Due to strong magnetic force among permanent magnets, how to merge and separate strong magnets is a big and serious problem while people working with them.

Sintered neodymium magnets, even with small sizes, have very strong magnetic force that will surprise you definitely. Permanent magnets belong to dangerous object; when you handle them:

1. You should get some magnet safety-danger tips.
2. Do some clean-ups in work place to keep iron items away.
3. Prepare some tools like work glove, safety glasses and wood block, wood block is a good spacer for big strong magnets.
4. Although demagnetizer is a way to separate magnets. But it will lose magnetic force. So it is very important to know the principle of separating magnets as below picture:

Due to long shape of cylinder magnets to let you have area to grab, with the second method in the picture, you can separate two small cylinder magnets by hand. But for small thin disc magnets or other very big strong magnets, the first method is the right way. Here are the reasons:
1. Seek leverage from other object such as desk and/or find a better way to grab the magnets
2. Separate magnets apart parallel, which requires less force
There is a magnet separator tool designed by K&J Magnetics which fully taking advantage of above principle. And they also provide the method to Build Your Own Magnet Separator Tool.

To merge two big magnets, you need a block wood with sharp corner as below picture. Put big ring magnets each side of wood block, and then slide them to the side of sharp corner slowly. They will meet and grip each other at the end of corner. This is based on approach of Martin Dux from supermagnete

If you want to find a way to separate the magnets from an old hard disk, click here.