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MP 20x8/4x5 / N38 - ring magnet

ring magnet

Catalog no 030333

GTIN/EAN: 5906301812272

5.00
Load capacity 6.65 kg / 65.21 N Magnetic Induction 277.16 mT / 2772 Gs
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
Coating
[NiCuNi] Nickel

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Engineering report for this magnet

Full PDF analysis: pull and shear force, effect of distance, temperature and plate thickness, safety distances and the demagnetization curve.

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Technical of the product - 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 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

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

Engineering analysis of the magnet - data

Presented values constitute the result of a mathematical simulation. Results were calculated on models for the material Nd2Fe14B. Operational performance may differ. Please consider these data as a supplementary guide when designing systems.

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

Distance (mm) Induction (Gauss) / mT Pull Force (kg/lbs/g/N) Risk Status
0 mm 2424 Gs
242.4 mT
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
strong
1 mm 2265 Gs
226.5 mT
5.81 kg / 12.80 LBS
5807.9 g / 57.0 N
strong
2 mm 2070 Gs
207.0 mT
4.85 kg / 10.69 LBS
4851.0 g / 47.6 N
strong
3 mm 1858 Gs
185.8 mT
3.91 kg / 8.61 LBS
3906.5 g / 38.3 N
strong
5 mm 1437 Gs
143.7 mT
2.34 kg / 5.16 LBS
2338.7 g / 22.9 N
strong
10 mm 691 Gs
69.1 mT
0.54 kg / 1.19 LBS
540.5 g / 5.3 N
weak grip
15 mm 343 Gs
34.3 mT
0.13 kg / 0.29 LBS
133.3 g / 1.3 N
weak grip
20 mm 186 Gs
18.6 mT
0.04 kg / 0.09 LBS
39.3 g / 0.4 N
weak grip
30 mm 70 Gs
7.0 mT
0.01 kg / 0.01 LBS
5.5 g / 0.1 N
weak grip
50 mm 18 Gs
1.8 mT
0.00 kg / 0.00 LBS
0.4 g / 0.0 N
weak grip

Table 2: Sliding hold (vertical surface)
MP 20x8/4x5 / N38

Distance (mm) Friction coefficient Pull Force (kg/lbs/g/N)
0 mm Stal (~0.2) 1.33 kg / 2.93 LBS
1330.0 g / 13.0 N
1 mm Stal (~0.2) 1.16 kg / 2.56 LBS
1162.0 g / 11.4 N
2 mm Stal (~0.2) 0.97 kg / 2.14 LBS
970.0 g / 9.5 N
3 mm Stal (~0.2) 0.78 kg / 1.72 LBS
782.0 g / 7.7 N
5 mm Stal (~0.2) 0.47 kg / 1.03 LBS
468.0 g / 4.6 N
10 mm Stal (~0.2) 0.11 kg / 0.24 LBS
108.0 g / 1.1 N
15 mm Stal (~0.2) 0.03 kg / 0.06 LBS
26.0 g / 0.3 N
20 mm Stal (~0.2) 0.01 kg / 0.02 LBS
8.0 g / 0.1 N
30 mm Stal (~0.2) 0.00 kg / 0.00 LBS
2.0 g / 0.0 N
50 mm Stal (~0.2) 0.00 kg / 0.00 LBS
0.0 g / 0.0 N

Table 3: Vertical assembly (shearing) - vertical pull
MP 20x8/4x5 / N38

Surface type Friction coefficient / % Mocy Max load (kg/lbs/g/N)
Raw steel
µ = 0.3 30% Nominalnej Siły
2.00 kg / 4.40 LBS
1995.0 g / 19.6 N
Painted steel (standard)
µ = 0.2 20% Nominalnej Siły
1.33 kg / 2.93 LBS
1330.0 g / 13.0 N
Oily/slippery steel
µ = 0.1 10% Nominalnej Siły
0.67 kg / 1.47 LBS
665.0 g / 6.5 N
Magnet with anti-slip rubber
µ = 0.5 50% Nominalnej Siły
3.33 kg / 7.33 LBS
3325.0 g / 32.6 N

Table 4: Material efficiency (saturation) - sheet metal selection
MP 20x8/4x5 / N38

Steel thickness (mm) % power Real pull force (kg/lbs/g/N)
0.5 mm
10%
0.67 kg / 1.47 LBS
665.0 g / 6.5 N
1 mm
25%
1.66 kg / 3.67 LBS
1662.5 g / 16.3 N
2 mm
50%
3.33 kg / 7.33 LBS
3325.0 g / 32.6 N
3 mm
75%
4.99 kg / 11.00 LBS
4987.5 g / 48.9 N
5 mm
100%
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
10 mm
100%
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
11 mm
100%
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
12 mm
100%
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N

