Array ( [PRODUCT_ID] => 333 [CATEGORY_ID] => 3 [DETECTED_SHAPE] => ring [RAW_DIMENSIONS] => Array ( [D] => 0 [H] => 5 [L] => 0 [W] => 0 [Do] => 20 [Di] => 4 ) [PC_VALUE_CALC] => 0.30848492009623 [HCB_KAm] => 860 [BR_GS] => 12400 )

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Product available Ships today (order by 14:00)

MP 20x8/4x5 / 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 030333

GTIN/EAN: 5906301812272

5.00

Diameter

20 mm [±0,1 mm]

internal diameter Ø

8/4 mm [±0,1 mm]

Height

5 mm [±0,1 mm]

Weight

11.31 g

Magnetization Direction

↑ axial

Load capacity

6.65 kg / 65.21 N

Magnetic Induction

277.16 mT / 2772 Gs

Coating

[NiCuNi] Nickel

7.75 ZŁ with VAT / pcs + price for transport

6.30 ZŁ net + 23% VAT / pcs

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Carbon Footprint – environmental impact GPSR Regulation – product safety

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Call us +48 888 99 98 98 alternatively get in touch through inquiry form through our site.
Lifting power and appearance of magnets can be estimated with our our magnetic calculator.

Orders placed before 14:00 will be shipped the same business day.

MP 20x8/4x5 / N38 - ring magnet

Specification / characteristics MP 20x8/4x5 / N38 - ring magnet

properties

properties	values
Cat. no.	030333
GTIN/EAN	5906301812272
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	20 mm [±0,1 mm]
internal diameter Ø	8/4 mm [±0,1 mm]
Height	5 mm [±0,1 mm]
Weight	11.31 g
Magnetization Direction	↑ axial
Load capacity ~ ?	6.65 kg / 65.21 N
Magnetic Induction ~ ?	277.16 mT / 2772 Gs
Coating	[NiCuNi] Nickel
Manufacturing Tolerance	±0.1 mm

Magnetic properties of material N38

Specification / characteristics MP 20x8/4x5 / 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

Physical simulation of the product - technical parameters

Presented information represent the result of a engineering analysis. Values were calculated on algorithms for the material Nd₂Fe₁₄B. Operational parameters might slightly deviate from the simulation results. Please consider these data as a preliminary roadmap when designing systems.

Table 1: Static pull force (force vs gap) - characteristics
MP 20x8/4x5 / N38

Distance (mm)	Induction (Gauss) / mT	Pull Force (kg)	Risk Status
0 mm	2424 Gs 242.4 mT	6.65 kg / 6650.0 g 65.2 N	medium risk
1 mm	2265 Gs 226.5 mT	5.81 kg / 5807.9 g 57.0 N	medium risk
2 mm	2070 Gs 207.0 mT	4.85 kg / 4851.0 g 47.6 N	medium risk
3 mm	1858 Gs 185.8 mT	3.91 kg / 3906.5 g 38.3 N	medium risk
5 mm	1437 Gs 143.7 mT	2.34 kg / 2338.7 g 22.9 N	medium risk
10 mm	691 Gs 69.1 mT	0.54 kg / 540.5 g 5.3 N	safe
15 mm	343 Gs 34.3 mT	0.13 kg / 133.3 g 1.3 N	safe
20 mm	186 Gs 18.6 mT	0.04 kg / 39.3 g 0.4 N	safe
30 mm	70 Gs 7.0 mT	0.01 kg / 5.5 g 0.1 N	safe
50 mm	18 Gs 1.8 mT	0.00 kg / 0.4 g 0.0 N	safe

Magnetic force drops significantly with every subsequent millimeter of spacing. Note that even the smallest gap (e.g., dirt, varnish, dust) noticeably diminishes the holding power. Magnetic products hold strongest at the point of direct contact; distance weakens the power. Notice how rapidly the parameters fall, when the product does not touch tightly to the metal substrate. When planning the assembly, eliminate additional spacers.

