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Questions About Neodymium-SuperMagnets
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What do the specifications N40, N42, N45, etc. mean?
The specifications N40, N42, N45, N45H etc. is a measurement for the quality of the magnet material. You can read two things from this:
1. How much "magnet energy" per volume is contained in this magnetic material
2. Up to what temperature the magnet can be used
The numbers (e.g., 40, 42, 45) are equivalent to approximately the maximum energy product of the magnet (in MGOe).
The letters N, M, H and respectively the letters SH, EH or UH say something about the maximum working temperature, which can be 80, 100, 120, 150, 180 or 200 °C. Most of our magnets begin with an "N" and should be used at 80 °C.
When we speak colloquially about the "power" of a magnet, we usually mean either the holding strength by direct contact with a metal plate or the attractive force to a piece of iron (or another magnet) at a certain range.
For this "power", the applied magnet material is not decisive in and of itself, but equally important is the volume of the magnet, the form of the magnet, the proportions of the magnet (e.g., the ratio between the diameter and the thickness of a disc magnet) and the combination with other materials, so e.g., the magnet is mounted on a piece of metal, in a metal pot, or is "free-standing".
This is similarly true in relationship to working temperature. The specified maximum temperature can only be used without a problem when the aspect ratio of the magnet is "optimal". If a magnet is, for example, too thin in relation to its diameter (or side length), the maximum temperature is reached earlier.
If you take any two magnets of differing size and magnetisation from our collection, the difference in their strength is more due to the differences in their volume than the differences in their magnetisation. For this reason, the larger magnet is the stronger magnet, even when its magnetisation classification is somewhat smaller.
You can find the exact associations between these classifications and the physical values of a magnet in the table 'Physical magnet data'.
1. How much "magnet energy" per volume is contained in this magnetic material
2. Up to what temperature the magnet can be used
The numbers (e.g., 40, 42, 45) are equivalent to approximately the maximum energy product of the magnet (in MGOe).
The letters N, M, H and respectively the letters SH, EH or UH say something about the maximum working temperature, which can be 80, 100, 120, 150, 180 or 200 °C. Most of our magnets begin with an "N" and should be used at 80 °C.
When we speak colloquially about the "power" of a magnet, we usually mean either the holding strength by direct contact with a metal plate or the attractive force to a piece of iron (or another magnet) at a certain range.
For this "power", the applied magnet material is not decisive in and of itself, but equally important is the volume of the magnet, the form of the magnet, the proportions of the magnet (e.g., the ratio between the diameter and the thickness of a disc magnet) and the combination with other materials, so e.g., the magnet is mounted on a piece of metal, in a metal pot, or is "free-standing".
This is similarly true in relationship to working temperature. The specified maximum temperature can only be used without a problem when the aspect ratio of the magnet is "optimal". If a magnet is, for example, too thin in relation to its diameter (or side length), the maximum temperature is reached earlier.
If you take any two magnets of differing size and magnetisation from our collection, the difference in their strength is more due to the differences in their volume than the differences in their magnetisation. For this reason, the larger magnet is the stronger magnet, even when its magnetisation classification is somewhat smaller.
You can find the exact associations between these classifications and the physical values of a magnet in the table 'Physical magnet data'.
How strong are these magnets?
In the description of a few of our magnets, we indicate an approximate holding strength in grams or kilograms. Please note that this refers to a theoretically-attainable, maximum value that only applies under optimal conditions. The actual holding strength is dependent upon the following factors:
Incidentally: If you require the holding force in Newton, multiply our specifications in kg by 9,81 (a mass of 1 kg creates a downward force of 9,81 Newton).
- Distance between the magnet and the object it is attracted to:
If there is no direct contact, the holding strength reduces very quickly with increasing distance. Even a half millimetre air gap can possibly reduce the holding strength by half. Even a thin coat of paint on a metallic object can cause a reduction in holding strength of the magnet. - Material of the object of magnetic attraction:
The theoretical holding strength is valid when the object of magnetic attraction consists of soft iron. This value reduces by 5% with structural steel ST37; with ST70 by approx. 30%. - Surface area of the object of magnetic attraction:
The smoother the surface, the greater the holding strength. For rougher surfaces, you should anticipate a considerable reduction in holding strength. - Direction of the force:
The theoretical holding strength is valid if a vertical force applies, that is, if the object of magnetic attraction is pulled vertically by the magnet. - Thickness of the object of magnetic attraction:
The object should not be too thin or a magnetic saturation will be achieved and part of the magnetic field will remain useless.
