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
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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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 |
|---|---|---|
| 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 simulation of the assembly - report
The following data are the direct effect of a mathematical calculation. Results are based on models for the material Nd2Fe14B. Operational parameters may deviate from the simulation results. Please consider these data as a preliminary roadmap for designers.
Table 1: Static force (pull vs distance) - interaction chart
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 pounds
6650.0 g / 65.2 N
|
medium risk |
| 1 mm |
2265 Gs
226.5 mT
|
5.81 kg / 12.80 pounds
5807.9 g / 57.0 N
|
medium risk |
| 2 mm |
2070 Gs
207.0 mT
|
4.85 kg / 10.69 pounds
4851.0 g / 47.6 N
|
medium risk |
| 3 mm |
1858 Gs
185.8 mT
|
3.91 kg / 8.61 pounds
3906.5 g / 38.3 N
|
medium risk |
| 5 mm |
1437 Gs
143.7 mT
|
2.34 kg / 5.16 pounds
2338.7 g / 22.9 N
|
medium risk |
| 10 mm |
691 Gs
69.1 mT
|
0.54 kg / 1.19 pounds
540.5 g / 5.3 N
|
safe |
| 15 mm |
343 Gs
34.3 mT
|
0.13 kg / 0.29 pounds
133.3 g / 1.3 N
|
safe |
| 20 mm |
186 Gs
18.6 mT
|
0.04 kg / 0.09 pounds
39.3 g / 0.4 N
|
safe |
| 30 mm |
70 Gs
7.0 mT
|
0.01 kg / 0.01 pounds
5.5 g / 0.1 N
|
safe |
| 50 mm |
18 Gs
1.8 mT
|
0.00 kg / 0.00 pounds
0.4 g / 0.0 N
|
safe |
Table 2: Shear 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 pounds
1330.0 g / 13.0 N
|
| 1 mm | Stal (~0.2) |
1.16 kg / 2.56 pounds
1162.0 g / 11.4 N
|
| 2 mm | Stal (~0.2) |
0.97 kg / 2.14 pounds
970.0 g / 9.5 N
|
| 3 mm | Stal (~0.2) |
0.78 kg / 1.72 pounds
782.0 g / 7.7 N
|
| 5 mm | Stal (~0.2) |
0.47 kg / 1.03 pounds
468.0 g / 4.6 N
|
| 10 mm | Stal (~0.2) |
0.11 kg / 0.24 pounds
108.0 g / 1.1 N
|
| 15 mm | Stal (~0.2) |
0.03 kg / 0.06 pounds
26.0 g / 0.3 N
|
| 20 mm | Stal (~0.2) |
0.01 kg / 0.02 pounds
8.0 g / 0.1 N
|
| 30 mm | Stal (~0.2) |
0.00 kg / 0.00 pounds
2.0 g / 0.0 N
|
| 50 mm | Stal (~0.2) |
0.00 kg / 0.00 pounds
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 pounds
1995.0 g / 19.6 N
|
| Painted steel (standard) |
µ = 0.2
20% Nominalnej Siły
|
1.33 kg / 2.93 pounds
1330.0 g / 13.0 N
|
| Oily/slippery steel |
µ = 0.1
10% Nominalnej Siły
|
0.67 kg / 1.47 pounds
665.0 g / 6.5 N
|
| Magnet with anti-slip rubber |
µ = 0.5
50% Nominalnej Siły
|
3.33 kg / 7.33 pounds
3325.0 g / 32.6 N
|
Table 4: Steel thickness (substrate influence) - power losses
MP 20x8/4x5 / N38
| Steel thickness (mm) | % power | Real pull force (kg/lbs/g/N) |
|---|---|---|
| 0.5 mm |
|
0.67 kg / 1.47 pounds
665.0 g / 6.5 N
|
| 1 mm |
|
1.66 kg / 3.67 pounds
1662.5 g / 16.3 N
|
| 2 mm |
|
3.33 kg / 7.33 pounds
3325.0 g / 32.6 N
|
| 3 mm |
|
4.99 kg / 11.00 pounds
4987.5 g / 48.9 N
|
| 5 mm |
|
6.65 kg / 14.66 pounds
6650.0 g / 65.2 N
|
| 10 mm |
|
6.65 kg / 14.66 pounds
6650.0 g / 65.2 N
|
| 11 mm |
|
6.65 kg / 14.66 pounds
6650.0 g / 65.2 N
|
| 12 mm |
|
6.65 kg / 14.66 pounds
6650.0 g / 65.2 N
|
Table 5: Working in heat (stability) - resistance threshold
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 pounds
6650.0 g / 65.2 N