Table 2: Slippage Force (Vertical Surface)
MP 20x8/4x5 / N38

Distance (mm)	Friction coefficient	Pull Force (kg)
0 mm	Stal (~0.2)	1.33 kg / 1330.0 g 13.0 N
1 mm	Stal (~0.2)	1.16 kg / 1162.0 g 11.4 N
2 mm	Stal (~0.2)	0.97 kg / 970.0 g 9.5 N
3 mm	Stal (~0.2)	0.78 kg / 782.0 g 7.7 N
5 mm	Stal (~0.2)	0.47 kg / 468.0 g 4.6 N
10 mm	Stal (~0.2)	0.11 kg / 108.0 g 1.1 N
15 mm	Stal (~0.2)	0.03 kg / 26.0 g 0.3 N
20 mm	Stal (~0.2)	0.01 kg / 8.0 g 0.1 N
30 mm	Stal (~0.2)	0.00 kg / 2.0 g 0.0 N
50 mm	Stal (~0.2)	0.00 kg / 0.0 g 0.0 N

The table below shows the estimated shear load necessary to initiate the slippage of the magnet downwards against a upright steel wall (assuming standard friction). This value is relative to the separation distance between the magnet and the metal.

Table 3: Vertical assembly (shearing) - behavior on slippery surfaces
MP 20x8/4x5 / N38

Surface type	Friction coefficient / % Mocy	Max load (kg)
Raw steel	µ = 0.3 30% Nominalnej Siły	2.00 kg / 1995.0 g 19.6 N
Painted steel (standard)	µ = 0.2 20% Nominalnej Siły	1.33 kg / 1330.0 g 13.0 N
Oily/slippery steel	µ = 0.1 10% Nominalnej Siły	0.67 kg / 665.0 g 6.5 N
Magnet with anti-slip rubber	µ = 0.5 50% Nominalnej Siły	3.33 kg / 3325.0 g 32.6 N

When hanging a element on a upright plane (e.g., a car body), it you can count on barely about 1/5 of its nominal power. Gravity and a low friction coefficient influence the fact that holders move down easier than they pull off. Want to create a wall mount? Remember that the sliding force is significantly lower than the maximum static pull force. On a slippery surface, the element will slip down under a noticeably lighter weight. Utilizing a rubberized coating can significantly improve the result.

Table 4: Material efficiency (saturation) - power losses
MP 20x8/4x5 / N38

Steel thickness (mm)	% power	Real pull force (kg)
0.5 mm	10%	0.67 kg / 665.0 g 6.5 N
1 mm	25%	1.66 kg / 1662.5 g 16.3 N
2 mm	50%	3.33 kg / 3325.0 g 32.6 N
5 mm	100%	6.65 kg / 6650.0 g 65.2 N
10 mm	100%	6.65 kg / 6650.0 g 65.2 N

A too thin steel is incapable of absorb the entire magnetic field, which wastes potential of the holder. If you mount a strong magnet to a weak sheet, the flux will penetrate right through and the holding will be smaller. To squeeze the maximum of this neodymium's power, you require a sufficiently solid element of steel. The material oversaturation means that on delicate walls (e.g., thin profiles), the holder holds weaker. We advise picking the steel cross-section from these parameters.

Table 5: Thermal stability (material behavior) - resistance threshold
MP 20x8/4x5 / N38

Ambient temp. (°C)	Power loss	Remaining pull	Status
20 °C	0.0%	6.65 kg / 6650.0 g 65.2 N	OK
40 °C	-2.2%	6.50 kg / 6503.7 g 63.8 N	OK
60 °C	-4.4%	6.36 kg / 6357.4 g 62.4 N
80 °C	-6.6%	6.21 kg / 6211.1 g 60.9 N
100 °C	-28.8%	4.73 kg / 4734.8 g 46.4 N

Classic neodymiums change their properties parameters above the temperature limit. Avoid high temperatures – high temperature can permanently damage this magnet. With every degree above norm, the magnet's capacity briefly decreases. Avoid using this magnet in hot environments exceeding its working range. Exceeding the critical threshold will result in irreversible degradation of magnetic properties.

