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MP 15x7/3.5x3 / 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 030182

GTIN/EAN: 5906301811992

5.00

Diameter

15 mm [±0,1 mm]

internal diameter Ø

7/3.5 mm [±0,1 mm]

Height

3 mm [±0,1 mm]

Weight

3.76 g

Magnetization Direction

↑ axial

Load capacity

2.71 kg / 26.61 N

Magnetic Induction

230.16 mT / 2302 Gs

Coating

[NiCuNi] Nickel

1.747 ZŁ with VAT / pcs + price for transport

1.420 ZŁ net + 23% VAT / pcs

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MP 15x7/3.5x3 / N38 - ring magnet

Specification / characteristics MP 15x7/3.5x3 / N38 - ring magnet

properties

properties	values
Cat. no.	030182
GTIN/EAN	5906301811992
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	15 mm [±0,1 mm]
internal diameter Ø	7/3.5 mm [±0,1 mm]
Height	3 mm [±0,1 mm]
Weight	3.76 g
Magnetization Direction	↑ axial
Load capacity ~ ?	2.71 kg / 26.61 N
Magnetic Induction ~ ?	230.16 mT / 2302 Gs
Coating	[NiCuNi] Nickel
Manufacturing Tolerance	±0.1 mm

Magnetic properties of material N38

Specification / characteristics MP 15x7/3.5x3 / 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 analysis of the assembly - technical parameters

The following data constitute the direct effect of a engineering analysis. Results were calculated on models for the class Nd₂Fe₁₄B. Actual conditions might slightly differ from theoretical values. Treat these data as a reference point during assembly planning.

Table 1: Static pull force (force vs distance) - interaction chart
MP 15x7/3.5x3 / N38

Distance (mm)	Induction (Gauss) / mT	Pull Force (kg)	Risk Status
0 mm	1995 Gs 199.5 mT	2.71 kg / 2710.0 g 26.6 N	warning
1 mm	1833 Gs 183.3 mT	2.29 kg / 2289.1 g 22.5 N	warning
2 mm	1618 Gs 161.8 mT	1.78 kg / 1784.1 g 17.5 N	weak grip
3 mm	1385 Gs 138.5 mT	1.31 kg / 1307.5 g 12.8 N	weak grip
5 mm	959 Gs 95.9 mT	0.63 kg / 627.1 g 6.2 N	weak grip
10 mm	362 Gs 36.2 mT	0.09 kg / 89.3 g 0.9 N	weak grip
15 mm	156 Gs 15.6 mT	0.02 kg / 16.5 g 0.2 N	weak grip
20 mm	78 Gs 7.8 mT	0.00 kg / 4.1 g 0.0 N	weak grip
30 mm	27 Gs 2.7 mT	0.00 kg / 0.5 g 0.0 N	weak grip
50 mm	6 Gs 0.6 mT	0.00 kg / 0.0 g 0.0 N	weak grip

Magnetic force weakens sharply with every mm of distance. Keep in mind that even the smallest gap (e.g., contamination, varnish, dust) strongly diminishes the holding power. Neodymiums operate most effectively in perfect adhesion; air break drastically cuts the power. Notice how flashily the load capacity drop, when the product does not adhere flatly to the steel surface. When designing the mounting, discard redundant distances.

Table 2: Sliding load (vertical surface)
MP 15x7/3.5x3 / N38

Distance (mm)	Friction coefficient	Pull Force (kg)
0 mm	Stal (~0.2)	0.54 kg / 542.0 g 5.3 N
1 mm	Stal (~0.2)	0.46 kg / 458.0 g 4.5 N
2 mm	Stal (~0.2)	0.36 kg / 356.0 g 3.5 N
3 mm	Stal (~0.2)	0.26 kg / 262.0 g 2.6 N
5 mm	Stal (~0.2)	0.13 kg / 126.0 g 1.2 N
10 mm	Stal (~0.2)	0.02 kg / 18.0 g 0.2 N
15 mm	Stal (~0.2)	0.00 kg / 4.0 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 indicates the estimated holding capacity required to start the sliding of the magnet downwards along a upright steel wall (considering standard friction). The holding force depends on the separation distance between the magnet and the metal.

