Key Questions to Ask When Ordering Magnetic Components Factory

Frequently Asked Questions About Magnets & Magnetism

Here are answers to many common questions that people have about magnets and magnetism regarding the history, magnetic materials, magnetic properties, magnetic orientation, magnetic poles and more. For more technical info about these areas, visit our Magnetics-101-Design Guide.

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• 1.0 History
• 2.0 The Basics
• 3.0 Magnetic Strength
• 4.0 Magnetic Field
• 5.0 Magnetic Poles
• 6.0 Magnetic Flux
• 7.0 Magnetic Orientation
• 8.0 Magnetic Characteristics
• 9.0 Magnetic Properties
• 10.0 Magnet Operating Temperatures
• 11.0 Machining Magnets
• 12.0 Magnetic Assemblies
• 13.0 Handling & Storage
• 14.0 Magnetic Resources

Send us a request for quote or contact us today for more information about our custom magnets, and let us know how we can help with your specialty requirements. Large inventory of neodymium, samarium cobalt, alnico, ceramic and flexible magnets are also available for on-line purchase at MagnetShop.com.

1.0 A BRIEF HISTORY

The ancient Greeks and Chinese discovered that certain rare stones, called lodestones, were naturally magnetized. These stones could attract small pieces of iron in a seemingly magical way, and were found to always point in the same direction when allowed to swing freely, suspended by a piece of string, or floating on water. Early navigators used these magnets as rudimentary compasses to help them determine their direction while at sea.

The word "magnet" comes from Magnesia, a district in Thessaly, Greece where it is believed that the first lodestone was mined.

Over the years, magnets have evolved into the high-strength materials we have today. It was discovered that by creating alloys of various materials, one could create similar effects to those found in natural lodestone rocks, and increase the level of magnetism.

However, it was not until the 18th century that the first man-made magnets were created. Progress in creating stronger magnetic alloys was very slow until the s when alnico magnet materials (an alloy of nickel, aluminum and cobalt) were formulated. Ferrite magnets were developed in the s and rare-earth magnets in the s. Since then, the science of magnetism has grown exponentially, and extremely powerful magnetic materials have made miniature and powerful devices possible. top

2.0 THE BASICS

What is a magnet?

Magnets can be made by placing a magnetic material, such as iron or steel, in a strong magnetic field. Permanent, temporary, and electromagnets can be produced in this manner.

The atoms forming materials that can be easily magnetized such as iron, steel, nickel, and cobalt are arranged in small units, called domains. Each domain, although microscopic in size, contains millions of billions of atoms and each domain acts like a small magnet. If a magnetic material is placed in a strong magnetic field, the individual domains, which normally point in all directions, will gradually swing around into the direction of the field. They also take over neighboring domains. When most of the domains are aligned to the field, the material becomes a magnet. top

Domains before magnetization

Domains after magnetization

What does a magnet do?

Magnets do the following things:

• Attract certain materials, such as iron, nickel, cobalt, certain steels and other alloys.
• Exert an attractive or repulsive force on other magnets (opposite poles attract, like poles repel).
• Have an effect on electrical conductors when the magnet and conductor are moving in relation to each other.
• Have an effect on the path taken by electrically charged particles traveling in free space.

Based on these effects, magnets transform energy from one form to another, without any permanent loss of their own energy. Examples of magnet functions are:

1. Mechanical to mechanical, such as attraction and repulsion.
2. Mechanical to electrical, such as generators and microphones.
3. Electrical to mechanical, such as motors, loudspeakers, charged particle deflection.
4. Mechanical to heat, such as eddy current and hysteresis torque devices.
5. Special effects, such as magneto-resistance, Hall effect devices, and magnetic resonance. top

How are magnets made?

Modern magnet materials are made through casting, pressing and sintering, compression bonding, injection molding, extruding, or calendaring processes. Once manufactured, magnets often need to be further processed by grinding or other machining processes, and then assembled into a next level assembly. Visit our manufacturing and assembly page to learn more about our custom machining and assembly capabilities. top

Are there different types of magnets available?