|
OK |
| 40 °C | -2.2% |
6.50 kg / 14.34 pounds
6503.7 g / 63.8 N
|
OK |
| 60 °C | -4.4% |
6.36 kg / 14.02 pounds
6357.4 g / 62.4 N
|
|
| 80 °C | -6.6% |
6.21 kg / 13.69 pounds
6211.1 g / 60.9 N
|
|
| 100 °C | -28.8% |
4.73 kg / 10.44 pounds
4734.8 g / 46.4 N
|
Table 6: Magnet-Magnet interaction (attraction) - field range
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 pounds
4 012 Gs
|
1.39 kg / 3.07 pounds
1393 g / 13.7 N
|
N/A |
| 1 mm |
8.73 kg / 19.25 pounds
4 701 Gs
|
1.31 kg / 2.89 pounds
1310 g / 12.8 N
|
7.86 kg / 17.33 pounds
~0 Gs
|
| 2 mm |
8.11 kg / 17.88 pounds
4 530 Gs
|
1.22 kg / 2.68 pounds
1216 g / 11.9 N
|
7.30 kg / 16.09 pounds
~0 Gs
|
| 3 mm |
7.45 kg / 16.42 pounds
4 342 Gs
|
1.12 kg / 2.46 pounds
1117 g / 11.0 N
|
6.70 kg / 14.78 pounds
~0 Gs
|
| 5 mm |
6.10 kg / 13.45 pounds
3 930 Gs
|
0.92 kg / 2.02 pounds
915 g / 9.0 N
|
5.49 kg / 12.11 pounds
~0 Gs
|
| 10 mm |
3.27 kg / 7.20 pounds
2 875 Gs
|
0.49 kg / 1.08 pounds
490 g / 4.8 N
|
2.94 kg / 6.48 pounds
~0 Gs
|
| 20 mm |
0.75 kg / 1.66 pounds
1 382 Gs
|
0.11 kg / 0.25 pounds
113 g / 1.1 N
|
0.68 kg / 1.50 pounds
~0 Gs
|
| 50 mm |
0.02 kg / 0.04 pounds
220 Gs
|
0.00 kg / 0.01 pounds
3 g / 0.0 N
|
0.02 kg / 0.04 pounds
~0 Gs
|
| 60 mm |
0.01 kg / 0.02 pounds
139 Gs
|
0.00 kg / 0.00 pounds
1 g / 0.0 N
|
0.00 kg / 0.00 pounds
~0 Gs
|
| 70 mm |
0.00 kg / 0.01 pounds
93 Gs
|
0.00 kg / 0.00 pounds
1 g / 0.0 N
|
0.00 kg / 0.00 pounds
~0 Gs
|
| 80 mm |
0.00 kg / 0.00 pounds
65 Gs
|
0.00 kg / 0.00 pounds
0 g / 0.0 N
|
0.00 kg / 0.00 pounds
~0 Gs
|
| 90 mm |
0.00 kg / 0.00 pounds
47 Gs
|
0.00 kg / 0.00 pounds
0 g / 0.0 N
|
0.00 kg / 0.00 pounds
~0 Gs
|
| 100 mm |
0.00 kg / 0.00 pounds
35 Gs
|
0.00 kg / 0.00 pounds
0 g / 0.0 N
|
0.00 kg / 0.00 pounds
~0 Gs
|
Table 7: Hazards (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 |
| Mechanical watch | 20 Gs (2.0 mT) | 5.0 cm |
| Phone / Smartphone | 40 Gs (4.0 mT) | 4.0 cm |
| Car key | 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: Collisions (cracking risk) - collision effects
MP 20x8/4x5 / N38
| Start from (mm) | Speed (km/h) | Energy (J) | Predicted outcome |
|---|---|---|---|
| 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 |
Table 9: Surface protection spec
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 (Pc)
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: Underwater work (magnet fishing)
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
*Note: On a vertical wall, the magnet holds only ~20% of its max power.
2. Plate thickness effect
*Thin metal sheet (e.g. 0.5mm PC case) significantly reduces the holding force.
3. Power loss vs temp
*For standard magnets, the critical limit is 80°C.
4. Demagnetization curve and operating point (B-H)
chart generated for the permeance coefficient Pc (Permeance Coefficient) = 0.31
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 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% |
Ecology and recycling (GPSR)
| recyclability (EoL) | 100% |
| recycled raw materials | ~10% (pre-cons) |
| carbon footprint | low / zredukowany |
| waste code (EWC) | 16 02 16 |
View also deals
Strengths as well as weaknesses of rare earth magnets.