*Technical advisory: Thermal stability depends not only on the material grade, as well as the dimension ratios. Low-profile magnets (low Pc) are more susceptible to demagnetization at lower temperatures than taller cylinders. Red status in the table points to permanent field degradation for this particular item.

Table 6: Two magnets (repulsion) - field collision
MP 20x8/4x5 / N38

Gap (mm)	Attraction (kg) (N-S)	Repulsion (kg) (N-N)
0 mm	9.28 kg / 9284 g 91.1 N 4 012 Gs	N/A
1 mm	8.73 kg / 8732 g 85.7 N 4 701 Gs	7.86 kg / 7859 g 77.1 N ~0 Gs
2 mm	8.11 kg / 8108 g 79.5 N 4 530 Gs	7.30 kg / 7297 g 71.6 N ~0 Gs
3 mm	7.45 kg / 7448 g 73.1 N 4 342 Gs	6.70 kg / 6703 g 65.8 N ~0 Gs
5 mm	6.10 kg / 6102 g 59.9 N 3 930 Gs	5.49 kg / 5492 g 53.9 N ~0 Gs
10 mm	3.27 kg / 3265 g 32.0 N 2 875 Gs	2.94 kg / 2939 g 28.8 N ~0 Gs
20 mm	0.75 kg / 755 g 7.4 N 1 382 Gs	0.68 kg / 679 g 6.7 N ~0 Gs
50 mm	0.02 kg / 19 g 0.2 N 220 Gs	0.02 kg / 17 g 0.2 N ~0 Gs

Two magnets interact from a much further distance than a magnet and sheet setup. Such a system of two magnets produces a massive flux and a larger range of operation. Want to build a powerful holder? Use a pair of magnets instead of a neodymium and a steel. Exercise caution that when connecting a pair of magnets, the impact force is extreme. The repulsion force is a bit weaker than the attraction, but still impressive.
*Field value for N-N configuration is approximately ~0 Gs at the geometric center of the gap (resulting from vector opposition).

Table 7: Protective zones (electronics) - precautionary measures
MP 20x8/4x5 / N38

Object / Device	Limit (Gauss) / mT	Safe distance
Pacemaker	5 Gs (0.5 mT)	8.0 cm
Hearing aid	10 Gs (1.0 mT)	6.5 cm
Timepiece	20 Gs (2.0 mT)	5.0 cm
Phone / Smartphone	40 Gs (4.0 mT)	4.0 cm
Remote	50 Gs (5.0 mT)	3.5 cm
Payment card	400 Gs (40.0 mT)	1.5 cm
HDD hard drive	600 Gs (60.0 mT)	1.5 cm

Powerful magnet radiation poses a serious hazard to electronics and pacemakers. These neodymiums generate a field that prevents correct functioning of sensitive medical devices. Remember: the invisible magnetic field acts through matter and housings. Exceptional care must be exercised by people with cochlear implants and drug dispensers. Influence will be felt by: automatic timepieces, car keys, speakers, and screens. Do not bring the product near payment cards, HDD media, or sensitive navigation tools.

Table 8: Collisions (kinetic energy) - collision effects
MP 20x8/4x5 / N38

Start from (mm)	Speed (km/h)	Energy (J)
10 mm	25.67 km/h (7.13 m/s)	0.29 J
30 mm	42.38 km/h (11.77 m/s)	0.78 J
50 mm	54.68 km/h (15.19 m/s)	1.30 J
100 mm	77.33 km/h (21.48 m/s)	2.61 J

Neodymium magnets are prone to chipping – a strong collision with metal risks their cracking. Control the attraction moment – a neodymium left loose becomes dangerous. Impact energy can cause material chips or painful pinches to skin. Hold the magnet firmly during installation so it doesn't hit violently against the metal. A collision at high speed ends with a crack of the neodymium. Wear eye protection when handling with powerful specimens.