Table 3: Vertical assembly (shearing) - vertical pull
MP 15x7/3.5x3 / N38

Surface type	Friction coefficient / % Mocy	Max load (kg)
Raw steel	µ = 0.3 30% Nominalnej Siły	0.81 kg / 813.0 g 8.0 N
Painted steel (standard)	µ = 0.2 20% Nominalnej Siły	0.54 kg / 542.0 g 5.3 N
Oily/slippery steel	µ = 0.1 10% Nominalnej Siły	0.27 kg / 271.0 g 2.7 N
Magnet with anti-slip rubber	µ = 0.5 50% Nominalnej Siły	1.36 kg / 1355.0 g 13.3 N

When mounting a holder on a vertical surface (e.g., a car body), it will maintain only about 1/5 of its nominal power. Gravitational force as well as a weak degree of grip influence the fact that products move down faster than they pull off. Want to create a hanger? Consider that the shear force is significantly lower than the perpendicular breakaway force. On a smooth steel, the magnet will slide down under a much lighter load. Using a rubber layer can effectively raise the stability.

Table 4: Steel thickness (substrate influence) - power losses
MP 15x7/3.5x3 / N38

Steel thickness (mm)	% power	Real pull force (kg)
0.5 mm	10%	0.27 kg / 271.0 g 2.7 N
1 mm	25%	0.68 kg / 677.5 g 6.6 N
2 mm	50%	1.36 kg / 1355.0 g 13.3 N
5 mm	100%	2.71 kg / 2710.0 g 26.6 N
10 mm	100%	2.71 kg / 2710.0 g 26.6 N

A thin metal plate is incapable of absorb the full magnetic flux, which squanders power of the magnet. Should you mount a strong magnet to a thin surface, the flux will penetrate right through and the holding will be smaller. To squeeze full efficiency of this neodymium's power, you require a sufficiently solid element of metal. The saturation effect causes that on delicate walls (e.g., thin profiles), the holder holds weaker. We recommend selecting the steel thickness according to the table below.

Table 5: Thermal stability (material behavior) - thermal limit
MP 15x7/3.5x3 / N38

Ambient temp. (°C)	Power loss	Remaining pull	Status
20 °C	0.0%	2.71 kg / 2710.0 g 26.6 N	OK
40 °C	-2.2%	2.65 kg / 2650.4 g 26.0 N	OK
60 °C	-4.4%	2.59 kg / 2590.8 g 25.4 N
80 °C	-6.6%	2.53 kg / 2531.1 g 24.8 N
100 °C	-28.8%	1.93 kg / 1929.5 g 18.9 N

Classic neodymiums lose parameters past the thermal threshold. Watch out for overheating – high temperature can irreversibly damage this product. As the temperature rises, the neodymium's capacity briefly lowers. Refrain from using this product near heat sources higher than its operating temperature limit. Ignoring the limit will lead to destruction of magnetic properties.

*Engineering note: Thermal stability depends not only on the material grade, and the Permeance Coefficient Pc. Flat magnets (low Pc) risk losing magnetic properties sooner compared to rod magnets. The danger warning in the table points to a risk of irreversible loss for this particular item.

Table 6: Magnet-Magnet interaction (repulsion) - field collision
MP 15x7/3.5x3 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	3.48 kg / 3483 g 34.2 N 3 483 Gs	N/A
1 mm	3.24 kg / 3239 g 31.8 N 3 846 Gs	2.91 kg / 2915 g 28.6 N ~0 Gs
2 mm	2.94 kg / 2942 g 28.9 N 3 666 Gs	2.65 kg / 2648 g 26.0 N ~0 Gs
3 mm	2.62 kg / 2621 g 25.7 N 3 460 Gs	2.36 kg / 2359 g 23.1 N ~0 Gs
5 mm	1.98 kg / 1976 g 19.4 N 3 004 Gs	1.78 kg / 1778 g 17.4 N ~0 Gs
10 mm	0.81 kg / 806 g 7.9 N 1 919 Gs	0.73 kg / 725 g 7.1 N ~0 Gs
20 mm	0.11 kg / 115 g 1.1 N 724 Gs	0.10 kg / 103 g 1.0 N ~0 Gs
50 mm	0.00 kg / 2 g 0.0 N 88 Gs	0.00 kg / 0 g 0.0 N ~0 Gs

Two strong neodymiums attract each other from a much further distance than a magnet and sheet setup. The setup of magnet-to-magnet generates a stronger field and a further horizon of performance. Planning to create a strong closure? Utilize two neodymiums instead of a neodymium and a striker plate. Exercise caution that when connecting a pair of magnets, the pinch force is massive. The levitation is a bit weaker than the attraction, but still significant.
*Flux density for N-N configuration is approximately ~0 Gs at the midpoint of the gap (caused by magnetic field nullification).

