General Magnet Questions
1. How can I identify the poles of the magnets?Neodymium Magnet Specific
15. What are neodymium magnets? Are they the same as "rare earth"?Magnet Handling
28. How can I separate strong magnets?Platings/Coatings/Adhesives
30. Why are most neodymium magnets plated or coated?Custom/Special Magnets
33. Can you supply custom/special shapes of neodymium magnets?
Health, Safety, and Electronics
34. Are there health or safety concerns with neodymium magnets?1. How can I identify the poles of the magnets?
There are several simple methods that can be used to identify the (Scientific) North and South poles of neodymium magnets.
1) The easiest way is to use another magnet that is already marked. The North pole of the marked magnet will be attracted to the South pole of the unmarked magnet.
2) If you take an even number of magnets and pinch a string in the middle of the stack and dangle the magnets so they can freely rotate on the string, the North pole of the magnets will eventually settle pointing North. This actually contradicts the "opposites attract" rule of magnetism, but the naming convention of the poles is a carry over from the old days when the poles were called the "North-seeking" and "South-seeking" poles. These were shortened over time to the "North" and "South" poles that we know them as.
3) If you have a compass handy, the end of the needle that normally points North will be attracted to the South pole of the neodymium magnet.
2. Is one pole stronger than the other?
No, both poles are equally strong.
3. Which is the strongest type of magnet?
Neodymium (more precisely Neodymium-Iron-Boron) magnets are the strongest permanent magnets in the world.
4. What does "Magnetized thru thickness" mean?
We use the description "Magnetized thru thickness" to identify the locations of the poles on our block magnets. The thickness is always the last dimension listed for block magnets. If you take one of our block magnets and place it on a flat surface with the thickness dimension as the vertical dimension, the poles will be on the top and bottom of the magnet as it sits.
5. What materials do magnets attract?
Ferromagnetic materials are strongly attracted by a magnetic force. The elements iron (Fe), nickel (Ni), and cobalt (Co) are the most commonly available elements. Many types of steel are ferromagnetic because of the iron content. Steel is an alloy of iron, carbon and other elements.
6. What materials can I use to block/shield magnetic fields?
Magnetic fields cannot be blocked, only redirected. The only materials that will redirect magnetic fields are materials that are ferromagnetic (attracted to magnets), such as iron, steel (which contains iron), cobalt, and nickel. The degree of redirection is proportional to the permeability of the material. The most efficient shielding material is the 80 Nickel family, followed by the 50 Nickel family.
7. Can you supply monopole magnets?
No, we don't, nor does anyone else, because they don't exist. All magnets must have at least two poles.
8. Can you supply a disc/cylinder/ring/sphere magnet with one pole on the outside and one on the inside?
Disc, cylinder, and sphere shapes definitely cannot be manufactured this way. Rings magnetized this way are referred to as "radially magnetized", but it is not currently possible to manufacture neodymium ring magnets this way. We are working on it, however.
9. Does stacking magnets together make them stronger?
Yes, two or more magnets stacked together will behave exactly like a single magnet of the combined size.
10. How is the strength of a magnet measured?
Gaussmeters are used to measure the magnetic field density at the surface of the magnet. This is referred to as the surface field and is measured in Gauss (or Tesla). Pull Force Testers are used to test the holding force of a magnet that is in contact with a flat steel plate. Pull forces are measured in pounds (or kilograms).
11. How is the pull force of each magnet determined?
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All of the pull force values we specify have been tested in our laboratory. We test these magnets in two different configurations. Case 1 is the maximum pull force generated between a single magnet and a thick, ground, flat steel plate. Case 2 is the maximum pull force generated with a single magnet sandwiched between two thick, ground, flat steel plates. Case 3 is the maximum pull force generated on a magnet attracted to another magnet of the same type. The values are an average value for five samples of each magnet. A digital force gauge records the tensile force on the magnet. The plates are pulled apart until the magnet disconnects from one of the plates. The peak value is recorded as the "pull force". If using steel that is thinner, coated, or has an uneven or rusty surface, the effective pull force may be different than recorded in our lab. |
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12. I am using another online magnet pull force calculator. Why is the pull force value from the calculator different from Green Forest Magnetics' pull force?
Most other online calculators are based on theoretical formulas, which are notoriously inaccurate, especially for very large or very small sizes. Our fanatical engineers have worked long and hard in the laboratory developing our online calculators that are VERY accurate based on thousands of test cases.
13. Will a magnet with a 20 lb pull force lift a 20 lb object?
Because pull force values are tested under laboratory conditions, you probably won't achieve the same holding force under real world conditions. The effective pull force is reduced by uneven contact with the metal surface, pulling in a direction that is not perpendicular to the steel, attaching to metal that is thinner than ideal, surface coatings, and other factors.