Incidentally: If you require the holding force in Newton, multiply our specifications in kg by 9,81 (a mass of 1 kg creates a downward force of 9,81 Newton).
Where are SuperMagnets manufactured?
Our magnets are produced in China. About 140 Chinese manufacturers produce approximately 60% of all neodymium magnets worldwide. We evaluated at least a dozen different manufacturers and checked the price/benefit-relationship. Our current supplier delivers magnets of constant quality at very reasonable prices. And since we purchase magnets in large amounts and have automated nearly 100% of the order process, we are fairly certain that, with us, you will find the very best price/benefit-relationship.
Can I drill a hole in a magnet?
Drilling (or sawing) of neodymium magnets is absolutely not recommended. First of all, the material is brittle and fragile. Secondly, drilling causes combustible dust and, thirdly, the heat caused by the drill can possibly demagnetise the material.
Specialists can work with the magnets with specialised diamond-tipped tools and constant water cooling. However, this normally occurs prior to magnetisation of the material. You should also note that magnets which have lost part of their coating due to drilling will no longer be corrosion-resistant.
Specialists can work with the magnets with specialised diamond-tipped tools and constant water cooling. However, this normally occurs prior to magnetisation of the material. You should also note that magnets which have lost part of their coating due to drilling will no longer be corrosion-resistant.
Can I airfreight supermagnete?
Magnets are generally considered dangerous goods, which can only be air-shipped under certain circumstances.
According to IATA Packing Guideline 902, a shipment with magnets falls under one of three categories:
The aim is, therefore, to pass the stricter second test and airfreight the package without special measures.
The big problem with this packing regulation lies in the fact that this measurement can only be done with expensive special equipment, since most magnetic field measuring devices cannot measure such weak magnetic fields and practically no compass has sufficient sensibility or reading accuracy to administer this test in practice.
We are currently working on a gauging station in order to do those measurements for our customers if necessary and, if desired, provide the necessary shielding for the package (= ferromagnetic iron sheet). Until then we recommend to stay away from airfreight when in doubt.
If the shipment is not airfreight, magnets are not considered dangerous goods.
According to IATA Packing Guideline 902, a shipment with magnets falls under one of three categories:
- Air-freight forbidden (magnetic field too large)
If the package with the magnets (including magnetic shielding packaging) creates a magnetic field of more than 0,00525 gauss at a distance of 4,6 metres (in any direction), the transport of the package via air freight is generally forbidden.
Alternatively, a compass can be placed at this distance, and if the needle diverts by more than two degrees, it failed the test and the transport is forbidden. - Shipment unproblematic (magnetic field very small)
The second and more strict test requires that at a distance of 2,1 metres from the package a magnetic field of less than 0,002 gauss is created. (Alternative: a compass at this distance diverts by less than 0,5 degrees).
If the package passes this test, the content is considered "not magnetised" for transport purposes and the package can be shipped. In that case it is recommended to attach a shipping declaration that confirms that the package passed the stricter test and therefore can be viewed as non-magnetic. This can avoid possible delays due to inspections by authorities.
- Shipment as a declared dangerous good (for all other cases)
If the package falls between the two categories, meaning the first test was passed but not the stricter second one, the package has to be declared a dangerous good, which will lead to higher shipping costs and additional work. Also, there are certain airports that cannot be used in this case.
The aim is, therefore, to pass the stricter second test and airfreight the package without special measures.
The big problem with this packing regulation lies in the fact that this measurement can only be done with expensive special equipment, since most magnetic field measuring devices cannot measure such weak magnetic fields and practically no compass has sufficient sensibility or reading accuracy to administer this test in practice.
