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MP 12x8/4x3 / 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 030395

GTIN/EAN: 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

2.21 kg / 21.72 N

Magnetic Induction

277.09 mT / 2771 Gs

Coating

[NiCuNi] Nickel

1.427 ZŁ 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/EAN	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 ~ ?	2.21 kg / 21.72 N
Magnetic Induction ~ ?	277.09 mT / 2771 Gs
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	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

Physical simulation of the product - data

The following data constitute the outcome of a mathematical analysis. Results rely on models for the material Nd₂Fe₁₄B. Actual performance may differ from theoretical values. Use these calculations as a reference point when designing systems.

Table 1: Static force (force vs distance) - characteristics
MP 12x8/4x3 / N38

Distance (mm)	Induction (Gauss) / mT	Pull Force (kg)	Risk Status
0 mm	2423 Gs 242.3 mT	2.21 kg / 2210.0 g 21.7 N	medium risk
1 mm	2138 Gs 213.8 mT	1.72 kg / 1720.7 g 16.9 N	low risk
2 mm	1786 Gs 178.6 mT	1.20 kg / 1200.5 g 11.8 N	low risk
3 mm	1437 Gs 143.7 mT	0.78 kg / 777.8 g 7.6 N	low risk
5 mm	885 Gs 88.5 mT	0.29 kg / 294.7 g 2.9 N	low risk
10 mm	277 Gs 27.7 mT	0.03 kg / 28.9 g 0.3 N	low risk
15 mm	110 Gs 11.0 mT	0.00 kg / 4.6 g 0.0 N	low risk
20 mm	53 Gs 5.3 mT	0.00 kg / 1.1 g 0.0 N	low risk
30 mm	18 Gs 1.8 mT	0.00 kg / 0.1 g 0.0 N	low risk
50 mm	4 Gs 0.4 mT	0.00 kg / 0.0 g 0.0 N	low risk

Magnetic force weakens significantly with every subsequent millimeter of spacing. Note that even a microscopic distance (e.g., dirt, paint, veneer) significantly reduces the pull force. Neodymiums hold strongest in perfect adhesion; air break weakens the force. Observe how quickly the load capacity drop, when the magnet does not adhere tightly to the steel surface. When designing the arrangement, avoid redundant distances.

Table 2: Shear force (vertical surface)
MP 12x8/4x3 / N38

Distance (mm)	Friction coefficient	Pull Force (kg)
0 mm	Stal (~0.2)	0.44 kg / 442.0 g 4.3 N
1 mm	Stal (~0.2)	0.34 kg / 344.0 g 3.4 N
2 mm	Stal (~0.2)	0.24 kg / 240.0 g 2.4 N
3 mm	Stal (~0.2)	0.16 kg / 156.0 g 1.5 N
5 mm	Stal (~0.2)	0.06 kg / 58.0 g 0.6 N
10 mm	Stal (~0.2)	0.01 kg / 6.0 g 0.1 N
15 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N
20 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N
30 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N
50 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N

The table below defines the theoretical shear load required to cause the downward movement of the magnet downwards on a upright steel wall (assuming standard friction coefficient). This value depends on the distance between the magnet and the surface.

Table 3: Wall mounting (sliding) - vertical pull
MP 12x8/4x3 / N38

Surface type	Friction coefficient / % Mocy	Max load (kg)
Raw steel	µ = 0.3 30% Nominalnej Siły	0.66 kg / 663.0 g 6.5 N
Painted steel (standard)	µ = 0.2 20% Nominalnej Siły	0.44 kg / 442.0 g 4.3 N
Oily/slippery steel	µ = 0.1 10% Nominalnej Siły	0.22 kg / 221.0 g 2.2 N
Magnet with anti-slip rubber	µ = 0.5 50% Nominalnej Siły	1.11 kg / 1105.0 g 10.8 N

When hanging a magnet on a vertical surface (e.g., a car body), it will only hold just approx. 1/5 of nominal attraction strength. Gravitational force and a weak degree of grip mean that holders move down easier than they detach. Planning a vertical fastening? Remember that the sliding force is noticeably lower than the perpendicular breakaway force. On a smooth steel, the element will slide down under a much lighter load. Using a rubber coating can effectively increase the grip.

