0.18 J
50 mm 57.90 km/h
(16.08 m/s)
0.29 J
100 mm 81.89 km/h
(22.75 m/s)
0.58 J
Table 8: Coating parameters (durability)
MP 12x8/4x3 / 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 9: Underwater work (magnet fishing)
MP 12x8/4x3 / N38
Environment Effective steel pull Effect
Air (land) 1.49 kg Standard
Water (riverbed) 1.71 kg
(+0.22 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.

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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. One turn too many can destroy the magnet, so do it slowly. The flat screw head should evenly press the magnet. 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 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 magnets in hermetic housing or additional protection with varnish.
A screw or bolt with a thread diameter smaller than 8/4 mm fits this model. 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. Always check that the screw head is not larger than the outer diameter of the magnet (12 mm), so it doesn't protrude beyond the outline.
This model is characterized by dimensions Ø12x3 mm and a weight of 2.26 g. The key parameter here is the holding force amounting to approximately 1.49 kg (force ~14.65 N). The product has a [NiCuNi] coating and is made of NdFeB material. Inner hole dimension: 8/4 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 as well as cons of neodymium magnets.

Besides their exceptional magnetic power, neodymium magnets offer the following advantages:

  • They have stable power, and over more than 10 years their attraction force decreases symbolically – ~1% (according to theory),
  • They feature excellent resistance to magnetic field loss when exposed to external fields,
  • Thanks to the shiny finish, the surface of nickel, gold-plated, or silver gives an elegant appearance,
  • They are known for high magnetic induction at the operating surface, which affects their effectiveness,
  • Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their form) at temperatures up to 230°C and above...
  • In view of the possibility of precise shaping and adaptation to custom solutions, neodymium magnets can be modeled in a variety of forms and dimensions, which expands the range of possible applications,
  • Huge importance in modern technologies – they serve a role in data components, brushless drives, medical devices, also industrial machines.
  • Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in small dimensions, which enables their usage in small systems

Disadvantages of neodymium magnets:

  • To avoid cracks upon strong impacts, we suggest using special steel housings. Such a solution protects the magnet and simultaneously increases its durability.
  • Neodymium magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent drop of strength (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 extremely resistant to heat
  • They rust in a humid environment. For use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
  • Due to limitations in realizing nuts and complex shapes in magnets, we propose using casing - magnetic mechanism.
  • Possible danger related to microscopic parts of magnets pose a threat, when accidentally swallowed, which gains importance in the context of child safety. Furthermore, small elements of these magnets are able to be problematic in diagnostics medical in case of swallowing.
  • With large orders the cost of neodymium magnets is a challenge,

Maximum lifting capacity of the magnetwhat contributes to it?

Breakaway force was defined for ideal contact conditions, taking into account:

  • using a base made of low-carbon steel, serving as a ideal flux conductor
  • possessing a thickness of min. 10 mm to ensure full flux closure
  • characterized by even structure
  • without any insulating layer between the magnet and steel
  • during pulling in a direction perpendicular to the plane
  • in stable room temperature

Practical lifting capacity: influencing factors

Effective lifting capacity impacted by specific conditions, including (from priority):

  • Clearance – the presence of foreign body (paint, dirt, air) interrupts the magnetic circuit, which lowers capacity steeply (even by 50% at 0.5 mm).
  • Pull-off angle – note that the magnet holds strongest perpendicularly. Under shear forces, the holding force drops significantly, often to levels of 20-30% of the maximum value.
  • Base massiveness – too thin steel causes magnetic saturation, causing part of the power to be escaped to the other side.
  • Steel grade – ideal substrate is pure iron steel. Stainless steels may attract less.
  • Surface finish – full contact is possible only on polished steel. Any scratches and bumps create air cushions, weakening the magnet.
  • Heat – NdFeB sinters have a negative temperature coefficient. At higher temperatures they lose power, and at low temperatures gain strength (up to a certain limit).

* Lifting capacity testing was conducted on a smooth plate of optimal thickness, under a perpendicular pulling force, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. Additionally, even a minimal clearance {between} the magnet’s surface and the plate reduces the lifting capacity.

Safety rules for work with NdFeB magnets

Combustion hazard

Powder created during cutting of magnets is self-igniting. Do not drill into magnets without proper cooling and knowledge.

Health Danger

Health Alert: Neodymium magnets can deactivate heart devices and defibrillators. Do not approach if you have electronic implants.

Magnet fragility

Despite the nickel coating, the material is brittle and not impact-resistant. Do not hit, as the magnet may crumble into sharp, dangerous pieces.

GPS and phone interference

Navigation devices and smartphones are extremely susceptible to magnetic fields. Close proximity with a powerful NdFeB magnet can permanently damage the internal compass in your phone.

Respect the power

Handle with care. Rare earth magnets act from a distance and snap with massive power, often faster than you can react.

Swallowing risk

NdFeB magnets are not suitable for play. Swallowing several magnets may result in them connecting inside the digestive tract, which constitutes a severe health hazard and requires immediate surgery.

Serious injuries

Watch your fingers. Two powerful magnets will join instantly with a force of massive weight, crushing everything in their path. Be careful!

Maximum temperature

Regular neodymium magnets (N-type) undergo demagnetization when the temperature goes above 80°C. The loss of strength is permanent.

Data carriers

Do not bring magnets close to a purse, laptop, or TV. The magnetic field can destroy these devices and wipe information from cards.

Nickel allergy

Warning for allergy sufferers: The nickel-copper-nickel coating consists of nickel. If an allergic reaction happens, cease handling magnets and wear gloves.

Security!

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

Dhit sp. z o.o.

e-mail: bok@dhit.pl

tel: +48 888 99 98 98