We are currently working on a gauging station in order to do those measurements for our customers if necessary and, if desired, provide the necessary shielding for the package (= ferromagnetic iron sheet). Until then we recommend to stay away from airfreight when in doubt.
If the shipment is not airfreight, magnets are not considered dangerous goods.
Can I send Supermagnete by mail?
If you airfreight the package, you need to adhere to strict rules. See airfreight.
If you send the package with regular mail, the rules of the postal service apply, which are different in every country. Some don't even have regulations regarding the shipment of magnets.
Nevertheless, we recommend considering a few rules, since improper packaging can lead to shipping problems. You could damage items in other packages (credit cards, hard discs, monitors, etc.) or cause disruptions with the sorting machines of the postal service. Your package could also get caught on a metal piece and content could be pulled out.
To avoid such damages you should package the magnets appropriately for shipping. You have three possibilities that you can apply separately or combined:
Paper clip test
In order to check if a package is not overly magnetic, its surfaces would have to be measured with a teslameter and an acceptable critical value would have to be determined. This is often not possible. An every-day-life test is the paper clip test: You put a paper clip to all sides of the package and it should not stick, but fall down. If you want to be even stricter, you can hold the surface not upright but at an angle of e.g. 45 degrees and see if the paper clip slides over the entire surface. If this test is successful, you should not have any problems during transport and the package should arrive safely without getting caught or damaging other items.
If you send the package with regular mail, the rules of the postal service apply, which are different in every country. Some don't even have regulations regarding the shipment of magnets.
Nevertheless, we recommend considering a few rules, since improper packaging can lead to shipping problems. You could damage items in other packages (credit cards, hard discs, monitors, etc.) or cause disruptions with the sorting machines of the postal service. Your package could also get caught on a metal piece and content could be pulled out.
To avoid such damages you should package the magnets appropriately for shipping. You have three possibilities that you can apply separately or combined:
- Arrangement of magnets
If you send several magnets together you can massively reduce the magnetic field through the proper arrangement of magnets within the package. Two or more magnets should be arranged in a way that half of the magnets are parallel to the other half, the poles pointing in opposite directions. For instance, if you want to send 50 disc magnets with a diameter of 10 mm and a thickness of 3 mm, these basically arrange themselves into a "bar" of 50 x 3 = 150 mm length. However, you should not ship this bar like that, but break it up in the middle, so that the north poles of 25 magnets point into one direction and the other half lays parallel to them, but with the north pole pointing in the other direction. This way, the magnets will be "short circuited" and the magnetic field of the package will be almost zero. Naturally, you can arrange four, six or more "bars" parallel to each other.
If you only have 2 magnets to send, it is possible that this arrangement is not stable, meaning that the magnets don't want to stay in this anti-parallel position. You can arrange the magnets on a piece of metal sheet - one magnet with its north pole towards the metal sheet, the other one with its south pole towards the metal sheet. This way, the magnets can be stabilised and the magnetic "short circuit" is even better with the metal sheet, meaning the magnetic field will decrease massively.
Several sphere magnets can be arranged in a circle in order to neutralise the magnetic field.
The goal of the arrangement has to be that, if possible, the same amount of north poles and south poles of the individual magnets point into one direction.
- Create distance
The magnetic field of a magnet decreases with increasing distance very quickly. Therefore, it is advisable to pack a rather big package and position the magnets in the middle of it. It doesn't matter if you fill up the space with paper, Styrofoam, bubble wrap, cardboard or wood. Except for sheet steel, other materials are no barriers for magnetic fields. Only the increased distance is responsible for the reduction of the magnetic field. Of course, you'll have to retain the magnets in the middle of the package, so they won't travel towards the sides of the package during the course of the transport.
Therefore, the shipping of bigger magnets in an envelope is not advisable, since the distance to the outer surface is too small.
- Shielding with sheet steel
If the "cheaper" methods of neutralisation or oversized packaging are not sufficient, you are left with utilising sheet steel for shielding. Sheet steel can be bent around a big magnet. It is not necessary that the sheet and the magnet touch each other, but it is important that the sheet steel induces a "short circuit", meaning that it reaches from the north pole to the south pole of the magnet. If you only place a sheet on the north pole and another one at the south pole and the sheets are not connected, this doesn't produce any shielding. The ideal shielding constitutes a box of sheet steel that totally encompasses the magnet. The stronger the magnet and the more complete the shielding should be, the thicker the sheet steel would have to be, so it does not reach a magnetic saturation and can induce a "magnetic short circuit".