Table 4: Steel thickness (saturation) - sheet metal selection
MP 12x8/4x3 / N38

Steel thickness (mm)	% power	Real pull force (kg)
0.5 mm	10%	0.22 kg / 221.0 g 2.2 N
1 mm	25%	0.55 kg / 552.5 g 5.4 N
2 mm	50%	1.11 kg / 1105.0 g 10.8 N
5 mm	100%	2.21 kg / 2210.0 g 21.7 N
10 mm	100%	2.21 kg / 2210.0 g 21.7 N

A thin metal plate is incapable of absorb the entire magnetic field, which wastes potential of the holder. If you attach a powerful product to a thin surface, the magnetism will penetrate right through and the holding will be smaller. To achieve 100% of this neodymium's power, you require a sufficiently solid piece of metal. The material oversaturation causes that on thin elements (e.g., thin profiles), the holder shows lower pull force. We advise picking the steel cross-section according to the table below.

Table 5: Thermal resistance (material behavior) - thermal limit
MP 12x8/4x3 / N38

Ambient temp. (°C)	Power loss	Remaining pull	Status
20 °C	0.0%	2.21 kg / 2210.0 g 21.7 N	OK
40 °C	-2.2%	2.16 kg / 2161.4 g 21.2 N	OK
60 °C	-4.4%	2.11 kg / 2112.8 g 20.7 N
80 °C	-6.6%	2.06 kg / 2064.1 g 20.2 N
100 °C	-28.8%	1.57 kg / 1573.5 g 15.4 N

Classic neodymiums lose power above the temperature limit. Protect against heat – high temperature can irreversibly damage this product. As the temperature rises, the magnet's power briefly lowers. Do not use this product close to ovens exceeding its operating temperature limit. Too high temperature will result in permanent loss of magnetism.

*Engineering note: Temperature resistance is determined by both grade, and the Permeance Coefficient Pc. Thin magnets (pancake types) risk losing magnetic properties sooner than long magnets. Warning indicator in the table indicates a risk of irreversible loss for this particular item.

Table 6: Two magnets (attraction) - forces in the system
MP 12x8/4x3 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	3.09 kg / 3092 g 30.3 N 4 010 Gs	N/A
1 mm	2.77 kg / 2774 g 27.2 N 4 589 Gs	2.50 kg / 2496 g 24.5 N ~0 Gs
2 mm	2.41 kg / 2408 g 23.6 N 4 276 Gs	2.17 kg / 2167 g 21.3 N ~0 Gs
3 mm	2.03 kg / 2034 g 20.0 N 3 930 Gs	1.83 kg / 1831 g 18.0 N ~0 Gs
5 mm	1.36 kg / 1362 g 13.4 N 3 216 Gs	1.23 kg / 1226 g 12.0 N ~0 Gs
10 mm	0.41 kg / 412 g 4.0 N 1 770 Gs	0.37 kg / 371 g 3.6 N ~0 Gs
20 mm	0.04 kg / 40 g 0.4 N 554 Gs	0.04 kg / 36 g 0.4 N ~0 Gs
50 mm	0.00 kg / 0 g 0.0 N 58 Gs	0.00 kg / 0 g 0.0 N ~0 Gs

Two strong neodymiums interact from a significantly greater distance than a magnet and steel combination. Such a system of magnet-to-magnet creates a more powerful interaction and a further horizon of performance. Want to build a strong closure? Apply two magnets instead of a neodymium and a striker plate. Be careful that when connecting a pair of magnets, the collision energy is huge. The levitation is a bit weaker than the connection force, but still significant.
*Field value for N-N configuration reaches ~0 Gs at the midpoint of the gap (due to field cancellation).