There are three types of magnets: permanent magnets, temporary magnets, and electromagnets.

• Permanent magnets emit a magnetic field without the need for any external source of magnetism or electrical power.
• Temporary magnets behave as magnets while attached to or close to something that emits a magnetic field, but lose this characteristic when the source of the magnetic field is removed.
• Electro-magnets require electricity in order to behave as a magnet. top

There are many different types of permanent magnet materials, each with their own unique characteristics. Each material has a family of grades that have properties slightly different from each other, though based on the same composition. top

What are permanent magnets made of?

Modern permanent magnets are made of special alloys that have been found through research to create increasingly better magnets. The most common families of permanent magnet materials today are made out of aluminum-nickel-cobalt (alnicos), strontium-iron (ferrites, also known as ceramics), neodymium-iron-boron (a.k.a. neodymium magnets, or "super magnets"), and samarium-cobalt-magnet-material. (The samarium-cobalt and neodymium-iron-boron families are collectively known as the rare-earths). top

What are Rare Earth Magnets?

Rare Earth magnets are magnets that are made out of the rare-earth group of elements. The most common rare-earth magnets are the neodymium-iron-boron (neo magnets) and samarium cobalt (SmCo magnets). top

What is a temporary magnet?

Soft iron and certain iron alloys, such as permalloy (a mixture of iron and nickel) can be very easily magnetized, even in a weak field. As soon as the field is removed, however, the magnetism is lost. These materials make excellent temporary magnets, like those used in telephones and electric motors. top

What are electromagnets?

Electromagnets are used when very strong magnets are required. Electromagnets are produced by placing a metal core (usually an iron alloy) inside a coil of wire that carries an electric current. The electricity in the coil produces a magnetic field. The strength of the electromagnet depends on the strength of the electric current and the number of coils of wire. Its polarity depends on the direction of the current flow. While the current flows, the core behaves like a magnet, but as soon as the current stops, the magnetic properties are lost. Electric motors, televisions, maglev trains, telephones, computers, and many other modern devices use electromagnets. top

What are eddy currents?

These are electrical currents that are induced when a magnetic field moves in relation to an electrical conductor that has been placed within reach of the magnetic field. In turn, these eddy currents create a magnetic field that acts to stop the relative motion of the original magnetic field and electrical conductor. top

What do magnets cost?

Magnet materials can vary significantly in cost from one to the other. Here is an approximate guide as to magnet costs:

* Note: the costs shown here are relative costs based on high volumes of magnet materials that have no special machining or other characteristics.

On a cost-per-pound basis neodymium magnets may seem very costly. However, on a cost per BHmax basis, they are not so costly. Using a more powerful magnet, enables the entire device that the magnet goes into to be miniaturized. This yields cost savings that favor more powerful magnet materials. top

Are there industry standards for magnets?

Yes. Standards have been established by the Magnetic Materials Producers Association (MMPA) and the Magnet Distributors and Fabrications Association (MDFA). Both of these associations are now a part of the International Magnetics Association. Some of the publications and standards produced by these organizations are reproduced here for your convenience. top

How do I order magnets?

To efficiently order magnets, you need to have a good idea of what you want to accomplish. Here are a few items to consider:

• General nature of application: holding, moving, lifting, etc.
• Shape of magnet desired: disc, Ring, Rectangle, etc.
• Size of magnet desired: diameter, length, width, height, etc.
• Tolerances: what variation in dimensions is allowed.
• Conditions in which magnets will be used: elevated temperature, humidity, outside, inside, etc.
• Strength of magnet required: in pounds of holding force, Gauss, etc.
• Magnet should cost no more than X: this will eliminate certain materials from consideration.
• Quantities required. (top)

3.0 MAGNETIC STRENGTH

How permanent is a magnet’s strength?

If stored away from factors that adversely affect the magnet such as power lines, other magnets, high temperatures etc., a magnet will retain its magnetism essentially forever. top

What might affect a magnet’s strength?

