The strongest permanent magnets commercially available are typically composed of Neodymium Iron Boron (NdFeB). This rare-earth composition generates an incredibly high attractive force, known as tensile strength. This immense magnetic pull makes direct separation of two bonded magnets exceedingly difficult and potentially hazardous because it requires overcoming the full, direct magnetic bond. This article provides practical, physics-based methods for safely overcoming this powerful force.
Leveraging Shear Force Through Sliding and Twisting
The fundamental principle for safe separation involves converting the high tensile force (pulling straight apart) into a much lower shear force (sliding parallel to each other). It is significantly easier to separate magnets using the sliding motion because the magnetic field strength drops off rapidly as the magnets move out of alignment.
The most common technique is the sliding method, which should be performed on a stable, non-metal surface like a wooden workbench or plastic tabletop. Hold one magnet firmly while pushing the other magnet sideways, keeping it in contact with the surface.
For powerful magnets, the edge of a table can be used for leverage. Place the bonded magnets on the surface with one magnet overhanging the edge. By pressing down on the magnet resting on the table and pushing the overhanging magnet downwards, you create a slight air gap and then slide it away. For cylindrical magnets, a slight twisting motion can be introduced before the slide to break the initial direct surface contact. Once separated, move the magnets quickly and far apart to prevent them from magnetically “jumping” back together.
Mechanical Aids and Dedicated Separation Tools
When manual sliding is insufficient for larger or exceptionally strong magnets, mechanical aids are required to create a controlled air gap. Wedging is an effective technique that uses non-ferromagnetic materials like plastic, brass, or wood to physically push the magnets apart. Stronger magnets require thicker spacers to effectively reduce the magnetic field.
Specialized magnetic separators or custom non-magnetic jigs can be employed to stabilize the magnets and control their movement during separation. These devices often incorporate a lever or screw mechanism to apply gradual, controlled force, which is safer than relying on sudden manual effort. A wooden dowel or a non-magnetic pry bar can also introduce the initial separation gap when wedges are difficult to insert.
For industrial cases, devices like a workbench vise or clamping system made of non-ferrous materials can hold one magnet steady while a lever acts on the other. Extreme temperature changes, such as heating, can temporarily weaken a magnet’s field, making separation easier. However, exceeding the magnet’s maximum operating temperature, often around 80°C (176°F) for standard grades, can permanently demagnetize it or damage its protective coating.
Critical Safety Precautions and Storage
Handling powerful magnets requires strict adherence to safety protocols to mitigate the severe risks of injury. The most immediate threat is the pinch hazard, where the immense force of the magnets snapping together can cause crush injuries to fingers and skin. Wearing protective gloves is a standard precaution. Eye protection, such as safety glasses, is also necessary because NdFeB magnets are brittle and can shatter upon high-speed collision, sending sharp fragments flying.
The strong magnetic field can interfere with sensitive electronic and medical devices. Magnets must be kept a safe distance, often at least 12 to 18 inches, from items such as:
- Credit cards
- Hard drives
- Cell phones
- Pacemakers or other implanted medical equipment
For long-term safety, magnets should be stored correctly. They must be kept separate from each other using non-magnetic spacers made of materials like wood, plastic, or sturdy cardboard. Stacking magnets with a spacer prevents the powerful attraction that makes future separation difficult. Alternatively, a ferromagnetic steel plate, known as a keeper, can be placed across the poles of a magnet to contain the magnetic field, reducing its external reach and making the magnet safer to store near other items.