Table 5: Thermal stability (stability) - power drop
MP 20x8/4x5 / N38

Ambient temp. (°C) Power loss Remaining pull (kg/lbs/g/N) Status
20 °C 0.0% 6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
OK
40 °C -2.2% 6.50 kg / 14.34 LBS
6503.7 g / 63.8 N
OK
60 °C -4.4% 6.36 kg / 14.02 LBS
6357.4 g / 62.4 N
80 °C -6.6% 6.21 kg / 13.69 LBS
6211.1 g / 60.9 N
100 °C -28.8% 4.73 kg / 10.44 LBS
4734.8 g / 46.4 N

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

Gap (mm) Attraction (kg/lbs) (N-S) Lateral Force (kg/lbs/g/N) Repulsion (kg/lbs) (N-N)
0 mm 9.28 kg / 20.47 LBS
4 012 Gs
1.39 kg / 3.07 LBS
1393 g / 13.7 N
N/A
1 mm 8.73 kg / 19.25 LBS
4 701 Gs
1.31 kg / 2.89 LBS
1310 g / 12.8 N
7.86 kg / 17.33 LBS
~0 Gs
2 mm 8.11 kg / 17.88 LBS
4 530 Gs
1.22 kg / 2.68 LBS
1216 g / 11.9 N
7.30 kg / 16.09 LBS
~0 Gs
3 mm 7.45 kg / 16.42 LBS
4 342 Gs
1.12 kg / 2.46 LBS
1117 g / 11.0 N
6.70 kg / 14.78 LBS
~0 Gs
5 mm 6.10 kg / 13.45 LBS
3 930 Gs
0.92 kg / 2.02 LBS
915 g / 9.0 N
5.49 kg / 12.11 LBS
~0 Gs
10 mm 3.27 kg / 7.20 LBS
2 875 Gs
0.49 kg / 1.08 LBS
490 g / 4.8 N
2.94 kg / 6.48 LBS
~0 Gs
20 mm 0.75 kg / 1.66 LBS
1 382 Gs
0.11 kg / 0.25 LBS
113 g / 1.1 N
0.68 kg / 1.50 LBS
~0 Gs
50 mm 0.02 kg / 0.04 LBS
220 Gs
0.00 kg / 0.01 LBS
3 g / 0.0 N
0.02 kg / 0.04 LBS
~0 Gs
60 mm 0.01 kg / 0.02 LBS
139 Gs
0.00 kg / 0.00 LBS
1 g / 0.0 N
0.00 kg / 0.00 LBS
~0 Gs
70 mm 0.00 kg / 0.01 LBS
93 Gs
0.00 kg / 0.00 LBS
1 g / 0.0 N
0.00 kg / 0.00 LBS
~0 Gs
80 mm 0.00 kg / 0.00 LBS
65 Gs
0.00 kg / 0.00 LBS
0 g / 0.0 N
0.00 kg / 0.00 LBS
~0 Gs
90 mm 0.00 kg / 0.00 LBS
47 Gs
0.00 kg / 0.00 LBS
0 g / 0.0 N
0.00 kg / 0.00 LBS
~0 Gs
100 mm 0.00 kg / 0.00 LBS
35 Gs
0.00 kg / 0.00 LBS
0 g / 0.0 N
0.00 kg / 0.00 LBS
~0 Gs

Table 7: Hazards (implants) - warnings
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
Mechanical watch 20 Gs (2.0 mT) 5.0 cm
Mobile device 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

Table 8: Impact energy (kinetic energy) - warning
MP 20x8/4x5 / N38

Start from (mm) Speed (km/h) Energy (J) Predicted outcome
10 mm 25.22 km/h
(7.01 m/s)
0.28 J
30 mm 26.09 km/h
(7.25 m/s)
0.30 J
50 mm 26.10 km/h
(7.25 m/s)
0.30 J
100 mm 26.11 km/h
(7.25 m/s)
0.30 J

Table 9: Anti-corrosion coating 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)

Table 10: Construction data (Flux)
MP 20x8/4x5 / N38

Parameter Value SI Unit / Description
Magnetic Flux 7 218 Mx 72.2 µWb
Pc Coefficient 0.31 Low (Flat)

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

1. Vertical hold

*Caution: On a vertical wall, the magnet retains merely approx. 20-30% of its nominal pull.

2. Steel thickness impact

*Thin metal sheet (e.g. computer case) severely limits the holding force.

3. Heat tolerance

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

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

chart generated for the permeance coefficient Pc (Permeance Coefficient) = 0.31

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 Pc (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 Pc 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 and environmental data

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: 030333-2026
Measurement Calculator

Magnet pull force


Magnetic Field

Other offers

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 is a crucial issue when working with model MP 20x8/4x5 / N38. Neodymium magnets are sintered ceramics, which means they are very brittle and inelastic. One turn too many can destroy the magnet, so do it slowly. It's a good idea to use a rubber spacer under the screw head, which will cushion the stresses. 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. If you must use it outside, paint it with anti-corrosion paint after mounting.
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. Aesthetic mounting requires selecting the appropriate head size.
The presented product is a ring magnet with dimensions Ø20 mm (outer diameter) and height 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.
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.