Factors that can affect a magnet's strength include:

• Heat
• Radiation
• Strong electrical currents in close proximity to the magnet
• Other magnets in close proximity to the magnet
• Neo magnets will corrode in high humidity environments unless they have a protective coating.

Shock and vibration do not affect modern magnet materials, unless sufficient to physically damage the material. top

Will magnets lose their power over time?

Modern magnet materials do lose a very small fraction of their magnetism over time. With samarium cobalt magnets, for example, this has been shown to be less than 1% over a period of ten years. top

Which are the strongest magnets?

The most powerful magnets available today are the rare- earth types. Of the rare-earths, neodymium magnets are the strongest. However, at elevated temperatures (of approximately 150°C and above), samarium cobalt magnets can be stronger than neo magnets, depending on the magnetic circuit. top

What are superconductors?

These are the strongest magnets. They don't need a metal core at all, but are made of coils of wire made from special metal alloys which become superconductors when cooled to very low temperatures. top

Can I make a magnet that I already have stronger?

Once a magnet is fully magnetized, it's "saturated" and cannot be made any stronger. In that sense, magnets are like buckets of water: once they are full, they can't get any "fuller". top

Can a magnet that has lost its magnetism be re-magnetized?

Provided that the material has not been damaged by extreme heat, most magnets can be re-magnetized back to their original strength. top

How do you measure the strength or power of a magnet?

Most commonly, Gaussmeters, magnetometers, or pull-testers are used to measure the strength of a magnet. Gaussmeters measure the strength in Gauss; Magnetometers measure in Gauss or arbitrary units (making it easy to compare one magnet to another); pull-testers measure pull in pounds, kilograms, or other force units. Helmholtz Coils, search coils and permeameters are also used to make sophisticated measurements of magnets.

Special Gaussmeters can cost up to several thousands of dollars. Integrated Magnetics stocks several types of Gaussmeters that range between $400 and $1,500 each. contact us if you are interested in more information regarding these or to place an order. top

If I have a NdFeB magnet with a Br of 12,300 Gauss, will I be able to measure 12,300 Gauss on its surface?

No. The Br value is measured under closed-circuit conditions. A closed-circuit magnet is not of much use. In practice, you will measure a field that is less than 12,300 Gauss close to the surface of the magnet. The actual measurement will depend on whether the magnet has any steel attached to it, how far away from the surface you make the measurement, and the size of the magnet (assuming that the measurement is being made at room temperature).

For example, a 1" diameter Grade 35 neodymium magnet that is ¼" long will measure approximately 2,500 Gauss when 1/16" away from the surface, and 2,200 Gauss when 1/8" away from the surface. top

4.0 MAGNETIC FIELD

What is the strength of the earth’s magnetic field?

The surface field strength of the earth is about 0.5 gauss, but it varies by as much as 10% depending on the strength of the crustal field. A range from 0.85 to 0.45 can be found across the globe. Geomagnetic storms can cause changes of between 1% to 5% that last from a few hours to a full day. top

How does a magnet’s strength drop off over distance?

The strength of a magnetic field drops off more or less exponentially over distance.

Here is an example of how the field (measured in Gauss) drops off with distance for a samarium cobalt Grade 18-disc magnet which is 1" in diameter and 1/2" long:

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What is the governing equation for field strength relative to distance?

For a circular magnet with a radius of R and length L, the field Bx at the centerline of the magnet at distance X from the surface can be calculated by the following formula, where Br is the residual induction of the material):

There are additional formulae that can be used to calculate the field from a rectangular magnet and magnets in other configurations. Use our on-line calculators to determine your own field levels. top

What can I use to block a magnetic field?

Only materials that are attracted to a magnet can "block" a magnetic field. Depending on how thick the blocking piece is, it will partially or completely block the magnetic field. top

5.0 MAGNETIC POLES

What are magnetic poles?

Magnetic poles are the surfaces from which the invisible lines of magnetic flux emanate and connect on return to the magnet. top

What are the standard definitions of “North” and “South” pole?