Paper clip test
In order to check if a package is not overly magnetic, its surfaces would have to be measured with a teslameter and an acceptable critical value would have to be determined. This is often not possible. An every-day-life test is the paper clip test: You put a paper clip to all sides of the package and it should not stick, but fall down. If you want to be even stricter, you can hold the surface not upright but at an angle of e.g. 45 degrees and see if the paper clip slides over the entire surface. If this test is successful, you should not have any problems during transport and the package should arrive safely without getting caught or damaging other items.
What kind of adhesives can I use for magnets?
We recommend UHU plus endfest 300 for most applications. Therefore, we offer this article in our online shop. You can find additional information under article description.
Do magnets weaken over time?
Under normal conditions, neodymium magnets retain their magnetism nearly indefinitely. They differ in this case from conventional ferrite magnets that lose their magnetism over time, even without outside influences.
Influences that can lead to a loss of magnetic strength in neodymium magnets include:
Influences that can lead to a loss of magnetic strength in neodymium magnets include:
- heat: most of our magnets should be exposed to a maximum of 80° C
- other strong magnetic fields
How should I dispose of SuperMagnets?
According to the sanitation department of the city of Zurich, small amounts of neodymium magnets can be included in your regular garbage. Larger amounts should be taken to the old metal recycling centre.
Would it be harmful to my health to wear bracelets or necklaces made out of magnets?
This question has a short and a long answer.
Here is the short one:
I would not recommend wearing such a bracelet or necklace all the time, just once in a while on special occasions. Furthermore, if you would like to wear magnets as jewellery, I would suggest a chrome-plated magnet such as, for example, K-08-C.
Now the long answer:
Although there have been many studies on the effects of static magnetic fields on humans, and none of these has been able to prove a negative effect, you should nonetheless consider the following:
Every alternative therapist that works with magnets and every salesperson that sells "therapeutic magnets" will claim that science has not yet developed the necessary methods to detect the true effects of magnets on humans. Personally, I am very sceptical about this method of therapy and, at best, I can see how a placebo-effect can occur, as with most other alternative healing methods that also have no scientific background. However there are many people who swear by this method and it cannot be said with any certainty that it will not be proven correct in time. In this situation, in which one or the other standpoint cannot be ruled out, I would be cautious and avoid long-term contact with permanent magnets. Safe is safe.
Ultimately, you must use your own discretion when considering these facts - and it has to be said - many people regard me as over-cautious. In short you could say that, he who smokes and holds a mobile phone to his head all day won't be afraid of the potential dangers of a magnetic piece of jewellery - but those who would like to stay on the safe side will leave it alone.
Here is the short one:
I would not recommend wearing such a bracelet or necklace all the time, just once in a while on special occasions. Furthermore, if you would like to wear magnets as jewellery, I would suggest a chrome-plated magnet such as, for example, K-08-C.
Now the long answer:
Although there have been many studies on the effects of static magnetic fields on humans, and none of these has been able to prove a negative effect, you should nonetheless consider the following:
Every alternative therapist that works with magnets and every salesperson that sells "therapeutic magnets" will claim that science has not yet developed the necessary methods to detect the true effects of magnets on humans. Personally, I am very sceptical about this method of therapy and, at best, I can see how a placebo-effect can occur, as with most other alternative healing methods that also have no scientific background. However there are many people who swear by this method and it cannot be said with any certainty that it will not be proven correct in time. In this situation, in which one or the other standpoint cannot be ruled out, I would be cautious and avoid long-term contact with permanent magnets. Safe is safe.
Ultimately, you must use your own discretion when considering these facts - and it has to be said - many people regard me as over-cautious. In short you could say that, he who smokes and holds a mobile phone to his head all day won't be afraid of the potential dangers of a magnetic piece of jewellery - but those who would like to stay on the safe side will leave it alone.
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