• Permanent magnets will always be magnetic once they have been magnetized as long as they work under Curie temperature. While electromagnets are only magnetic when energized, the magnetic will disappear when the electronic shut down.
• The magnetic poles of a permanent magnets are fixed and cannot be easily changed. The magnetic polarity of the electromagnet can be easily changed by shifting the direction of the current. The polarity of an electromagnet in relation to the direction of current can be told using the right-hand screw rule.
• The magnetic strength of a permanent magnet is constant under its max operating temperature. While the magnetic strength of an electromagnet can be changed by adjusting the amount of current and the number of turns of the coil. The higher the current through the electromagnet, the stronger the magnetism. The more turns the coil of an electromagnet, the stronger the magnetism.

The part of a magnet with the strongest force is called the magnetic pole. A magnetic field exists around a magnet, and the interaction between magnets is mediated by the magnetic field. A magnet, no matter how small, has two poles. A magnet that is free to rotate in a horizontal plane always has one pole pointing south and the other pole pointing north when it is at rest. The poles pointing south are called the south pole (S) and the pole pointing north is called the north pole (N).

If a magnet is split in half, no matter how small it is, each half will have an N and S pole. So far, there is no evidence of a magnetic monopole.

Rare-earth magnets are powerful permanent magnets made of alloys of rare-earth elements. The two most common types of rare earth magnets are neodymium magnets (also known as NdFeB magnets) and samarium cobalt magnets.

The number in the grade represents the maximum magnetic energy product. For example, the maximum magnetic energy product of N35 neodymium magnets is 35 Mega-Gauss Oersted (MGOe) and the maximum energy product of N55 is 55 Mega-Gauss Oersted.

Numbers may be followed by a suffix letter (or two letters)，like N42H and N42SH. In simple terms, these letters represent the different max operating temperatures of the magnets.

You can get more details from Grades of Neodymium Magnets.

Do not cut or drill the magnets by yourself unless you are a magnets manufacturer. It is dangerous to do that by yourself because the magnet grindings generated from cutting or drilling is flammable.

Our standard tolerance is +/- 0.004’’ (+/- 0.01 mm). We certainly also provide magnets with tighter tolerances.

There is no material that can “block” magnetism. Magnetic fields can pass through wood, plastic and even lead. However, we can achieve the “magnetic shielding” effect by using Ferrous materials wisely.

Ferrous materials (iron, steel or nickel, etc) can conduct magnetic fields and redirect them. When we place a magnet into a hermetically sealed container that is made from ferrous materials, the magnetic field generated by the magnet is concentrated inside the container while the magnetic field outside the container is much smaller, because the permeability of the ferrous material is much greater than that of air.

When we send powerful magnets by air, the airline states that no magnetism should be detected close to the package. To meet this requirement, we need to place the magnets in the center of a box with a steel plate inside each of the six faces, which forming an approximate ” sealed container” mentioned above.

We provide magnets in the following coating/plating.

Nickel-Copper-Nickel (Ni-Cu-Ni),

Ni-Cu-Ni plus Epoxy,

Ni-Cu-Ni plus Plastic/Rubber,

Ni-Cu-Ni plus PTFE,

Ni-Cu-Ni plus Parylene C,

Epoxy,

Zinc (Zn),Gold (Au),

Silver (Ag),

Parylene C,

PTFE (also known as “Teflon®” or “Xylan®”),

Phosphate Passivation.

Neodymium magnets are very susceptible to corrosion, so we strongly recommend surface treatment of neodymium magnets.

SmCo magnets have better corrosion resistance compared to neodymium magnets. Therefore surface treatment is not required on SmCo magnets.

However, plating is recommended on SmCo magnets when operating in acidic, high humidity or vacuum environments.

Magnetic strength can generally be measured by devices such as pull force gauges, gauss meters and magnetic flux meters.