The north pole is defined as the pole of a magnet that, when free to rotate, seeks the north pole of the earth. In other words, a magnet's north pole will seek the earth's north pole. Similarly, the south pole of a magnet seeks the south pole of the earth. top

Can a particular pole be identified?

Yes, the north or south pole of a magnet can be marked if specified. top

How can you tell which is the North Pole if it’s not marked?

You can't tell by looking. You can tell by placing a compass close to the magnet. The end of the needle that normally points toward the north pole of the earth would point to the south pole of the magnet. top

6.0 MAGNETIC FLUX

How do lines of magnetic flux behave?

Lines of force are three-dimensional, surrounding a bar magnet on all sides.

Likepoles repel and unlike poles attract. When opposite poles of a magnet are brought together, the lines of force join up and the magnets pull together.

When like poles of a magnet are brought together, the lines of force push away from each other and the magnets repel each other.

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7.0 MAGNETIC ORIENTATION

What does “orientation direction” mean?

Most modern magnet materials have a "grain" in that they can be magnetized for maximum effect only through one direction. This is the "orientation direction", also known as the "easy axis", or "axis".

Un-oriented magnets (also known as "Isotropic magnets") are much weaker than oriented magnets, and can be magnetized in any direction. Oriented magnets (also known as "Anisotropic magnets") are not the same in every direction - they have a preferred direction in which they should be magnetized. top

8.0 MAGNETIC CHARACTERISTICS

Magnets are characterized by three main characteristics:

1. Residual Induction: Given the symbol Br, and measured in Gauss, this is an indication of how strong the magnet is capable of being.
2. Coercive Force: Given the symbol Hc, and measured in Oersteds, this is an indication of how difficult it is to de-magnetize the magnet.
3. Maximum Energy Product: Given the symbol BHmax, and measured in Gauss-Oersteds, this is an indication of what volume of magnet material is required to project a given level of magnetic flux. top

9.0 MAGNETIC PROPERTIES

What are the properties of commonly used magnet materials?

Here are the three important properties that characterize magnets for some of the most common magnet materials used today:

• NdFeB Magnet Materials Properties Data
• SmCo Magnet Materials Properties Data
• Alnico Magnet Materials Properties Data
• Ceramic Magnet Materials Properties Data
• Flexible Magnet Materials Properties Data

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How can I use this information?

Given a magnet size, you can estimate how much magnetic flux different materials will project at a given distance. You can also use this information to compare one material to another.

Example: How much more flux will a neodymium grade 35 magnet project as compared to a ceramic grade 5 of the same dimension at a given distance? Simply divide the Br of the neo 35 by the Br of ceramic 5 (/) to get 3.1. This means that the neo grade 35 will project 3.1 times the flux a same-size ceramic grade 5 would at a given distance.

Given the flux required at some fixed distance from the magnet, you can use this information to estimate what magnet volume will be required for different magnet materials.

Additional resources:
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Example: What volume of ceramic-5 magnets would give the same flux as a neodymium grade-35 magnet at a given distance? Simply divide the BHmax of neo-35 by the BHmax of ceramic-5 (35/3.6) to get 9.7. This means that the volume of the ceramic-5 magnets would have to be 9.7 times that of the neo-35 magnet to give you the same flux. top

10.0 MAGNET OPERATING TEMPERATURES

What are the maximum recommended operating temperatures for different magnet materials?

The maximum temperature at which a magnet will be effective depends greatly on the permeance coefficient, or "Pc" of the material. The Pc is a function of the magnetic circuit in which the magnet operates. The higher the Pc (the more "closed" the circuit), the higher temperature at which the magnet can operate without becoming severely demagnetized. Shown here are approximate maximum operating temperatures for the various classes of magnet material. At temperatures, close to those listed below, special attention may be needed in order to ensure that the magnet will not become demagnetized. top

What is maximum temperature a magnet can operate at not a set value

Magnets function at different levels of efficiency given different circuits that they operate in. The more closed the circuit the magnet is operating in, the more stable it is, and the less effect temperature will have on it. top

11.0 MACHINING MAGNETS

Can magnets be machined?

