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Round Neodymium Magnet 15x3, 4 mm Hole with Countersink
Permanent neodymium magnet, ideal for quick and precise fixings in industrial, electronic or DIY applications. It has a round shape, a diameter of 15 mm and a thickness of 3 mm, offers high attraction force for its size, includes a 4 mm hole for screw mounting and allows stable alignment on metal surfaces.
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The round permanent neodymium magnet is a disc with a central hole and a countersink on one of its faces, for fixing with a countersunk screw. It is used to hold panels, covers, housings or light parts on steel surfaces, to close the access doors of project boxes, and to actuate reed or Hall sensors mounted on doors and covers.
The disc has a diameter of 15 mm, a thickness of 3 mm and a central hole of 4 mm. Neodymium is a hard magnetic material that keeps its magnetization without power, and its field attracts ferromagnetic parts located nearby. The hole allows a screw with a diameter of 3 mm to pass through, and the countersink seats the screw head below the surface level, without protrusion.
The main features include the thin disc shape, the central 4 mm hole, the countersink on a single face, the flat opposite face for contact with the steel part or the sensor, and the shiny metallic finish. It is a passive component that requires no power and is installed exclusively mechanically.
Specifications:
Material: Neodymium
Shape: Disc with central hole and countersink
Outer diameter: 15 mm
Thickness: 3 mm
Hole diameter: 4 mm
Fixing type: Countersunk screw
Dimensions: 15 x 3 mm
Layout:
| Element | Function |
|---|---|
| Central hole of 4 mm | Passage of the fixing screw shank. |
| Countersink | Seating of the countersunk screw head, so that it remains below the surface level. |
| Face with countersink | Placed on the mounting surface. |
| Flat opposite face | Working face, with which the steel part is held or the magnetic sensor is actuated. |
Usage:
Choose the mounting surface and clean it of dust and grease.
Check that the part to be held is made of ferromagnetic steel, because austenitic stainless steel, aluminium, brass and plastic are not attracted.
Place the face with countersink on the mounting surface and the flat face towards the steel part or towards the sensor.
Use a countersunk screw whose shank passes through the 4 mm hole, for example a screw with a diameter of 3 mm, and check that it does not exceed the face of the magnet.
Tighten the screw gradually, with a low torque, because neodymium is brittle and may crack around the countersink. Stop when the magnet sits firmly and no longer rotates.
For Hall sensors, check the polarity of the working face before mounting, and if necessary rotate the magnet by 180 degrees.
Do not bring the magnet near pacemakers, cards, magnetic discs or compasses, and keep two neodymium magnets apart, because they can snap together with force and pinch the skin.
Avoid high temperatures and impacts, as they can weaken the magnetization or break the disc.
For stable results, keep the distance between the magnet and the part as small as possible, avoid thick paint and use steel that is thick enough, because thin steel holds more weakly.
- Dimensions
- 15 x 3 mm
- Material
- Neodymium
- Type
- Permanent magnet
- Mounting
- Countersunk head screw
- Thickness
- 3 mm
- Outer diameter
- 15 mm
- Mounting hole diameter
- 4 mm
- Shape
- Disc with central hole and conical countersink
Produs destinat utilizarii in proiecte electronice, automatizari, prototipare, educatie si cercetare.
Produsul trebuie utilizat numai conform specificatiilor tehnice mentionate in descriere si/sau in documentatia produsului.
Avertismente generale de siguranta:
Nu utilizati produsul la tensiuni, curenti sau temperaturi peste valorile specificate.
Montajul si conectarea trebuie realizate de persoane cu cunostinte tehnice minime in domeniul electric/electronic.
Evitati scurtcircuitele, inversarea polaritatii si conectarea gresita a alimentarii.
Nu lasati produsul alimentat nesupravegheat in timpul testelor.
Produsul nu este jucarie si nu este destinat copiilor.
Pentru modulele electronice, se recomanda utilizarea in carcase, panouri sau montaje protejate, dupa caz.
Identificare produs:
Denumirea produsului, codul/SKU-ul si caracteristicile tehnice sunt mentionate in pagina produsului si/sau pe eticheta ambalajului.
Producator / Importator / Distribuitor:
Sigmanortec S.R.L.
Calea Bucuresti nr. 9, Targu Jiu, Gorj, Romania
E-mail: [email protected]
Website: www.sigmanortec.ro
Persoana responsabila in UE:
Sigmanortec S.R.L.
Calea Bucuresti nr. 9, Targu Jiu, Gorj, Romania
E-mail: [email protected]
Documentatie si siguranta:
Pentru informatii suplimentare, fise tehnice, declaratii de conformitate sau instructiuni, ne puteti contacta la [email protected].
The 15x3 neodymium round magnet is a permanent disc with a diameter of 15 mm, a thickness of 3 mm and a central hole of 4 mm, with a countersunk bore on one of its faces. It is a passive part, with no electronics, so this tutorial shows how to mount and use the magnet itself, without any program.