Table 7: Protective zones (electronics) - precautionary measures
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
Timepiece	20 Gs (2.0 mT)	3.0 cm
Phone / Smartphone	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

Extremely neodym field is a real danger to IT equipment and medical implants. These NdFeB products generate a field that destroys function of sensitive medical devices. Be aware: the invisible magnetic field passes through tissues and glass. Exceptional care must be exercised by people with cochlear implants and drug dispensers. Also at risk are: mechanical watches, remotes, membranes, and displays. Avoid contact with magnetic cards, hard drives, or sensitive navigation tools.

Table 8: Dynamics (kinetic energy) - warning
MP 12x8/4x3 / N38

Start from (mm)	Speed (km/h)	Energy (J)
10 mm	31.79 km/h (8.83 m/s)	0.09 J
30 mm	54.63 km/h (15.17 m/s)	0.26 J
50 mm	70.52 km/h (19.59 m/s)	0.43 J
100 mm	99.73 km/h (27.70 m/s)	0.87 J

NdFeB products are delicate – a violent impact against metal causes immediate chipping. Pay attention to connection velocity – a neodymium left loose becomes dangerous. Impact energy can cause material chips or painful pinches to skin. Always hold the magnet during mounting so it doesn't slam with momentum against the steel surface. A collision at high speed almost guarantees destruction of the neodymium. Wear eye protection when working with powerful specimens.

Table 9: 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)

For outdoor applications, an epoxy coating is required; standard nickel is intended for indoor use. The silver nickel coating also serves an aesthetic function but is not fully waterproof.

Table 10: Construction data (Flux)
MP 12x8/4x3 / N38

Parameter	Value	SI Unit / Description
Magnetic Flux	2 466 Mx	24.7 µWb
P_c Coefficient	0.32	Low (Flat)

Flux value emitted by the pole surface. Key data for generator designers as well as sensors. P_c value determines the working geometry.

Table 11: Physics of underwater searching
MP 12x8/4x3 / N38

Environment	Effective steel pull	Effect
Air (land)	2.21 kg	Standard
Water (riverbed)	2.53 kg (+0.32 kg Buoyancy gain)	+14.5%

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

The magnetic field penetrates through water without any losses. As a result, your magnet will pull a heavier object from the bottom than if you lifted it in the air.

1. Vertical hold

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

2. Steel thickness impact

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

3. Thermal stability

*For standard magnets, the safety limit is 80°C.

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

chart generated for the permeance coefficient P_c (Permeance Coefficient) = 0.32

The chart above illustrates the magnetic characteristics of the material within the second quadrant of the hysteresis loop. 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 specification and ecology

Elemental analysis

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: 030395-2025

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The ring magnet with a hole MP 12x8/4x3 / N38 is created for permanent mounting, where glue might fail or be insufficient. Thanks to the hole (often for a screw), this model enables easy screwing to wood, wall, plastic, or metal. 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. It's a good idea to use a flexible washer 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. If you must use it outside, paint it with anti-corrosion paint after mounting.

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.

It is a magnetic ring with a diameter of 12 mm and thickness 3 mm. The key parameter here is the holding force amounting to approximately 2.21 kg (force ~21.72 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. In the case of connecting two rings, make sure one is turned the right way. When ordering a larger quantity, magnets are usually packed in stacks, where they are already naturally paired.

Pros as well as cons of rare earth magnets.

Pros

In addition to their pulling strength, neodymium magnets provide the following advantages:

They do not lose power, even over around ten years – the drop in lifting capacity is only ~1% (according to tests),
Magnets very well protect themselves against demagnetization caused by foreign field sources,
The use of an elegant finish of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
They feature high magnetic induction at the operating surface, making them more effective,
Made from properly selected components, these magnets show impressive resistance to high heat, enabling them to function (depending on their shape) at temperatures up to 230°C and above...
Thanks to freedom in designing and the ability to modify to specific needs,
Huge importance in future technologies – they are used in computer drives, motor assemblies, advanced medical instruments, as well as industrial machines.
Thanks to concentrated force, small magnets offer high operating force, with minimal size,

Disadvantages

Characteristics of disadvantages of neodymium magnets: tips and applications.