Yes, magnets can be machined. However, hard magnet materials are extremely difficult to machine, unlike flexible or rubber-type magnet materials. Magnets should be machined in the unmagnetized state as much as possible, using diamond tools and/or soft grinding wheels. In general, it is best not to try to machine hard magnet materials unless you are familiar with these specialized machining techniques. top

How much does it cost to machine magnets?

Factors that determine the cost to machine magnets include:

• Quantity: The larger the quantity, the lower the cost, since set-up charges must be amortized over the quantity, and special tooling can be created to machine larger quantities.
• Material: SmCo materials are more costly to machine since they are very brittle, flexible materials are very inexpensive to machine because of their physical characteristics.
• Shape: Complex shapes are more expensive than simple shapes; and,
• Tolerances: The closer the required tolerances, the more expensive it will be to machine the magnets. top

12.0 MAGNETIC ASSEMBLIES

What is a magnetic assembly?

Magnetic Assemblies consists of one of more magnets, along with other components, such as steel, that generally affect the functionality of the magnet.

How should magnets be assembled to my device?

If a magnet must be fastened to a device, you can use either mechanical means or adhesives to secure the magnet in place.

Adhesives are often used to secure magnets in place. If magnets are being adhered to uneven surfaces, an adhesive with plenty of "body" is required so that it will conform to the uneven surface. Hot glues have been found to work well for adhering magnets to ceramics, wood, cloth, and other materials. For magnets being adhered to metal, "super glues" can be used very effectively.

Integrated Magnetics can supply flexible magnets with adhesives already attached; simply peel off the liner and attach the magnet to your product. Contact us, or send us a request for quote for a specialty order, or visit www.magnetshop.com for large stock inventory available for on-line purchase. top

*As with all adhesive applications, it is very important to ensure that all surfaces being bonded are clean and dry before bonding.

13.0 HANDLING AND STORAGE

Tips on handling and storing magnets

• Always take special care in handling magnets! Magnets can snap together and injure personnel or damage themselves.
• Keep magnets away from magnetic media such as floppy disks, credit cards, and computer monitors.
• Store magnets in closed containers so they don't attract metal debris. 
• If several magnets are being stored, they should be stored in attracting positions.
• Because they can easily become demagnetized, alnico magnets should be stored with "keepers", iron or magnetic steel plates that connect the poles of the magnet. top

14.0 RESOURCES

What are some good magnetic reference books?

• Permanent Magnet Design Handbook, by Lester Moskowitz, a 385-page book aimed at the technical layperson.
• Permanent Magnets and their Applications, by Dr. Peter Campbell, a 203-page book aimed at the technical person.
• The Driving Force, by James Livingston, a 310- page book aimed at the non-technical reader. A very well written and interesting book on the history of magnets and some of their more exotic applications. top

Send us a Request for Quote or Contact Us today for more information about our custom magnets, and let us know how we can help with your specialty requirements. Large stock inventory of magnets are also available for on-line purchase at MagnetShop.com.

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If you are the one percent of the magnet business represented by someone replacing a magnetic latch in your cabinet kitchen cabinet, this information is not for you. If on the other hand you are building kitchen cabinets or any other industrial application that uses a magnet, read on!

Today’s magnets are strong, lightweight, and inexpensive. They are a commercial commodity. This means they are mass produced in a wide variety of sizes, types, and strength. Because they are mass produced chances are the magnet you want is being made somewhere by someone to a standard shape or size for your application. How to find that magnet is what this article is all about.

Most Magnets are made overseas and are sold and distributed through well-established channels. Working your way up that chain is important to finding good Value. For the one percent of the magnet business that is in repair or replacement then big box retailers and neighborhood hardware’s are where to start. For small quantities (less than 1,000-10,000 magnets) then an industrial supplier like Monroe Engineering will serve as a good resource. Where the manufacturer of a product using lots of magnets goes is the stock and sell distributor. This is the partner that has the relationship with the manufacturer you need. Because their business is based on very high volumes, they will offer the best combination of cost, timing, and quality.

