I use NIB magnets in many of my projects. NIB stands for Neodymium-Iron-Boron and are the most powerful in common use.
“Continue Reading” for lots of information such as boosting the field, measurements and links…

This is the peak field of the strongest magnet I have. Note how it is stronger at the edge at 746 mT than at the pole in the top photo of 576 mT. This is only 77% of the maximum reading.
So how strong do they get? There are different grades of NIB magnets that are up to N50. The ones I have are probably N40 – 45.

But there is a way to make a stronger field by using pyramidal magnets.

Ordinary stacking of cylinders makes some difference to the maximum field however a pyramidal stacking tends to focus the field at the top. Here with a very rough stack the reading in a very small area at the top is 831 mT.

This pyramid plus cone together did not increase the field above the truncated pyramid alone

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Separating or joining 2 big magnets is a risky business. There is a real risk of injury to fingers getting pinched. Or it may just be too hard. This wooden device allows them to be separated in a more controlled manner.

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The current permanent magnet record for 2mm gap is over 5 tesla.
Photo Date: June 16, 2013