HH 16x5.3 [M3] / N38 - through hole magnetic holder

Advantages as well as disadvantages of neodymium magnets NdFeB.

In addition to their remarkable pulling force, neodymium magnets offer the following advantages:

• They do not lose their magnetism, even after around 10 years – the decrease of power is only ~1% (based on measurements),
• They show superior resistance to demagnetization from external field exposure,
• Thanks to the shiny finish and silver coating, they have an elegant appearance,
• The outer field strength of the magnet shows elevated magnetic properties,
• Thanks to their exceptional temperature resistance, they can operate (depending on the shape) even at temperatures up to 230°C or more,
• Thanks to the possibility in shaping and the capability to adapt to unique requirements, neodymium magnets can be created in different geometries, which expands their functional possibilities,
• Important function in modern technologies – they find application in data storage devices, electromechanical systems, medical equipment as well as technologically developed systems,
• Relatively small size with high magnetic force – neodymium magnets offer impressive pulling strength in tiny dimensions, which makes them useful in miniature devices

Disadvantages of NdFeB magnets:

• They are fragile when subjected to a strong impact. If the magnets are exposed to mechanical hits, they should be placed in a protective enclosure. The steel housing, in the form of a holder, protects the magnet from breakage and increases its overall resistance,
• They lose power at extreme temperatures. Most neodymium magnets experience permanent loss in strength when heated above 80°C (depending on the shape and height). However, we offer special variants with high temperature resistance that can operate up to 230°C or higher,
• Magnets exposed to wet conditions can rust. Therefore, for outdoor applications, we suggest waterproof types made of plastic,
• The use of a protective casing or external holder is recommended, since machining threads in neodymium magnets is not feasible,
• Possible threat from tiny pieces may arise, if ingested accidentally, which is notable in the health of young users. Furthermore, tiny components from these devices may complicate medical imaging after being swallowed,
• Due to expensive raw materials, their cost is considerably higher,

Maximum holding power of the magnet – what it depends on?

The given pulling force of the magnet means the maximum force, calculated in a perfect environment, that is:

• with mild steel, serving as a magnetic flux conductor
• of a thickness of at least 10 mm
• with a polished side
• in conditions of no clearance
• in a perpendicular direction of force
• under standard ambient temperature

Impact of factors on magnetic holding capacity in practice

The lifting capacity of a magnet depends on in practice the following factors, ordered from most important to least significant:

• Air gap between the magnet and the plate, since even a very small distance (e.g. 0.5 mm) can cause a drop in lifting force of up to 50%.
• Direction of applied force, because the maximum lifting capacity is achieved under perpendicular application. The force required to slide the magnet along the plate is usually several times lower.
• Thickness of the plate, as a plate that is too thin causes part of the magnetic flux not to be used and to remain wasted in the air.
• Material of the plate, because higher carbon content lowers holding force, while higher iron content increases it. The best choice is steel with high magnetic permeability and high saturation induction.
• Surface of the plate, because the more smooth and polished it is, the better the contact and consequently the greater the magnetic saturation.
• Operating temperature, since all permanent magnets have a negative temperature coefficient. This means that at high temperatures they are weaker, while at sub-zero temperatures they become slightly stronger.

* Holding force was measured on the plate surface of 20 mm thickness, when a perpendicular force was applied, whereas under parallel forces the load capacity is reduced by as much as fivefold. Moreover, even a slight gap {between} the magnet and the plate reduces the lifting capacity.