When you reach out to a distributor the more information you provide the better served you will be. With that in mind here is “what you need to know to order a magnet”.

Standard Magnet Shapes

Each of the shapes listed comes in a wide variety of strengths and sizes. Every magnet starts life as one of these shapes. You can do secondary processes like a half dome on a bar, but that will require a tooling and process fee. Not a problem if you are buying millions, but a big cost driver at low volume. Standard magnets shapes are:

Arcs

Discs

Blocks

Cylinders/Rods

Bars

Strips

Rings

Spheres

Cubes

 Cones

 Flexible strips and sheets

Adhesive backed strips and sheets

Common Magnet Coatings

 Magnets are very hard and in addition to chipping and breaking they can corrode or “rust”. Nearly all magnets are coated or painted for appearance and longevity. These coatings are:

Nickel: If your Magnet is bright silver it is coated with Nickle steel

 Plastic: Any color you can imagine but most are black/brown

Rubber: Also, typically a dark color

Molded plastic or rubber: Magnets can be imbedded in products during plastic injection molding.

Magnet Categories, Types, and Styles and Applications

Unlike biology which gives us definitions of subgroups like genus and species, manufacturing terms and descriptions are rarely so straightforward. Because magnets are so widely used in so many applications, buying them would start with what your magnet is doing. Here are the basic categories of Magnets:

Industrial Lift Magnets: These are used for material handling in a manufacturing or production environment. There are two sub types. Both are “switched” so the magnet can be made inert. Electromagnetic lift magnets require a source of electricity. These magnets can be made very strong to lift very heavy loads. If, however, the electricity goes away so does the magnetic attraction and the load heads toward the floor. More commonly used is a pair of magnets inside a casing with a mechanical lever to reverse the Polarity of two magnets inside. These magnets are in widespread use in many Industries. They are rated by load capacity in Kilograms and pounds. They are typically made to hold three times the rating.

Industrial Sweeping and Tank Magnets: Machine Shops and metal fabricators generate metal “chips” which if they do not imbed themselves in a dirty floor are best picked up with a magnet. Industrial platers and coaters use magnets on the end of a hoist to pick up small metal parts lost in the tanks.

Pot Magnets: Pot magnets are the attaching of a magnet inside a steel cover. The steel cover then becomes the attaching point for things like hooks, studs, fasteners, and clips. These are used in households, office settings, manufacturing. Basically, they work anywhere you want to hang or attach something lightweight to metal.

Permanent Magnets: A permanent magnet means just that. It will retain its magnetic characteristics unless it is exposed to extreme temperature.

Electro Magnets: A magnet that is inert until an electrical charge is applied using a coil around a steel or Iron core. These can be made very powerful and can lift a train off the tracks or pick or launch and airplane off the deck of a carrier.

 Temporary Magnet: Becomes magnetic when in the presence of a magnetic field. Rub a paper clip on a magnet and for a short period of time it will retain the magnetic property, albeit very weakly.

 Motor Magnets: Typical in the shape of an arc or radius depending on the size of the motor. These can be tiny or gigantic, but every motor has them and there’s a lot of motors out there. Motor magnets are far and away the most common application for magnets in terms of percentage of magnets used at 35% of all magnets made.

Catches, Latches, and Clasps: Plastic encased magnetic latches and catches are used in furniture, cabinets and appliances universally. They are typically “light duty” magnets made to be strong enough to hold a small door closed but light enough to pull open by hand. They are made by the billions to standard sizes and strengths. Less than 10% of all magnets made are in these application

Electronics: This is the largest and most varied category. Every electronic device uses magnetic energy. DVD players, Televisions, X ray machines, Switches, Relays, Solenoids, Sensors, Cell Phones, Wave Guides, and on and on. To say the world operates on magnets would not be far from the truth.

 Heavy Duty Magnets: Just about any magnet that lifts a load heavier than a human can is considered heavy duty.

Light duty Magnets: Think small, any magnet a human can manipulate easily would be light duty.