In projects it is used to hold panels, covers, enclosures or tools on steel surfaces, to actuate reed or Hall sensors on doors and lids, and to close access doors of project boxes. The countersunk hole allows it to be fixed on wood, plastic or metal without adhesive.
How it works:
The magnet is made of neodymium, a hard magnetic material that keeps its magnetization without any power supply. The magnetic field closes through a ferromagnetic part placed nearby, for example a steel plate, and attracts it. The attractive force drops very quickly with distance, so an air gap of a few millimetres, a thick coat of paint or a layer of plastic reduces it noticeably.
An approximate calculation shows how much material the disc contains: V = pi / 4 x (D² - d²) x h = 3.14 / 4 x (15² - 4²) x 3, that is approximately 492 mm³, under 0.5 cm³. The values D = 15 mm, d = 4 mm and h = 3 mm are the dimensions of the disc. With an approximate density of neodymium of 7.5 g/cm³, the result is a mass of under 3.7 g, from which the small part removed by the countersunk bore is subtracted. It is a small and light magnet, sufficient for small parts and for actuating magnetic field sensors.
The actual holding force depends on the thickness and quality of the steel, the cleanliness of the surface and the distance between the magnet and the part. Thin steel becomes magnetically saturated and holds more weakly than a thick plate, so always check the hold on the part you will actually use.
Connection:
The magnet has no electrical connections and is not powered. It is fixed only mechanically, and the table below shows the elements of the part used for mounting.
| Product pin | Connects to | Role |
|---|---|---|
| Central 4 mm hole with countersunk bore | Countersunk head screw | Mechanical fixing on wood, plastic or metal |
| Face with the bore | Mounting surface, with the screw head in the bore | The face stays flush, with the screw head below its level |
| Opposite flat face | Steel part or the magnetic sensor | Active face, with which it holds or actuates |
Do not bring the magnet close to pacemakers, cards, magnetic disks or compasses. Two neodymium magnets can snap together with force, can break, or can pinch your skin between them, so keep them apart while working.
Setup:
Step 1: choose the mounting surface and clean it of dust and grease. If the magnet will hold a steel part, check that the steel is ferromagnetic, because austenitic stainless steel, aluminium, brass and plastic are not attracted.
Step 2: determine the working face. The flat face, without the bore, comes into contact with the steel part or the sensor. The face with the bore sits on the mounting surface, and the screw head enters the bore. If polarity matters, for example for a Hall sensor, use a compass to check which pole is on the working face and mark it on the mounting surface.
Step 3: choose a countersunk head screw whose shank passes through the 4 mm hole, for example a screw with a diameter of 3 mm. Test first that the conical part of the head seats in the bore and does not stand above the face of the magnet.
Step 4: drill a pilot hole in the mounting surface suited to the chosen screw, aligned with the hole of the magnet.
Step 5: tighten the screw gradually, with a small torque. Neodymium is brittle, and tightening too hard can crack the disc around the bore. Stop when the magnet sits firmly and no longer turns.
Usage example:
Application: actuating magnet on a door for a reed or Hall sensor mounted on the door frame. The magnet is fixed on the door leaf, and the sensor on the frame, opposite it.
Fix the sensor on the frame. Close the door and mark on the leaf the place opposite the sensor. Make the pilot hole at that place and mount the magnet with the flat face towards the sensor, following the steps from Setup. After mounting, the flat face must be parallel to the sensor, at a distance of a few millimetres when the door is closed.
Check the operation with the sensor connected to its circuit. When the door closes, the sensor output must change its state, and when the door opens it must return. If it does not react, bring the magnet closer to the sensor or rotate it by 180 degrees to reverse the polarity for Hall sensors. For reed sensors the polarity does not matter, but the actuation distance depends on the sensor model.
Common problems:
The magnet holds weakly. The usual cause is steel that is too thin, thick paint or dirt between the magnet and the part. Clean the surfaces, use a thicker steel part or eliminate the air gap.
The magnet is not attracted to the part. The material is not ferromagnetic, for example austenitic stainless steel, aluminium or brass. Check the part with another magnet and choose a common steel material.
The Hall sensor does not react. The polarity of the working face is reversed compared with what the sensor requires, or the distance is too large. Rotate the magnet by 180 degrees and reduce the distance.
The magnet cracked during mounting. The screw was tightened too hard, or the head did not fit the bore and pressed on its edge. Use a suitable countersunk head screw and tighten with care.
The magnet slides on the surface. The hold is good in the perpendicular direction, but much weaker in shear. Use two magnets or a rough surface if the part tends to slide.
Limitations and tips:
This is a small magnet, with a holding force limited by its size. Do not use it for loads that could fall and injure or damage something without prior testing. Avoid high temperatures, which can permanently weaken the magnetization, and avoid hitting the disc, because neodymium is brittle.
Keep it away from devices sensitive to magnetic fields. If you fix several magnets on the same surface, leave enough distance between them so that they do not attract each other and come loose from the mounting.
The magnet can be used further for access doors, removable panels, small tool holders and for actuating magnetic sensors to detect the opening of doors or covers.