Advantages as well as disadvantages of Nd2Fe14B magnets.

Advantages

Besides their exceptional strength, neodymium magnets offer the following advantages:
  • Their magnetic field is durable, and after around ten years it decreases only by ~1% (according to research),
  • They maintain their magnetic properties even under external field action,
  • In other words, due to the shiny finish of nickel, the element gains visual value,
  • Magnets are characterized by maximum magnetic induction on the outer side,
  • 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...
  • Thanks to flexibility in constructing and the ability to customize to specific needs,
  • Significant place in high-tech industry – they are commonly used in computer drives, motor assemblies, advanced medical instruments, and technologically advanced constructions.
  • Relatively small size with high pulling force – neodymium magnets offer strong magnetic field in tiny dimensions, which allows their use in compact constructions

Weaknesses

Disadvantages of neodymium magnets:
  • They are prone to damage upon heavy impacts. To avoid cracks, it is worth protecting magnets in special housings. Such protection not only protects the magnet but also improves its resistance to damage
  • Neodymium magnets decrease their power under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
  • They oxidize in a humid environment. For use outdoors we suggest using waterproof magnets e.g. in rubber, plastic
  • We suggest cover - magnetic mechanism, due to difficulties in producing threads inside the magnet and complicated shapes.
  • Health risk resulting from small fragments of magnets are risky, if swallowed, which becomes key in the context of child safety. It is also worth noting that small elements of these devices are able to complicate diagnosis medical after entering the body.
  • Due to neodymium price, their price is higher than average,

Lifting parameters

Optimal lifting capacity of a neodymium magnetwhat contributes to it?

Holding force of 6.65 kg is a theoretical maximum value performed under the following configuration:
  • on a block made of structural steel, effectively closing the magnetic field
  • whose transverse dimension reaches at least 10 mm
  • with a surface cleaned and smooth
  • without the slightest clearance between the magnet and steel
  • under axial force direction (90-degree angle)
  • at standard ambient temperature

Lifting capacity in real conditions – factors

Real force impacted by specific conditions, such as (from priority):
  • Space between surfaces – even a fraction of a millimeter of distance (caused e.g. by veneer or dirt) diminishes the magnet efficiency, often by half at just 0.5 mm.
  • Loading method – declared lifting capacity refers to detachment vertically. When attempting to slide, the magnet exhibits much less (often approx. 20-30% of nominal force).
  • Element thickness – to utilize 100% power, the steel must be adequately massive. Thin sheet limits the attraction force (the magnet "punches through" it).
  • Metal type – different alloys reacts the same. Alloy additives worsen the attraction effect.
  • Surface condition – ground elements guarantee perfect abutment, which increases force. Rough surfaces reduce efficiency.
  • Temperature – temperature increase results in weakening of induction. It is worth remembering the maximum operating temperature for a given model.

Holding force was checked on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under attempts to slide the magnet the load capacity is reduced by as much as fivefold. In addition, even a minimal clearance between the magnet and the plate lowers the holding force.

Precautions when working with neodymium magnets
Dust is flammable

Combustion risk: Rare earth powder is highly flammable. Avoid machining magnets in home conditions as this may cause fire.

Safe distance

Intense magnetic fields can corrupt files on credit cards, hard drives, and storage devices. Stay away of at least 10 cm.

Compass and GPS

A strong magnetic field negatively affects the functioning of compasses in phones and GPS navigation. Maintain magnets close to a device to avoid breaking the sensors.

Product not for children

These products are not toys. Eating a few magnets may result in them attracting across intestines, which poses a direct threat to life and requires urgent medical intervention.

Shattering risk

Beware of splinters. Magnets can explode upon violent connection, launching shards into the air. Wear goggles.

Health Danger

Life threat: Neodymium magnets can turn off pacemakers and defibrillators. Stay away if you have medical devices.

Handling guide

Handle magnets consciously. Their immense force can surprise even professionals. Stay alert and do not underestimate their power.

Pinching danger

Protect your hands. Two powerful magnets will join instantly with a force of massive weight, destroying everything in their path. Exercise extreme caution!

Maximum temperature

Avoid heat. NdFeB magnets are sensitive to temperature. If you require resistance above 80°C, look for special high-temperature series (H, SH, UH).

Warning for allergy sufferers

Warning for allergy sufferers: The Ni-Cu-Ni coating consists of nickel. If redness occurs, immediately stop handling magnets and wear gloves.

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