Rare Earth Magnets: Todays lightweight and powerful magnets exist because some minerals can be magnetized to a greater degree than steel or Iron alone. This can further improve by combining some of them. The development of these magnets included the process by which they are made, which was patented. Most rare earth magnets have been produced only under license to these patents. Rare Earth Minerals are just that. Unlike coal there are small deposits spread around the planet with most in Asia. The rare Earth Magnets are:

Neo: Made from Neodymium, Iron and Boron. Neodymium is a mineral used both in lasers and magnets. By far the most common of all the rare earth magnets.

Ceramic Ferrite: The ceramic component resists corrosion so this magnet does not require extra coating. A tradeoff between power and cost.

Smco: Samarium Cobalt performs 2 times better at high temperatures than Neo and is more stable in performance over a range of temperature

Alnico: One of the early rare earth magnets made primarily of Aluminum, Nickle, and Cobalt. Resistant to corrosion and chemicals while stable up to 535 degrees. These are still used in Industrial settings and things like guitar pickups.

Horseshoe Magnets: The universal symbol of the magnet was simply a way to align the poles of a magnet for strength while making it easy to grasp. Simple, elegant, and effective for its time.

How Magnets Are Rated for Load

Magnets are rated several ways and unless you are an engineer the basic unit of measure is lbs. Or kilograms of force required to separate a magnet in full contact with a direct pull. Note the words “Direct Pull”. I was once challenged to pull apart two small but powerful magnets with my hands. Since magnets do not resist shear as well as direct force, I simply slid them apart sideways. Getting them back together became the problem. That is why a refrigerator magnet might be hard to peel off but can be slid around.

Sometimes magnets are not in direct contact with the item being lifted. The ability of the magnetic field to hold a given amount of weight through an air gap Is also measured. That is why your refrigerator magnet will only hold so thick a stack of documents. The magnetic field must reach through the thickness of paper.

Ultimately a magnet is measured by its “Maximum Energy Product”. This is the number of Mega Gauss Oersteds. (mgoe) The higher this value the greater the magnetic field and relative strength of the magnet will be.

Modern Neo Magnets are rated with the letter N followed by a number. The highest current rating is N-52. If the rating is followed by a letter that denotes its relative resistance to temperature. If there is no letter it is considered to meet the std for that rating.

Should you want to check the breakaway force of a magnet the Magnet Distributor and Fabricator Association has published a std. MDFA-101-95

At the end of the day “you can never have too much magnet” when it comes to matching a magnet to an application

How Magnets Work

Magnets started as a naturally occurring mineral in the form of Lodestone. The earth itself is a giant magnet. Modern magnets use different materials to achieve their great strength, but the principle of their performance is the same as the lodestone discovered about 600 BC Not all minerals are magnetic. Magnetic material like lodestone is not uniformly present in the earth’s crust. By simple definition, a magnet “Is an object that has an energy field which attracts metals like Iron, steel, and cobalt.” The word object is used because inert material can be magnetized by the creation of an electrical field around it. The “magnetic field” is a flow of energy outside the body of the object going from one pole to the other……. Negative to Positive. A metal object within that field is attracted to the object generating the field. Modern magnets are made of powder that is charged after aligning the particles to a uniform direction, literally making millions of tiny magnets work together once the powder is compressed and heated in a process called sintering. The stronger the magnet the greater the pull and reach of the magnetic field.

Choosing a Magnet Partner

Now that you know the basics of how to describe your magnet application and requirements it is time to find a partner. First, talking to the factory is out of the question in most applications. Most magnets are produced in Asia under license. They are bought in bulk and standard sizes by stock and sell distributors. The distributors are only as good as their Asian suppliers, their ability to stock a wide array of products is a function of financial strength. Because of their complexity it is quite easy to make a mistake when speccing a magnet on the internet. Do not hesitate to reach out to a search result that meets the basic criteria of your magnet. If a human being picks up the quickly and seems knowledgeable you are on your way to a good low-cost solution.

For more information, please visit Magnetic Components Factory.

See Monroe’s Magnets.