Magnets - Retaining Magnets
Berger Tools Limited stocks a wide range of magnets, in a variety of strengths, and designed for lifting, sorting and retaining purposes. A retaining magnet is a good option for fixing items in place without causing any damage, and some have rubber jackets to further protect the contact surface. Fixing methods vary, but for those magnets which will be screwed in place, ie. with a tapped hole or through bore, it is important that the screws be made of non magnetic material in order to avoid affecting the magnetic forces. Other fixing opting include gluing or shrinking in place, or the use of the threaded bush or stud incorporated in the magnet.
A pot magnet consists of a steel shell containing a powerful magnet. This steel pot directs the magnetic field lines downward to the contact surface. This causes the magnetic force to be concentrated at the contact surface and therefore increases the strength of the magnet. This strong adhesive force occurs only on direct contact with the counterpart. A pot magnet is not suitable for attraction over distance. For the best adhesive force the contact surface should ideally be a thick, smooth and unpainted surface.
Button magnets have a split adhesive surface. They are a non-shielded magnet made by a casting method. The poles in a button magnet are at each side of the magnet surface, separated by a groove. Because they are made from one piece of material, they are unaffected by differential expansion or contraction making them more suited to some higher temperature applications than pot magnets. It should be noted that they are not as powerful as the equivalent pot magnet but they do attract over a further distance.
U shape magnets have a high adhesive force with a split adhesive surface. As well as retaining purposes, they can be used for sorting and lifting. They are made using a casting method.
Raw magnets are unshielded magnets. They are suitable for almost universal use and are usually glued in place. An air gap increases their force, depending on the air gap between magnet and mating component, individual raw magnets can have a substantial adhesive force.
We also stock setting bolts and grub screws which incorporate a retaining magnet. These are ideal for uses such as a workpiece stop, with the magnet holding the workpiece in place. The locking nut can be used to secure the stop screw after positioning.