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:
A. Mechanical to mechanical – such as attraction and repulsion.
B. Mechanical to electrical – such as generators and microphones.
C. Electrical to mechanical – such as motors, loudspeakers, charged particle deflection.
D. Mechanical to heat – such as eddy current and hysteresis torque devices.
E. Special effects – such as magneto-resistance, Hall effect devices, and magnetic resonance.
Modern permanent magnets are made of special alloys that have been found through research to create increasingly better magnets. The most common families of magnet materials today are ones made out of aluminum-nickel-cobalt (Alnico), strontium-iron (Ferrites, also known as Ferrites), neodymium-iron-boron (neo magnets, sometimes referred to as “super magnets”), and samarium-cobalt. (The samarium-cobalt and neodymium-iron-boron families are collectively known as the Rare Earths).
Modern magnet materials are made through casting, pressing and sintering, compression bonding, injection molding, extruding, or calendering processes.
If a magnet is stored away from power lines, other magnets, high temperatures, and other factors that adversely affect the magnet, it will retain its magnetism essentially forever.
Modern magnet materials do lose a very small fraction of their magnetism over time. For samarium cobalt materials, for example, this has been shown to be less that 1% over a period of ten years.
The factors can affect a magnet’s strength:
(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.
The strength of a magnetic field drops off roughly 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.
|Distance, x||Field at Distance, x|
For a circular magnet with a radius of R and Length L, the field at the centerline of the magnet a distance X from the surface can be calculated by the following formula (where Br is the Residual Induction of the material):
Provided that the material has not been damaged by extreme heat, the magnet can be re-magnetized back to its original strength.
Once a magnet is fully magnetized, it cannot be made any stronger – it is “saturated.” In that sense, magnets are like buckets of water: once they are full, they can’t get any “fuller.”
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 (so it’s easy to compare one magnet to another), and Pull-Testers can measure pull in pounds, kilograms, or other force units. Special Gaussmeters can cost several thousands of dollars. We only sell the pull-test style magnetic tester, which is our pull-test kit.
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 Neo magnet that is 1/4“long, will measure approximately 2,500 Gauss 1/16” away from the surface, and 2,200 Gauss 1/8” away from the surface.
Magnetic Poles are the surfaces from which the invisible lines of magnetic flux emanate and connect on return to the magnet.
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, the North Pole of a magnet seeks the North Pole of the earth. Similarly, the South Pole of a magnet seeks the South Pole of the earth.
Yes, the North or South Pole of a magnet can be marked if specified.
It is relatively simple to identify the poles of a magnet. First, the quickest method 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. Second, it is possible to use 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 settle pointing to the North. This result contradicts the common theory that opposites attract when discussing the rules of magnetism. However, the naming convention of the poles is a historical leftover from the time when the poles were called North-seeking or South-seeking poles. Finally, you can use a compass to identify the poles. The end of the needle that normally points North will be attracted to the South pole of the magnet.
We also stock a magnetic pole indicator device to quickly determine the magnets polarity. This magnetic pole tester provides an instant zero-delay magnetic pole indication. Just press the push button to activate and the tester will indicate the appropriate magnetic pole via LED’s at once.”
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.
There are 2 types of magnets: permanent magnets and electromagnets.
Permanent magnets emit a magnetic field without the need for any external source of power. Electromagnets require electricity in order to behave as a magnet.
There are various different types of permanent magnet materials, each with their own unique characteristics. Each different material has a family of grades that have properties slightly different from each other, though based on the same composition.
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 and samarium cobalt types.
The most powerful magnets available today are the rare earths types. Of the rare earths, neodymium-iron-boron types are the strongest. However, at elevated temperatures (of approximately 150 C and above), the samarium cobalt types can be stronger that the neodymium-iron-boron types (depending on the magnetic circuit).
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”.
Unoriented 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.
Ring magnets can be magnetized this way and they are referred to as radially magnetized.
Yes, stacking two or more magnets together will act similar to a single magnet of the combined size. However, due to the air gap between the magnets, the combined holding force is slightly reduced.
Neodymium (more precisely Neodymium-Iron-Boron) magnets are the strongest permanent magnets in the world.
Ferromagnetic materials are strongly attracted by a magnetic force. The elements iron (Fe), nickel (Ni), and cobalt (Co) are the most commonly available elements. Steel is ferromagnetic because it is an alloy of iron and other metals.
You can absolutely reach us using any of the information found here.
We offer magnets which are many things, but cheap is not one of them. That doesn’t mean our magnets are not affordable, reliable, strong, and tested!
Not necessarily. The pull test is a laboratory test under ideal lab conditions. It is the breakaway force required to separate a given magnet from a flat 1018 steel plate. See attached MDFA Pull Test Standard.
When lifting an object with a magnet, many factors can affect the ability of the magnet to lift a given weight. These factors include: surface finish of magnet & object, flatness of magnet & object, coating on either surface & acceleration of lifting motion. Consult our Technical Department for more information on lifting magnets.
Yes, but only certain magnets. The only magnets we carry which meet these criteria are our flexible magnets and the bonded neodymium magnets. The flexible magnets can be cut down to size or drilled through. The bonded neodymium magnets can be machined, but we recommend only experienced machinists perform this task. All other stock magnets are brittle making them very difficult to machine.
Of the magnets we carry, three styles are rated for high temperatures. Alnico is rated the highest with an operating temperature up to 1000⁰F. Samarium Cobalt follows Alnico with an operating temperature up to 575⁰F. Ceramic magnets have an operating temperature of up to 480⁰F.
Dictionary: [nē“ōdim’ēum] is pronounced NEE-O-DIM-EE-AM.
Regulations come into play when trying to ship magnets by air. Due to the strong magnetic field emitting from some magnets they can be considered “hazardous goods”, and there are regulations enforced by the International Air Transport Association (IATA). Packages containing magnets must have a reading of .0025 gauss or less when measured from 7 feet away, or less than .00525 gauss at 15 feet from the package. If the gauss rating exceeds .00525 it cannot be shipped by air. Magnets must also be packaged securely to avoid any shifting around during transit. There are methods of packaging that can reduce the magnetic field and can allow shipment by air. Consult our inside sales department for more details.
Neodymium magnets are mainly constructed of Neodymium, Iron and Boron. Iron can oxidize very easily when exposed to moisture and will rust over time. Therefore we have most of our neodymium magnets nickel-plated to protect from oxidation.
All of the magnets we sell are listed on this website, but we can also send out a printed catalog per request. Simply click on the “REQUEST A CATALOG” link on the left of this webpage. For the most current selection and pricing please refer to the website.
No. Buymagnets.com and Bunting Magnetics Co. is not responsible for shipments once they leave our warehouse. Please ensure the products you are purchasing are eligible for import into the country you are having them shipped; each country has its own rules and regulations. All import duty and brokerage fees are a responsibility of the buyer. We do not accept returns from orders shipping outside the continuous USA.
A Bunting® Magnetics Company. To find out more please visit our main site.