There are four different varieties of magnetic disc available: basic, planning, ring and countersunk. These all come in a wide range of sizes, however their basic characteristic stays the same: the diameter is always greater than the depth.
Basic magnetic discs
A basic magnetic disc is the original type of magnetic disc from which the other varieties have evolved. For instance, a basic magnetic disc can be found in the casing of a planning magnetic disc.It is a type of magnetic disc where no additions have been made, for example there is no casing or countersunk hole.
Planning magnetic discs
A planning magnetic disc is a basic magnetic disc with an ABS (Acrylonite Butadiene Styrene) plastic casing. The planning magnetic disc is primarily used as a fridge magnet and the casing can come in a number of different shapes, for example flat or like a map-pin.For more information on the different shapes, see page What are the shapes of planning magnetic discs?
Ring magnetic discs
A ring magnetic disc is a basic magnetic disc with a hole which is the same width through the entire magnetic disc. It can be used as a magnetic core in a computer or as a magnetic clasp on a handbag.
Countersunk magnetic discs
A countersunk magnetic disc is a basic magnetic disc with a countersunk hole in one of its magnetic faces. This is useful for attaching the magnet to a non-ferromagnetic surface like a piece of wood, for holding kitchen cupboard doors closed.
A countersunk hole has a flat top on one magnetic face which is wider at one end than the other, almost in the shape of a cone. This keeps the surface flat as the countersunk hole allows the screw to sit flush with the magnet and the work surface e.g. a wooden cupboard door.
Flush means that the top of the screw and the magnet are perfectly level and even with one another and with the surface of whatever they have been inserted into, rather than protruding above like other types of screws would do, in a ring magnetic disc, for example.
