HH 25x7.7 [M5] / N38 - through hole magnetic holder

Strengths and weaknesses of rare earth magnets.

In addition to their long-term stability, neodymium magnets provide the following advantages:

• They virtually do not lose strength, because even after 10 years the decline in efficiency is only ~1% (in laboratory conditions),
• Neodymium magnets are distinguished by extremely resistant to demagnetization caused by external magnetic fields,
• The use of an aesthetic finish of noble metals (nickel, gold, silver) causes the element to be more visually attractive,
• Neodymium magnets ensure maximum magnetic induction on a contact point, which ensures high operational effectiveness,
• Through (appropriate) combination of ingredients, they can achieve high thermal strength, allowing for action at temperatures reaching 230°C and above...
• Thanks to the possibility of precise shaping and customization to custom needs, magnetic components can be produced in a variety of shapes and sizes, which expands the range of possible applications,
• Wide application in high-tech industry – they are utilized in HDD drives, electric drive systems, medical devices, and industrial machines.
• Relatively small size with high pulling force – neodymium magnets offer impressive pulling force in tiny dimensions, which enables their usage in compact constructions

Disadvantages of neodymium magnets:

• At very strong impacts they can crack, therefore we recommend placing them in strong housings. A metal housing provides additional protection against damage and increases the magnet's durability.
• Neodymium magnets decrease their strength 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
• Magnets exposed to a humid environment can rust. Therefore during using outdoors, we suggest using waterproof magnets made of rubber, plastic or other material resistant to moisture
• Due to limitations in producing threads and complex shapes in magnets, we recommend using a housing - magnetic holder.
• Health risk resulting from small fragments of magnets are risky, in case of ingestion, which is particularly important in the aspect of protecting the youngest. Furthermore, tiny parts of these magnets are able to disrupt the diagnostic process medical in case of swallowing.
• High unit price – neodymium magnets cost more than other types of magnets (e.g. ferrite), which can limit application in large quantities

Maximum holding power of the magnet – what affects it?

The load parameter shown concerns the limit force, measured under laboratory conditions, specifically:

• with the use of a yoke made of special test steel, ensuring maximum field concentration
• possessing a thickness of minimum 10 mm to ensure full flux closure
• characterized by lack of roughness
• with direct contact (no coatings)
• during detachment in a direction perpendicular to the mounting surface
• in stable room temperature

Practical aspects of lifting capacity – factors

In practice, the actual holding force depends on many variables, ranked from crucial:

• Distance – the presence of foreign body (rust, dirt, gap) interrupts the magnetic circuit, which lowers capacity steeply (even by 50% at 0.5 mm).
• Pull-off angle – remember that the magnet has greatest strength perpendicularly. Under sliding down, the capacity drops drastically, often to levels of 20-30% of the nominal value.
• Base massiveness – insufficiently thick steel causes magnetic saturation, causing part of the power to be escaped to the other side.
• Material composition – not every steel attracts identically. High carbon content weaken the attraction effect.
• Base smoothness – the more even the plate, the better the adhesion and higher the lifting capacity. Unevenness acts like micro-gaps.
• Thermal conditions – NdFeB sinters have a negative temperature coefficient. At higher temperatures they are weaker, and in frost gain strength (up to a certain limit).

* Lifting capacity testing was conducted on a smooth plate of optimal thickness, under perpendicular forces, whereas under shearing force the load capacity is reduced by as much as fivefold. Moreover, even a minimal clearance {between} the magnet and the plate reduces the lifting capacity.