Materials technology with regard to magnets is always improving.  Permenant magnets we have today are many times more powerful than those available only half a century ago.  This has caused many breakthroughs in various technologies to become possible.  This guide briefly explains some details about the latest/greatest formulation of permenant magnet.

• Power--NdFeB Magnets are the most powerful permanent magnet formulation now known to mankind. They are generally at least 7 times more powerful than standard AlNiCo and Ferrite (ceramic) magnets.

• Quality--The quality of magnetic materials is best stated by the Maximum Energy Product, in MegaGauss Oersted (MGOe). This is because the size and shape of a magnet and the material behind it (such as iron) have a large effect on the measured field strength at the surface, as does the location at which it is measured. Our NdFeB magnets range from 35 to 45 MGOe. Our surplus NdFeB magnets are also in this range, though we are unable to provide exact figures, since the materials are surplus. Another measure of the quality of a magnetic material is Br Max, which is defined to be the maximum field density a material can have. When folks talk of gauss rating, this is what they mean. Most  NdFeB magnets have Br rating of 11,000 - 14,000 Gauss.
  

• Field Strength--The unit for measuring the field strength of a magnet is the Gauss. The Earth's magnetic field is on the order of 1 Gauss, and NdFeB magnets are thousands of times more powerful than the Earth's field! We use a gauss meter to check the readings at the surface of our magnets, and we have this information available for most of our products. The size, shape and material behind a magnet all affect the field strength, as does the location at which it is measured. Maximum Energy Product is a better comparison of magnet quality.
  

• Coercivity--Coercivity is the strength of magnetic field required to magnetize, de-magnetize, or re-magnetize the NdFeB material, and it is also measured in Gauss. NdFeB magnets have a coersive gauss rating of around 12,000-14000. It has nothing to do with the actual field strength of the magnet, though highly coercive magnets are usually quite strong. This high Coercivity in NdFeB magnets also means that do not need any sort of 'keeper' during storage to retain their strength--they will last forever unless you heat them over their Curie Temperature (see below)! Actual field density (strength) of any magnet depends upon the grade and type of material, and the shape and size of the magnet.
  

• Temperature--The Curie Temperature of a magnet is the temperature at which it loses it's magnetism, permanently. Above 266 degrees F (130 C) these NdFeB magnets start to loose their power rapidly. They are NOT recommended for high heat applications. If temperature is an issue and you still need very strong magnets, you might try Samarium Cobalt magnets. They are extremely expensive, but very heat and corrosion resistant.

• Corrosion--NdFeB magnets are susceptible to corrosion. That "Fe" in the chemical name stands for iron, and it rusts! Most of our magnets come with nickel, zinc or gold plating to protect them from moisture. If the coating is damaged (from rough handling, or as on many surplus magnets that have been removed from equipment) the magnet could rust if exposed to water. If this is a concern, you can easily add another layer of protection to the magnets yourself using Plasti-Dip tool handle covering, epoxy or similar materials.
  

• Machinability--Sintered NdFeB magnets are brittle--very much like a ceramic. How brittle they are really depends on their shape and size. Folks often ask us if they can be machined. Although it is possible to cut, grind, and drill these magnets, it's difficult. They can not be heated over their Curie temperature, and again, they are quite brittle. The material is also flammable. In the process of grinding or machining, it is possible for sparks to ignite either the chips or the magnets. Once they ignite, they burn hot and the fumes are toxic. They are best machined with diamond tools under lots of coolant. We do not advise folks to try, it usually results in broken tools and/or magnets!
• NdFeB Magnets are a relatively new invention--they first became commercially available in 1984. NdFeB magnets are currently protected under patent.  The high power formulation has caused many breakthroughs in the size and efficiency of motors, alternators, sound equipment etc.  Since they've become available at an affordable price many new things have become possible.
  

• NdFeB Magnets are complicated to manufacture. The powdered materials are packed in molds, then sintered. The non-magnetized 'magnets' are then shaped to the correct sized and plated with nickel, zinc or gold. To magnetize them, they are placed in a machine that generates an extremely high-powered magnetic field for an instant, using a high voltage capacitor discharge and coil. The polarity of the finished magnet depends on how it was oriented in the machine, and how the particles in the sintered mixture are oriented.