Table 9: Coating parameters (durability)
MP 20x8/4x5 / 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)

The SST (salt spray test) is an industry standard for determining coating lifespan in harsh conditions. Note the thickness of the protective layer.

Table 10: Generator data (Pc)
MP 20x8/4x5 / N38

Parameter	Value	Jedn. SI / Opis
Strumień (Flux)	7 218 Mx	72.2 µWb
Współczynnik Pc	0.31	Niski (Płaski)

Total magnetic flux flowing through the pole face. Key data for coil applications and sensors. Permeance Coefficient determines the working geometry.

Table 11: Physics of underwater searching
MP 20x8/4x5 / N38

Environment	Effective steel pull	Effect
Air (land)	6.65 kg	Standard
Water (riverbed)	7.61 kg (+0.96 kg Buoyancy gain)	+14.5%

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

In water, the magnet feels stronger thanks to Archimedes' principle. However, remember the water resistance when pulling the rope quickly.

1. Sliding resistance

*Caution: On a vertical wall, the magnet holds merely approx. 20-30% of its max power.

2. Steel thickness impact

*Thin steel (e.g. computer case) drastically reduces the holding force.

3. Heat tolerance

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

Demagnetization curve and operating point (B-H)

chart generated for permeance coefficient Pc = 0.31

The chart above illustrates the magnetic characteristics of the material within the second quadrant of the hysteresis loop. The continuous line defines the physical properties of the NdFeB alloy, and the dashed line represents the permeance coefficient (Pc), indicating how the magnet's shape affects its field strength. The intersection of these two lines (the black dot) is known as the operating point. The higher this point is on the vertical axis (Induction B), the greater the magnetic efficiency of the product in your application. A low Pc value (very flat magnets) results in a lower operating point, which may lead to irreversible loss of magnetic strength when the temperature increases.

Engineering data and GPSR

Material specification

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)|Safety information|GPSR compliance}

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: 030333-2025

Magnet Unit Converter

Force (Pull)

Force in kg

lbs

Field Strength

Gauss (Gs)

Induction (T)

Type your figure in one of the inputs, and all other values change in real-time.

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The ring magnet with a hole MP 20x8/4x5 / N38 is created for mechanical fastening, 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. This product with a force of 6.65 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. When tightening the screw, you must maintain great sensitivity. We recommend tightening manually with a screwdriver, not an impact driver, because excessive force will cause the ring to crack. 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. 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 magnets in hermetic housing 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 (20 mm), so it doesn't protrude beyond the outline.

It is a magnetic ring with a diameter of 20 mm and thickness 5 mm. The pulling force of this model is an impressive 6.65 kg, which translates to 65.21 N in newtons. The mounting hole diameter is precisely 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. In the case of connecting two rings, make sure one is turned the right way. We do not offer paired sets with marked poles in this category, but they are easy to match manually.

Strengths and weaknesses of rare earth magnets.

Advantages

Besides their stability, neodymium magnets are valued for these benefits:

They retain attractive force for around ten years – the loss is just ~1% (in theory),
They maintain their magnetic properties even under strong external field,
A magnet with a metallic silver surface has an effective appearance,
Magnets are characterized by impressive magnetic induction on the working surface,
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...
Possibility of custom creating and adjusting to atypical needs,
Universal use in advanced technology sectors – they find application in magnetic memories, motor assemblies, diagnostic systems, and modern systems.
Relatively small size with high pulling force – neodymium magnets offer high power in small dimensions, which makes them useful in small systems

Limitations

Disadvantages of NdFeB magnets:

