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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: 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

0.28 mT / 3 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	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 ~ ?	0.28 mT / 3 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	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

Engineering analysis of the product - technical parameters

The following data represent the outcome of a physical calculation. Values were calculated on algorithms for the class NdFeB. Actual conditions may differ. Use these data as a preliminary roadmap 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	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	safe
2 mm	1786 Gs 178.6 mT	1.20 kg / 1200.5 g 11.8 N	safe
3 mm	1437 Gs 143.7 mT	0.78 kg / 777.8 g 7.6 N	safe
5 mm	885 Gs 88.5 mT	0.29 kg / 294.7 g 2.9 N	safe
10 mm	277 Gs 27.7 mT	0.03 kg / 28.9 g 0.3 N	safe
15 mm	110 Gs 11.0 mT	0.00 kg / 4.6 g 0.0 N	safe
20 mm	53 Gs 5.3 mT	0.00 kg / 1.1 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

Grip strength weakens significantly per each millimeter of distance. Keep in mind that even the smallest gap (e.g., contamination, paint, veneer) strongly weakens the grip. Neodymiums work optimally during direct contact; distance drastically cuts the power. Notice how flashily the parameters plummet, when the magnet does not touch directly to the steel surface. When planning the assembly, discard additional spacers.

Table 2: Slippage 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 following data presents the theoretical weight limit required to start the slippage of the magnet vertically against a upright steel wall (assuming standard friction). The holding force is relative to the separation distance between the magnet and the metal.

Table 3: Wall mounting (sliding) - behavior on slippery surfaces
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 holder on a vertical surface (e.g., a car body), it will only hold just about 20%-30% of nominal attraction strength. Gravity and a weak degree of grip cause that magnets move down faster than they pull off. Planning a hanger? Note that the sliding force is much weaker than the maximum static pull force. On a smooth steel, the element will slide down under a significantly smaller weight. Utilizing a rubberized coating can significantly raise the stability.

Table 4: Material efficiency (substrate influence) - 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 sheet cannot take in the full magnetic flux, which wastes potential of the holder. If you install a neodymium to a weak sheet, the field will pass right through and the attraction force will be weaker. To achieve the maximum of this neodymium's potential, you need a suitably thick element of steel. The saturation phenomenon means that on sheet metal structures (e.g., car bodies), the product shows lower pull force. We suggest choosing the steel cross-section according to the table below.

Table 5: Thermal resistance (stability) - power drop
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	OK
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 parameters after exceeding the maximum temperature. Protect against heat – high temperature can irreversibly damage this product. With every degree above norm, the magnet's capacity temporarily drops. Do not use this magnet near heat sources higher than its safe range. Too high temperature will lead to irreversible degradation of magnetism.

Table 6: Magnet-Magnet interaction (repulsion) - forces in the system
MP 12x8/4x3 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	3.32 kg / 3315.0 g 32.5 N	N/A
2 mm	1.80 kg / 1800.0 g 17.7 N	1.68 kg / 1680.0 g 16.5 N
5 mm	0.43 kg / 435.0 g 4.3 N	0.41 kg / 406.0 g 4.0 N
10 mm	0.05 kg / 45.0 g 0.4 N	0.04 kg / 42.0 g 0.4 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

Two magnets interact from a significantly greater distance than a magnet and steel setup. Such a system of two magnets generates a stronger field and a further horizon of operation. Planning to create a strong closure? Apply two magnets instead of one magnet and a steel. Remember that when attracting two neodymiums, the impact force is huge. The levitation is marginally weaker than the connection force, but still impressive.

Table 7: Hazards (implants) - 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
Mobile device	40 Gs (4.0 mT)	2.5 cm
Remote	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

A strong magnetic field is a real danger to electronic devices as well as pacemakers. These NdFeB products produce a flux that prevents correct functioning of sensitive medical devices. Remember: the unseen radiation passes through tissues and plastic. Increased vigilance must be taken by people with hearing aids and insulin pumps. Also at risk are: automatic timepieces, car keys, speakers, and screens. Avoid contact with magnetic cards, hard drives, or precise measuring instruments.

Table 8: Collisions (kinetic energy) - collision effects
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

Neodymium magnets are prone to chipping – a collision with steel causes immediate chipping. Watch the impact speed – a magnet released freely becomes dangerous. Impact energy can destroy the magnet or injury to skin. Be sure to control the product during mounting so it doesn't hit with great force against the metal. A collision at high speed almost guarantees destruction of the neodymium. Wear eye protection when handling with large magnets.

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. Improper coating selection is the most common cause of magnet failure over time.

Table 10: Submerged application
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. However, remember the water resistance when pulling the rope quickly.

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The ring magnet with a hole MP 12x8/4x3 / 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 2.21 kg works great as a cabinet closure, speaker holder, or mounting element in devices.

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.

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 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 (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 pulling force of this model is an impressive 2.21 kg, which translates to 21.72 N in newtons. The product has a [NiCuNi] coating and is made of NdFeB material. Inner hole dimension: 8/4 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 as well as cons of neodymium magnets.

