A Brief History of Magnets
The ancient Greeks were the first to use a naturally occurring iron
ore called magnetite, the first application was the mariner's compass.
Magnetite then became known as lode-stone, the word lode meaning to lead.
1600 Gilbert discovered the earth is one giant magnet.
1785 Charles Coulomb discovered the square law of attraction
and repulsion between electrical charges and magnetic poles.
1820 Hans Oersted discovered that an electrical current would
deflect magnetic needles.
1830 Michael Faraday discovered electromagnetic induction.
1865 The invention of the dynamo and the start of the era of
electricity.
1873 James Maxwell published the discoveries of Gauss, Ampere
and Faraday's theories today known as Maxwell's equations of the relationship
of electricity and magnetism.
1921 Saw the introduction of Cobalt and Chrome steels.
1935 Aluminium, Nickel and Cobalt known as Alnico was developed.
1950 Philips produced the first non-metallic magnets know as
Ferrites.
1970 Stronger Samarium Cobalt magnets, known as Rare Earth magnets
became available.
1983 The Japanese patented Neodymium Iron Boron magnets.
2000 Rapid advances within Neodymium magnets continues with
ever increasing performance and corrosion resistance being developed.
Magnet Materials
There are many different magnet materials and grades to
choose from. For help in choosing which is the best for
your application, see our Application Guide.
Magnet materials generally full into four main family
groups. These are: -
Alnico
Ferrite
Samarium Cobalt (SmCo)
Neodymium-Iron-Boron (NdFeB)
This site contains the majority of our standard sizes,
which are normally available from stock or at short notice.
It is recommended you seek
This publication shows the majority of our standard sizes, which are normally available from stock or at short notice. It is recommended you seek our advice when making your selection to ensure that you are always using the correct magnet for the job. If you do not see the size you require, please ask as other sizes can often be supplied at short notice.
Handling and Safety
Anyone handling magnets must be instructed about the following safety rules:
- Pacemakers & magnetically stored data will be affected or damaged by magnets
- Beware that modern permanent magnets may attract steel or other magnets with high mechanical forces. Big magnets act over wide distances and can cause injuries.
- Most sintered magnets are hard and brittle. If such magnets snap together they may shatter into many parts with sharp edges. Always wear safety glasses when handling such magnets.
- Strong magnetic fields may influence or distort sensitive electronical or mechanical test instruments. Very sensitive devices may even be destroyed. Always keep magnets at a safe distance from such devices.
- Never handle magnets in an environment wherein explosive gas could be present. Moving or snapping of magnets, mainly those from rare-earth metals, may cause sparking.
- When machining or grinding magnets, the dust or chips may burn. The fine dust of rare-earth magnets is pyrophoric and oxidizes rapidly, causing high temperatures. Never grind such magnets without plenty of coolant, and take proper precautions for handling the grinding dust
PLEASE NOTE!
- Permanent magnets should not be exposed to strong radiation over long periods of time. Some magnetic properties may be influenced.
- Always watch for the maximum temperature to which a magnet may be exposed. Basically, rising temperatures decrease the magnetic properties.
- Neodymium magnets are extremely susceptible to corrosion, great care should be taken to avoid Hydrogen or salt water environments. These magnets must also be stored in a dry environment in order to avoid oxidisation of the surface.
INFLUENCE ON HUMAN BEINGS
No negative effects are known when touching magnets. Only very strong magnetic fields with flux densities of 1 Tesla or more and long time exposure to such fields may cause biological changes. Many reports exist, claiming beneficial effects to low and medium flux-densities. Scientific opinions are controversial.
People allergic to ceramics or certain materials may react likewise when coming in contact with magnet material, whether magnetised or not. In special cases, please, ask for more details. |
