Magnets and sheet metal: Will a 45lb pull magnet (for example) hold with full force of 45lb to thin steel?

Question

More specifically - will a magnetic base or other powerful magnet hold with full power to sheet metal epoxied thoroughly to a flat surface as well as it would to a lager mass of thicker steel?

Does the mass of steel available for holding to matter?

Answer 1

No, the magnet won't hold a thin plate with the full force.  There must be enough metal to offer a negligible reluctance to the magnetic field, which requires a thickness comparable to the dimensions of the magnet's pole pieces and a cross section at least comparable to that of the magnet.  The metal being picked up must also fit closely to the magnet's pole pieces with a minimum of air gap.  The magnetic properties of the metal being picked up will also have some effect on the force with which the magnet holds it.