Besides their high retention, neodymium magnets are valued for these benefits:

They virtually do not lose strength, because even after ten years the decline in efficiency is only ~1% (in laboratory conditions),
They are extremely resistant to demagnetization induced by presence of other magnetic fields,
The use of an metallic layer of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
Magnets are characterized by maximum magnetic induction on the active area,
Neodymium magnets are characterized by extremely high magnetic induction on the magnet surface and are able to act (depending on the form) even at a temperature of 230°C or more...
Thanks to versatility in constructing and the capacity to customize to individual projects,
Universal use in modern industrial fields – they are commonly used in computer drives, drive modules, precision medical tools, as well as modern systems.
Thanks to efficiency per cm³, small magnets offer high operating force, with minimal size,

Problematic aspects of neodymium magnets: application proposals

To avoid cracks upon strong impacts, we suggest using special steel holders. Such a solution protects the magnet and simultaneously improves its durability.
NdFeB magnets demagnetize when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of power (a factor is the shape as well as dimensions of the magnet). We offer magnets specially adapted to work at temperatures up to 230°C marked [AH], which are very resistant to heat
When exposed to humidity, magnets start to rust. For applications outside, it is recommended to use protective magnets, such as magnets in rubber or plastics, which secure oxidation as well as corrosion.
Due to limitations in producing nuts and complicated shapes in magnets, we recommend using a housing - magnetic mount.
Health risk to health – tiny shards of magnets can be dangerous, in case of ingestion, which gains importance in the aspect of protecting the youngest. Furthermore, small components of these magnets can be problematic in diagnostics medical after entering the body.
Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Breakaway strength of the magnet in ideal conditions – what contributes to it?

The lifting capacity listed is a theoretical maximum value conducted under specific, ideal conditions:

on a base made of mild steel, optimally conducting the magnetic field
possessing a thickness of at least 10 mm to avoid saturation
with a plane cleaned and smooth
without the slightest air gap between the magnet and steel
during pulling in a direction vertical to the plane
at room temperature

Practical aspects of lifting capacity – factors

It is worth knowing that the working load may be lower influenced by the following factors, starting with the most relevant:

Air gap (between the magnet and the plate), because even a very small distance (e.g. 0.5 mm) can cause a drastic drop in force by up to 50% (this also applies to paint, corrosion or debris).
Force direction – catalog parameter refers to detachment vertically. When slipping, the magnet holds significantly lower power (typically approx. 20-30% of maximum force).
Metal thickness – thin material does not allow full use of the magnet. Magnetic flux passes through the material instead of converting into lifting capacity.
Steel grade – the best choice is high-permeability steel. Hardened steels may generate lower lifting capacity.
Surface structure – the smoother and more polished the surface, the larger the contact zone and higher the lifting capacity. Unevenness creates an air distance.
Thermal environment – heating the magnet results in weakening of force. It is worth remembering the thermal limit for a given model.

* Lifting capacity was assessed with the use of a smooth steel plate of optimal thickness (min. 20 mm), under vertically applied force, in contrast under shearing force the lifting capacity is smaller. In addition, even a slight gap {between} the magnet’s surface and the plate reduces the load capacity.

H&S for magnets

Risk of cracking

NdFeB magnets are sintered ceramics, meaning they are very brittle. Collision of two magnets leads to them shattering into small pieces.

Finger safety

Big blocks can break fingers in a fraction of a second. Do not place your hand betwixt two strong magnets.

Danger to pacemakers

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

Precision electronics

A powerful magnetic field negatively affects the functioning of magnetometers in phones and navigation systems. Keep magnets near a smartphone to avoid breaking the sensors.

Warning for allergy sufferers

Studies show that the nickel plating (the usual finish) is a strong allergen. For allergy sufferers, prevent touching magnets with bare hands or opt for versions in plastic housing.

Caution required

Before starting, read the rules. Sudden snapping can destroy the magnet or hurt your hand. Be predictive.

Choking Hazard

These products are not toys. Accidental ingestion of several magnets can lead to them connecting inside the digestive tract, which constitutes a critical condition and requires immediate surgery.

Operating temperature

Control the heat. Heating the magnet to high heat will ruin its properties and strength.

Keep away from computers

Equipment safety: Strong magnets can ruin data carriers and delicate electronics (heart implants, hearing aids, timepieces).

Combustion hazard

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

Attention!

Details about hazards in the article: Magnet Safety Guide.

MP 12x8/4x3 / N38 - ring magnet

MP 12x8/4x3 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Engineering analysis of the product - technical parameters

Other products

MP 10x6x4 / N38 - ring magnet

MW 45x25 / N38 - cylindrical magnet

RM R7 SUPER - 13000 Gs / N52 - magnetic distributor

MW 10x5 / N38 - cylindrical magnet

Pros as well as cons of neodymium magnets.

Breakaway strength of the magnet in ideal conditions – what contributes to it?

Practical aspects of lifting capacity – factors

H&S for magnets

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C