At very strong impacts they can break, therefore we advise placing them in steel cases. A metal housing provides additional protection against damage, as well as increases the magnet's durability.
Neodymium magnets lose their force 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 stability even at temperatures up to 230°C
Due to the susceptibility of magnets to corrosion in a humid environment, we advise using waterproof magnets made of rubber, plastic or other material resistant to moisture, in case of application outdoors
We recommend casing - magnetic mechanism, due to difficulties in producing threads inside the magnet and complex forms.
Possible danger resulting from small fragments of magnets are risky, in case of ingestion, which becomes key in the context of child health protection. Furthermore, tiny parts of these products are able to be problematic in diagnostics medical when they are in the body.
High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which increases costs of application in large quantities

Lifting parameters

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

The lifting capacity listed is a result of laboratory testing conducted under standard conditions:

using a sheet made of mild steel, acting as a magnetic yoke
whose thickness reaches at least 10 mm
characterized by even structure
without any air gap between the magnet and steel
under vertical force direction (90-degree angle)
in neutral thermal conditions

Determinants of practical lifting force of a magnet

In practice, the real power depends on several key aspects, listed from the most important:

Air gap (betwixt the magnet and the plate), because even a very small distance (e.g. 0.5 mm) can cause a reduction in force by up to 50% (this also applies to paint, rust or dirt).
Force direction – note 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.
Metal thickness – the thinner the sheet, the weaker the hold. Magnetic flux penetrates through instead of converting into lifting capacity.
Material composition – different alloys reacts the same. Alloy additives worsen the attraction effect.
Plate texture – ground elements guarantee perfect abutment, which improves force. Rough surfaces weaken the grip.
Operating temperature – neodymium magnets have a negative temperature coefficient. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).

Holding force was checked on a smooth steel plate of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the lifting capacity is smaller. Moreover, even a slight gap between the magnet and the plate reduces the holding force.

H&S for magnets

Magnetic media

Intense magnetic fields can erase data on credit cards, HDDs, and storage devices. Keep a distance of min. 10 cm.

Do not drill into magnets

Fire hazard: Neodymium dust is explosive. Avoid machining magnets without safety gear as this risks ignition.

Allergy Warning

Nickel alert: The nickel-copper-nickel coating contains nickel. If skin irritation occurs, immediately stop handling magnets and use protective gear.

Keep away from electronics

An intense magnetic field negatively affects the functioning of compasses in phones and GPS navigation. Keep magnets near a smartphone to prevent damaging the sensors.

Handling rules

Use magnets with awareness. Their huge power can surprise even experienced users. Plan your moves and do not underestimate their force.

Heat warning

Do not overheat. NdFeB magnets are susceptible to heat. If you need resistance above 80°C, inquire about special high-temperature series (H, SH, UH).

Magnet fragility

Despite metallic appearance, neodymium is delicate and cannot withstand shocks. Avoid impacts, as the magnet may crumble into sharp, dangerous pieces.

Choking Hazard

Strictly keep magnets out of reach of children. Ingestion danger is significant, and the effects of magnets connecting inside the body are life-threatening.

Crushing force

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

ICD Warning

For implant holders: Strong magnetic fields disrupt medical devices. Keep at least 30 cm distance or request help to handle the magnets.

Caution! Details about risks in the article: Safety of working with magnets.

MP 20x8/4x5 / N38 - ring magnet

Need advice?

MP 20x8/4x5 / N38 - ring magnet

Magnetic properties of material N38

Physical properties of sintered neodymium magnets Nd2Fe14B at 20°C

Physical simulation of the product - technical parameters

1. Sliding resistance

2. Steel thickness impact

3. Heat tolerance

Demagnetization curve and operating point (B-H)

Material specification

Ecology and recycling (GPSR)

Force (Pull)

Field Strength

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Strengths and weaknesses of rare earth magnets.

Advantages

Limitations

Lifting parameters

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

Determinants of practical lifting force of a magnet

Magnetic media

Do not drill into magnets

Allergy Warning

Keep away from electronics

Handling rules

Heat warning

Magnet fragility

Choking Hazard

Crushing force

ICD Warning

Physical properties of sintered neodymium magnets Nd₂Fe₁₄B at 20°C