Strengths
- Their magnetic field is durable, and after approximately ten years it drops only by ~1% (according to research),
- Magnets effectively defend themselves against demagnetization caused by ambient magnetic noise,
- Thanks to the elegant finish, the plating of nickel, gold, or silver-plated gives an aesthetic appearance,
- Magnetic induction on the surface of the magnet turns out to be maximum,
- 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...
- In view of the option of free molding and customization to custom projects, magnetic components can be produced in a wide range of geometric configurations, which increases their versatility,
- Versatile presence in advanced technology sectors – they are utilized in data components, electric motors, advanced medical instruments, also multitasking production systems.
- Compactness – despite small sizes they provide effective action, making them ideal for precision applications
Disadvantages
- Brittleness is one of their disadvantages. Upon intense impact they can break. We advise keeping them in a steel housing, which not only protects them against impacts but also raises their durability
- When exposed to high temperature, neodymium magnets experience a drop in strength. Often, when the temperature exceeds 80°C, their power decreases (depending on the size and shape of the magnet). For those who need magnets for extreme conditions, we offer [AH] versions withstanding up to 230°C
- They rust in a humid environment - during use outdoors we recommend using waterproof magnets e.g. in rubber, plastic
- We suggest a housing - magnetic holder, due to difficulties in creating threads inside the magnet and complex forms.
- Possible danger to health – tiny shards of magnets can be dangerous, if swallowed, which gains importance in the context of child safety. It is also worth noting that small components of these magnets can be problematic in diagnostics medical when they are in the body.
- With mass production the cost of neodymium magnets is a challenge,
Holding force characteristics
Maximum lifting capacity of the magnet – what it depends on?
- using a plate made of high-permeability steel, functioning as a magnetic yoke
- whose transverse dimension is min. 10 mm
- with a plane cleaned and smooth
- with total lack of distance (no paint)
- during detachment in a direction vertical to the mounting surface
- at room temperature
Practical lifting capacity: influencing factors
- Gap between magnet and steel – even a fraction of a millimeter of distance (caused e.g. by veneer or dirt) significantly weakens the magnet efficiency, often by half at just 0.5 mm.
- Force direction – note that the magnet holds strongest perpendicularly. Under sliding down, the holding force drops drastically, often to levels of 20-30% of the maximum value.
- Substrate thickness – for full efficiency, the steel must be adequately massive. Thin sheet limits the lifting capacity (the magnet "punches through" it).
- Material type – ideal substrate is high-permeability steel. Stainless steels may generate lower lifting capacity.
- Surface finish – full contact is possible only on polished steel. Any scratches and bumps reduce the real contact area, weakening the magnet.
- Thermal conditions – NdFeB sinters have a negative temperature coefficient. When it is hot they are weaker, and in frost they can be stronger (up to a certain limit).
Lifting capacity was assessed with the use of a smooth steel plate of optimal thickness (min. 20 mm), under perpendicular pulling force, however under parallel forces the lifting capacity is smaller. Additionally, even a small distance between the magnet’s surface and the plate decreases the holding force.
Safe handling of NdFeB magnets
Adults only
Strictly store magnets away from children. Ingestion danger is significant, and the effects of magnets connecting inside the body are tragic.
Combustion hazard
Dust generated during machining of magnets is combustible. Avoid drilling into magnets unless you are an expert.
Immense force
Before starting, check safety instructions. Sudden snapping can break the magnet or injure your hand. Be predictive.
Bone fractures
Large magnets can crush fingers in a fraction of a second. Under no circumstances put your hand between two attracting surfaces.
Electronic devices
Very strong magnetic fields can corrupt files on credit cards, HDDs, and other magnetic media. Keep a distance of at least 10 cm.
GPS and phone interference
An intense magnetic field disrupts the operation of magnetometers in smartphones and navigation systems. Maintain magnets close to a device to avoid breaking the sensors.
Magnets are brittle
Neodymium magnets are sintered ceramics, which means they are very brittle. Clashing of two magnets will cause them cracking into shards.
Warning for heart patients
Health Alert: Neodymium magnets can deactivate pacemakers and defibrillators. Do not approach if you have electronic implants.
Permanent damage
Avoid heat. NdFeB magnets are sensitive to heat. If you require resistance above 80°C, ask us about HT versions (H, SH, UH).
Sensitization to coating
Some people suffer from a contact allergy to Ni, which is the common plating for NdFeB magnets. Extended handling might lead to a rash. We strongly advise use safety gloves.