14. What does a magnetic field look like?
The traditional way of visualizing magnetic fields is to place a magnet near a surface covered with iron filings. If you already have some of our magnets, this is a good experiment to conduct!
15. What are neodymium magnets? Are they the same as "rare earth"?
Neodymium magnets are a member of the rare earth magnet family. They are called "rare earth" because neodymium is a member of the "rare earth" elements on the periodic table. Neodymium magnets are the strongest of the rare earth magnets and are the strongest permanent magnets in the world.
16. What are neodymium magnets made from and how are they made?
Neodymium magnets are actually composed of neodymium, iron and boron (they are also referred to as NIB or NdFeB magnets). The powdered mixture is pressed under great pressure into molds. The material is then sintered (heated under a vacuum), cooled, and then ground or sliced into the desired shape. Coatings are then applied if required. Finally, the blank magnets are magnetized by exposing them to a very powerful magnetic field in excess of 30 KOe.
17. What does the "N rating", or grade, of the neodymium magnets mean?
The grade, or "N rating" of the magnet refers to the Maximum Energy Product of the material that the magnet is made from. It refers to the maximum strength that the material can be magnetize
d to. The grade of neodymium magnets is generally measured in units millions of Gauss Oersted (MGOe). A magnet of grade N42 has a Maximum Energy Product of 42 MGOe. Generally speaking, the higher the grade, the stronger the magnet.
18. Can I cut, drill, or machine neodymium magnets?
The Neodymium Iron Boron material is very hard and brittle, so machining is difficult at best. The hardness of the material is RC46 on the Rockwell "C" scale, which is harder than commercially available drills and tooling, so these tools will heat up and become damaged if used on NdFeB material. Diamond tooling, EDM (Electrostatic Discharge Machines), and abrasives are the preferred methods for shaping neodymium magnet material. Machining of neodymium magnets should only be done by experienced machinists familiar with the risk and safety issues involved. The heat generated during machining can demagnetize the magnet and could cause it to catch fire posing a safety risk. The dry powder produced while machining is also very flammable and great care must be taken to avoid combustion of this material.
19. Can I solder or weld to neodymium magnets?
You definitely cannot solder or weld to neodymium magnets. The heat will demagnetize the magnet and could cause it to catch fire posing a safety risk.
20. Do I have to worry about temperature with neodymium magnets?
Yes. Neodymium Iron Boron magnets are sensitive to heat. If a magnet heated above its maximum operating temperature (176°F (80°C) for standard N grades) the magnet will permanently lose a fraction of its magnetic strength. If they are heated above their Curie temperature (590°F (310°C) for standard N grades), they will lose all of their magnetic properties. Different grades of neodymium different maximum operating and Curie temperatures.
21. Do neodymium magnets require a keeper?
No, neodymium magnets do not require a keeper for storage like Alnico magnets.
22. Will my neodymium magnets lose strength over time?
Very little. Neodymium magnets are the strongest and most permanent magnets known to man. If they are not overheated or physically damaged, neodymium magnets will lose less than 1% of their strength over 10 years - not enough for you to notice unless you have very sensitive measuring equipment. They won't even lose their strength if they are held in repelling or attracting positions with other magnets over long periods of time.
23. Will neodymium magnets lose strength if they are held in repelling or attracting positions for a long time?
In most applications, the answer is simply "no". If the magnets will be exposed to higher temperatures while in repelling applications, the answer is "possibly". The exact answer is a bit too complicated for a FAQ answer, and requires specifics about the application.
24. How is neodymium pronounced?
From a dictionary: [nē"ōdim'ēum]
The only real trick to pronouncing it correctly is to treat the 'y' as an 'i'. It is pronounced as if it were spelled "neodimium".
25. Can I make a magnet that I already have any stronger?
No, once a magnet is fully magnetized (saturated), it cannot be made any stronger.
26. What is the difference between the maximum operating temperature and the Curie temperature of the magnets?
The maximum operating temperature is the maximum temperature the magnet may be continuously subjected to with no significant loss of magnetic strength. This is 176ºF (80ºC) for standard grades of neodymium magnets. The Curie Temperature is the temperature at which the magnet will become completely demagnetized. This is 590ºF (310ºC) for standard grades of neodymium magnets. Higher temperature grades have higher maximum operating temperatures and higher Curie Temperatures. At temperatures between these two points, a magnet will permanently lose a portion of its magnetic strength. The loss will be greater the closer to the Curie Temperature it is heated.
27. How strong of a magnetic field is necessary to magnetize a neodymium magnet?
As a general rule of thumb, a peak field of between 2 and 2.5 times the intrinsic coercivity is required to fully saturate a magnet. For standard neodymium magnets, the field required is minimum of 24 KOe, but 30 KOe is usually the minimum used.
