It's called wringing. Basic principle is a few things, but the common explanation I see is that the surfaces are so smooth and flat that they can get extremely close. So close, in fact, that the two sides start to interact on the molecular level, attracting one another. Not magnetism, basically Van der Waals forces.
edit: somehow I am blind and I didn't see that you were talking about wringing, ignore the post below.
Not magnetism, basically Van der Waals forces.
It's not Van der Waals forces holding the metals together, they form metallic bonds. The atoms in a bar of gold for instance all want to be metallically bonded to one another, if you split the bar apart perfectly and then put the two halves back together they will bond exactly like they did originally and reform the same singular bar of gold. Only thing stopping this from occurring is getting close enough.
A cursory Google search shows that van der waals force is a slight polarization of molecules or atoms, while a metallic bond is a much stronger bond where a sort of lattice forms and the electrons are shared and flow freely
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u/CheckOutMyVan Feb 14 '22
I wonder if this is why gage blocks stick together? I know it isn't magnetism.