MP 20x8/4x5 / N38 - ring magnet
ring magnet
Catalog no 030333
GTIN/EAN: 5906301812272
- 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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Need more?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 | values |
|---|---|
| Cat. no. | 030333 |
| GTIN/EAN | 5906301812272 |
| Production/Distribution | Dhit sp. z o.o. |
| 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
| properties | values | units |
|---|---|---|
| coercivity bHc ? | 860-915 | kA/m |
| coercivity bHc ? | 10.8-11.5 | kOe |
| energy density [min. - max.] ? | 287-303 | BH max KJ/m |
| energy density [min. - max.] ? | 36-38 | BH max MGOe |
| remenance Br [min. - max.] ? | 12.2-12.6 | kGs |
| remenance Br [min. - max.] ? | 1220-1260 | mT |
| actual internal force iHc | ≥ 955 | kA/m |
| actual internal force iHc | ≥ 12 | kOe |
| 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 |
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 |
|
0.67 kg / 1.47 LBS
665.0 g / 6.5 N
|
| 1 mm |
|
1.66 kg / 3.67 LBS
1662.5 g / 16.3 N
|
| 2 mm |
|
3.33 kg / 7.33 LBS
3325.0 g / 32.6 N
|
| 3 mm |
|
4.99 kg / 11.00 LBS
4987.5 g / 48.9 N
|
| 5 mm |
|
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
|
| 10 mm |
|
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
|
| 11 mm |
|
6.65 kg / 14.66 LBS
6650.0 g / 65.2 N
|
| 12 mm |
|
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% |
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.
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 |
Other offers
Advantages as well as disadvantages of Nd2Fe14B magnets.
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
- 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 magnet – what contributes to it?
- 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
- 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
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).
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!
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.
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.
Safe distance
Intense magnetic fields can corrupt files on credit cards, hard drives, and storage devices. Stay away of at least 10 cm.
Shattering risk
Beware of splinters. Magnets can explode upon violent connection, launching shards into the air. Wear goggles.
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.
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.
Dust is flammable
Combustion risk: Rare earth powder is highly flammable. Avoid machining magnets in home conditions as this may cause fire.