28. How do I separate large magnets?
Small and medium-sized magnets can usually be separated by hand by sliding the end magnet off of the stack. Medium-large magnets can often be separated by using the edge of a table or countertop. Place the magnets a table top with one of the magnets hanging over the edge. Then, using your body weight, hold the magnet(s) on the table and push down on the magnet hanging over the edge. With a little work and practice, you should be able to slide the magnets apart. Just be careful that they don't snap back together once they become separated. For very large magnets (generally 2" and larger), we use a specially made magnet separating tool.
29. I have metal dust all over my magnets. How can I remove it?
Using adhesive tape to capture the metal dust is the best way to clean magnets.
30. Why are most neodymium magnets plated or coated?
Neodymium magnets are composed mainly of Neodymium, Iron, and Boron. If neodymium magnets are not plated, the iron in the material will oxidize very easily if exposed to moisture. Even normal humidity will rust the iron over time. To protect the iron from exposure to moisture, most neodymium magnets are plated or coated.
31. What is the difference between the different platings and coatings?
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Choosing a different coatings does not affect the magnetic strength or performance of the magnet, except for our Plastic and Rubber Coated Magnets. The preferred coating is dictated by preference or intended application. |
• Nickel is the most common choice for plating neodymium magnets. It is actually a triple plating of nickel-copper-nickel. It has a shiny silver finish and has good resistance to corrosion in many applications. It is not waterproof.
• Black nickel has a shiny appearance in a charcoal or gunmetal color. A black dye is added to the final nickel plating process of the triple plating of nickel-copper-black nickel. NOTE: It does not appear completely black like epoxy coatings. It is also still shiny, much like plain nickel plated magnets.
• Zinc has a dull gray/bluish finish, that is more susceptible to corrosion than nickel. Zinc can leave a black residue on hands and other items.
• Epoxy is basically a plastic coating that is more corrosion resistant as long as the coating is intact. It is easily scratched. From our experience, it is the least durable of the available coatings.
• Gold plating is applied over the top of standard nickel plating. Gold plated magnets have the same characteristics as nickel plated ones, but with a gold finish.
32. What is the thickness of the nickel (Ni-Cu-Ni) plating?
The nickel plating is actually triple plating of nickel-copper-nickel. The layers are Ni: 5-6µm, Cu: 7-8µm, Ni: 5-6µm, for a total thickness of 17-20µm.
33. I need a special size/shape of neodymium magnet. Can you supply custom magnets?
Yes, we can supply custom magnets.
34. Are there health or safety concerns with neo magnets?
There are no known health concerns with exposure to permanent magnetic fields. In fact, many people believe that magnets can be used to speed up the healing process. There may be issues with people with pacemakers handling or being around strong magnets. We are not medical professionals, so we cannot offer guidance on pacemaker safety. Please consult a physician for this information. There are several safety concerns when handling strong magnets.
35. What is a safe distance to keep magnets away from pacemakers?
We are not medical professionals, so we cannot offer guidance on pacemaker safety. Please consult a physician for this information.
36. Will magnets harm my electronics?
Maybe...The strong magnetic fields of these magnets can damage certain magnetic media such as floppy disks, credit cards, magnetic I.D. cards, cassette tapes, video tapes or other such devices. They can also damage televisions, VCRs, computer monitors and other CRT displays. Never place neodymium magnets near any of these appliances. As for other electronics such as cell phones, iPods, flash drives, calculators and similar devices that do not contain magnetic storage media, probably not, but it is best to err on the safe side and try to avoid close contact between neo magnets and electronics.
37. How far away from electronics should I keep my magnets?
This depends on a lot of factors, but as a general rule of thumb, we recommend keeping the distance between magnets and electronics 4" + 1" for every 10 lbs of pull force.
38. Will using magnets on my refrigerator, stove, oven, or microwave harm the appliance?
No, magnets will not harm any of these appliances.
39. Will magnets erase my hard drive or harm my computer?
Not unless you really work at it. While you probably don't want to stick magnets directly to your computer case, having them nearby will not harm your computer. Magnets can damage floppy disks and magnetic tape storage media, so you must keep magnets away from these items. They should not, however, damage any data on your hard drive unless you place a very large and powerful magnet directly on top of the drive. Every hard drive already contains a powerful neodymium magnet, so one moving around outside the case will not affect the data.
40. I am developing a product using magnets. Do I have to put a safety warning on it about pacemakers/electronics?
Again, we are not medical professionals, so we cannot comment on pacemaker issues. As for safety and electronics, it really depends on the application of your product, the size of the magnet(s), how the magnet is used, and where the magnet is located within the product. We recommend providing any warnings that you think may be an issue.