Table 7: Safety (HSE) (implants) - precautionary measures
MP 15x7/3.5x3 / N38

Object / Device	Limit (Gauss) / mT	Safe distance
Pacemaker	5 Gs (0.5 mT)	5.5 cm
Hearing aid	10 Gs (1.0 mT)	4.5 cm
Mechanical watch	20 Gs (2.0 mT)	3.5 cm
Phone / Smartphone	40 Gs (4.0 mT)	3.0 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

A strong magnetic field poses a serious hazard to electronics as well as pacemakers. These NdFeB products generate a flux that destroys function of sensitive medical devices. Remember: the unseen radiation penetrates the body and glass. Exceptional care must be exercised by people with hearing aids and insulin pumps. The risk also applies to: mechanical watches, car keys, membranes, and screens. Do not bring the product near payment cards, hard drives, or sensitive navigation tools.

Table 8: Dynamics (kinetic energy) - warning
MP 15x7/3.5x3 / N38

Start from (mm)	Speed (km/h)	Energy (J)
10 mm	27.63 km/h (7.67 m/s)	0.11 J
30 mm	46.90 km/h (13.03 m/s)	0.32 J
50 mm	60.54 km/h (16.82 m/s)	0.53 J
100 mm	85.62 km/h (23.78 m/s)	1.06 J

Magnetic elements are prone to chipping – a violent impact against metal causes immediate chipping. Control the attraction moment – a magnet released freely speeds with massive force. Impact energy can cause material chips or dangerous crushing to skin. Hold the magnet firmly during installation so it doesn't hit with great force against the metal. A collision at high speed means shattering of the magnet. Wear safety glasses when playing with powerful specimens.

Table 9: Surface protection spec
MP 15x7/3.5x3 / 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 15x7/3.5x3 / N38

Parameter	Value	SI Unit / Description
Magnetic Flux	3 461 Mx	34.6 µWb
P_c Coefficient	0.26	Low (Flat)

Total magnetic flux passing through the magnet pole. Key data in coil applications as well as sensors. P_c value defines the working geometry.

Table 11: Physics of underwater searching
MP 15x7/3.5x3 / N38

Environment	Effective steel pull	Effect
Air (land)	2.71 kg	Standard
Water (riverbed)	3.10 kg (+0.39 kg Buoyancy gain)	+14.5%

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

Contrary to myths, water does not block the magnetic field. Buoyancy helps in lifting finds.

1. Wall mount (shear)

*Warning: On a vertical wall, the magnet holds just a fraction of its perpendicular strength.

2. Steel thickness impact

*Thin steel (e.g. 0.5mm PC case) significantly weakens the holding force.

3. Power loss vs temp

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

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

chart generated for the permeance coefficient P_c (Permeance Coefficient) = 0.26

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 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%

Environmental data

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: 030182-2025

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The ring-shaped magnet MP 15x7/3.5x3 / 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 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 does not ensure full waterproofing. Damage to the protective layer during assembly is the most common cause of rusting. 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 7/3.5 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.

This model is characterized by dimensions Ø15x3 mm and a weight of 3.76 g. The key parameter here is the holding force amounting to approximately 2.71 kg (force ~26.61 N). The product has a [NiCuNi] coating and is made of NdFeB material. Inner hole dimension: 7/3.5 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 neodymium magnets.

Pros

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

They virtually do not lose power, because even after 10 years the decline in efficiency is only ~1% (based on calculations),
They retain their magnetic properties even under external field action,
A magnet with a metallic nickel surface has better aesthetics,
The surface of neodymium magnets generates a maximum magnetic field – this is a distinguishing feature,
Due to their durability and thermal resistance, neodymium magnets can operate (depending on the shape) even at high temperatures reaching 230°C or more...
Possibility of accurate machining as well as adjusting to atypical conditions,
Versatile presence in high-tech industry – they are used in magnetic memories, brushless drives, precision medical tools, also multitasking production systems.
Thanks to their power density, small magnets offer high operating force, in miniature format,

Weaknesses

Problematic aspects of neodymium magnets: tips and applications.