To avoid cracks upon strong impacts, we suggest using special steel holders. Such a solution protects the magnet and simultaneously increases its durability.
We warn that neodymium magnets can reduce their strength at high temperatures. To prevent this, we suggest our specialized [AH] magnets, which work effectively even at 230°C.
They oxidize in a humid environment - during use outdoors we advise using waterproof magnets e.g. in rubber, plastic
We recommend cover - magnetic mechanism, due to difficulties in producing nuts inside the magnet and complicated forms.
Possible danger resulting from small fragments of magnets pose a threat, if swallowed, which becomes key in the context of child safety. Additionally, tiny parts of these magnets can disrupt the diagnostic process medical in case of swallowing.
High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which hinders application in large quantities

Pull force analysis

Maximum lifting capacity of the magnet – what contributes to it?

Breakaway force is the result of a measurement for optimal configuration, assuming:

on a base made of structural steel, effectively closing the magnetic field
with a thickness of at least 10 mm
characterized by even structure
with zero gap (no paint)
during pulling in a direction vertical to the mounting surface
at standard ambient temperature

What influences lifting capacity in practice

Holding efficiency is affected by specific conditions, including (from most important):

Clearance – existence of foreign body (paint, tape, air) acts as an insulator, which reduces power steeply (even by 50% at 0.5 mm).
Pull-off angle – note that the magnet holds strongest perpendicularly. Under sliding down, the capacity drops drastically, often to levels of 20-30% of the maximum value.
Metal thickness – thin material does not allow full use of the magnet. Part of the magnetic field penetrates through instead of converting into lifting capacity.
Metal type – different alloys reacts the same. High carbon content worsen the interaction with the magnet.
Surface condition – smooth surfaces ensure maximum contact, which improves field saturation. Rough surfaces reduce efficiency.
Thermal environment – temperature increase results in weakening of induction. It is worth remembering the maximum operating temperature for a given model.

Holding force was tested on the plate surface of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the lifting capacity is smaller. Additionally, even a small distance between the magnet’s surface and the plate reduces the lifting capacity.

Safe handling of NdFeB magnets

Skin irritation risks

Nickel alert: The nickel-copper-nickel coating consists of nickel. If redness appears, cease handling magnets and wear gloves.

Phone sensors

An intense magnetic field interferes with the operation of compasses in smartphones and GPS navigation. Keep magnets near a smartphone to prevent damaging the sensors.

Electronic hazard

Do not bring magnets close to a wallet, laptop, or TV. The magnetic field can destroy these devices and erase data from cards.

Do not underestimate power

Handle magnets consciously. Their huge power can shock even experienced users. Be vigilant and do not underestimate their power.

Material brittleness

Protect your eyes. Magnets can fracture upon uncontrolled impact, ejecting shards into the air. Eye protection is mandatory.

Medical interference

Medical warning: Strong magnets can turn off heart devices and defibrillators. Do not approach if you have electronic implants.

Dust explosion hazard

Powder generated during machining of magnets is flammable. Do not drill into magnets without proper cooling and knowledge.

Do not give to children

Adult use only. Small elements pose a choking risk, leading to serious injuries. Store out of reach of kids and pets.

Maximum temperature

Avoid heat. NdFeB magnets are sensitive to heat. If you need resistance above 80°C, ask us about HT versions (H, SH, UH).

Hand protection

Risk of injury: The pulling power is so great that it can result in blood blisters, crushing, and broken bones. Use thick gloves.

Security! Looking for details? Read our article: Are neodymium magnets dangerous?

MP 12x8/4x3 / N38 - ring magnet

Looking for a better price?

MP 12x8/4x3 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Physical simulation of the product - data

1. Vertical hold

2. Steel thickness impact

3. Thermal stability

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

Elemental analysis

Sustainability

Magnet pull force

Magnetic Induction

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KM HF - 34,5 kg - magnetic bracket

Pros as well as cons of rare earth magnets.

Pros

Disadvantages

Pull force analysis

Maximum lifting capacity of the magnet – what contributes to it?

What influences lifting capacity in practice

Skin irritation risks

Phone sensors

Electronic hazard

Do not underestimate power

Material brittleness

Medical interference

Dust explosion hazard

Do not give to children

Maximum temperature

Hand protection

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C