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What is a countersunk magnetic disc?

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White countersunk disc magnet A countersunk magnetic disc is a magnetic disc with a countersunk hole in the centre of one of its magnetic faces, either the north or south pole.
countersunk screw in magnet A countersunk hole has a flat top on one magnetic face which tapers towards the other, in the shape of a cone. This allows the magnet to be attached to a surface with a countersunk screw. The surface is kept flat as the countersunk hole allows the screw to sit flush with the magnet.
Flush screw in a countersunk magnetic disc Flush means that the top of the screw and the magnet are perfectly level and even with the surface, rather than protruding above it like other types of screws would do, in a ring magnetic disc, for example.
4.8mm countersunk screw and a 4.8mm diameter countersunk magnetic disc hole The screws used with a countersunk magnetic disc need to be the same diameter as the countersunk hole. For example, you will need a screw that is 4.8mm (0.19″) in diameter to fit inside a 4.8mm (0.19″) diameter countersunk hole in a countersunk magnetic disc.
Drilling into a kitchen cupboard Countersunk magnetic discs, with the aide of a screw, are ideal for holding wooden kitchen cabinet doors closed.

Sizes of countersunk magnetic discs

Depth, diameter, and countersunk hole diameter of a countersunk magnetic disc Countersunk magnetic discs are always measured as their diameter x depth x countersunk hole diameter.
Countersunk magnetic disc diameter 50mm and 10mm The diameter refers to the distance between the two widest points of the countersunk magnetic disc. The diameter ranges from 10mm (0.39″) to 50mm (1.97″).
Height of a countersunk magnetic disc 30mm and 2mm The depth of a basic magnetic disc is the distance between the two magnetic faces and can range from  2mm (0.079″) to 30mm (1.18″).
Diameter pf two countersunk holes in countersunk magnetic discs, 3mm and 6.2mm The diameter of the countersunk hole ranges from 3mm (0.12″) to 6.2mm (0.24″) and measures the diameter of the narrowest section of the countersunk hole.
Magnetic pull of a countersunk magnetic disc 0.9kg and 81kg The magnetic pull ranges from 0.9kg (1.98lb) to 81kg (178.57lb).
Wonkee Donkee says "The magnetic pull is the maximum weight of ferromagnetic material the magnetic disc can hold"