To avoid cracks upon strong impacts, we recommend using special steel housings. Such a solution protects the magnet and simultaneously increases its durability.
NdFeB magnets lose force when exposed to high temperatures. After reaching 80°C, many of them experience permanent weakening of strength (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 extremely resistant to heat
Magnets exposed to a humid environment can corrode. Therefore while using outdoors, we suggest using water-impermeable magnets made of rubber, plastic or other material protecting against moisture
Due to limitations in creating threads and complex shapes in magnets, we recommend using casing - magnetic mount.
Health risk to health – tiny shards of magnets can be dangerous, if swallowed, which gains importance in the aspect of protecting the youngest. It is also worth noting that tiny parts of these products are able to disrupt the diagnostic process medical after entering the body.
Higher cost of purchase is a significant factor to consider compared to ceramic magnets, especially in budget applications

Lifting parameters

Maximum lifting capacity of the magnet – what affects it?

The load parameter shown concerns the maximum value, measured under ideal test conditions, namely:

on a base made of mild steel, effectively closing the magnetic flux
possessing a massiveness of minimum 10 mm to ensure full flux closure
with an ground contact surface
under conditions of ideal adhesion (surface-to-surface)
for force applied at a right angle (in the magnet axis)
in stable room temperature

Practical lifting capacity: influencing factors

Please note that the magnet holding may be lower subject to elements below, in order of importance:

Space between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by veneer or unevenness) significantly weakens the pulling force, often by half at just 0.5 mm.
Direction of force – maximum parameter is reached only during pulling at a 90° angle. The shear force of the magnet along the surface is usually several times lower (approx. 1/5 of the lifting capacity).
Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of converting into lifting capacity.
Metal type – different alloys attracts identically. Alloy additives worsen the interaction with the magnet.
Surface finish – full contact is possible only on polished steel. Rough texture reduce the real contact area, reducing force.
Heat – NdFeB sinters have a sensitivity to temperature. When it is hot they lose power, and in frost gain strength (up to a certain limit).

Lifting capacity testing was conducted on a smooth plate of suitable thickness, under a perpendicular pulling force, however under shearing force the holding force is lower. Moreover, even a minimal clearance between the magnet’s surface and the plate lowers the load capacity.

Warnings

Operating temperature

Regular neodymium magnets (N-type) lose power when the temperature exceeds 80°C. This process is irreversible.

Allergy Warning

Warning for allergy sufferers: The nickel-copper-nickel coating contains nickel. If redness happens, immediately stop working with magnets and use protective gear.

This is not a toy

Adult use only. Tiny parts pose a choking risk, leading to serious injuries. Keep out of reach of children and animals.

Pacemakers

For implant holders: Powerful magnets affect medical devices. Keep minimum 30 cm distance or request help to work with the magnets.

Threat to navigation

Note: rare earth magnets produce a field that disrupts precision electronics. Keep a separation from your phone, tablet, and navigation systems.

Shattering risk

NdFeB magnets are ceramic materials, which means they are prone to chipping. Impact of two magnets leads to them shattering into shards.

Pinching danger

Protect your hands. Two large magnets will snap together immediately with a force of several hundred kilograms, destroying everything in their path. Exercise extreme caution!

Powerful field

Exercise caution. Neodymium magnets attract from a distance and connect with huge force, often quicker than you can react.

Threat to electronics

Powerful magnetic fields can corrupt files on payment cards, hard drives, and storage devices. Keep a distance of at least 10 cm.

Fire warning

Mechanical processing of NdFeB material carries a risk of fire hazard. Magnetic powder oxidizes rapidly with oxygen and is difficult to extinguish.

Safety First! More info about hazards in the article: Safety of working with magnets.

MP 15x7/3.5x3 / N38 - ring magnet

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MP 15x7/3.5x3 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Physical analysis of the assembly - technical parameters

1. Wall mount (shear)

2. Steel thickness impact

3. Power loss vs temp

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

Elemental analysis

Environmental data

Magnet pull force

Magnetic Induction

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Pros and cons of neodymium magnets.

Pros

Weaknesses

Lifting parameters

Maximum lifting capacity of the magnet – what affects it?

Practical lifting capacity: influencing factors

Operating temperature

Allergy Warning

This is not a toy

Pacemakers

Threat to navigation

Shattering risk

Pinching danger

Powerful field

Threat to electronics

Fire warning

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C