40x20x5mm Neodymium BAR Magnet

Specifications

• Dimensions: 40mm (Length) x 20mm (Width) x 5mm (Thickness)
• Material: NdFeB (Neodymium Iron Boron)
• Shape: Rectangular Bar
• Plating: Triple Layer Ni-Cu-Ni (Nickel-Copper-Nickel) for enhanced durability and rust resistance
• Magnetization Direction: Through the thickness (5mm faces are North/South)
• Max Operating Temperature: 80°C (176°F)

Applications

• Industrial Automation: Activating heavy-duty Hall Effect sensors across wide air gaps.
• DIY & Prototyping: Embedded latches for 3D printed cases, tool holders, and quick-release mechanisms.
• Motor Construction: Building custom axial flux generators or DIY brushless motors.
• Physics Experiments: Magnetic levitation and eddy current demonstrations.

Unlock New Capabilities

• Past Projects: You've probably used standard 10mm disc magnets for basic crafts, fridge notes, or tiny sensor triggers.
• Feature Upgrade: Upgrading to this massive 40x20x5mm block unlocks true mechanical load-bearing capabilities. It provides enough flux density to hold heavy tools or trigger magnetic switches reliably through thick acrylic or wood panels.
• Effort/Requirements: Beginner to Intermediate. All you need is some high-strength two-part epoxy or a custom CAD-designed sleeve to lock it into place.

SAFETY WARNING: Neodymium magnets of this size are incredibly strong and brittle. Do not let them snap together from a distance, or they will shatter and send sharp shrapnel flying. Slide them apart, never pull. Keep away from pacemakers, magnetic media, and sensitive unshielded electronics.

• Mounting Best Practices: Do not attempt to drill or machine this magnet it will break and the heat will destroy its magnetic properties. Secure it using structural adhesive (like epoxy) or design a snug 3D-printed pocket for friction/press-fitting.

Included in the Box:

• 1× 40x20x5mm Neodymium Bar Magnet

Frequently Asked Questions

• What is the exact size of this magnet?
  It measures 40mm in length, 20mm in width, and 5mm in thickness.
• What material is this magnet made from?
  It is made from NdFeB (Neodymium Iron Boron), which is a rare-earth metal compound known for its extreme magnetic strength.
• Is this magnet suitable for triggering Hall effect sensors?
  Yes, it creates a very strong magnetic field that can trigger Hall effect sensors like the A3144 even across wide air gaps or through non-magnetic barriers.
• Can I drill a hole in this neodymium magnet?
  No. Neodymium magnets are extremely brittle. Drilling or machining them will cause them to shatter and the heat generated will permanently destroy their magnetism.
• What is the maximum operating temperature?
  This standard grade neodymium magnet operates safely up to 80°C (176°F). Exceeding this temperature will result in irreversible loss of magnetism.
• Will it lose its magnetism over time?
  Under normal conditions (below 80°C and away from strong opposing magnetic fields), neodymium magnets lose a negligible fraction of a percent of their strength over 10 years.
• How should I glue this magnet to plastic or metal?
  Use a high-quality two-part epoxy or strong cyanoacrylate (super glue) after cleaning both surfaces with isopropyl alcohol.
• Is the plating corrosion-resistant?
  Yes, it features a triple-layer Ni-Cu-Ni (Nickel-Copper-Nickel) plating that provides a smooth finish and excellent resistance against moisture and corrosion.
• What happens if two of these snap together?
  They will accelerate towards each other with immense force and likely shatter or chip upon impact. Always slide them apart rather than pulling, and handle multiple magnets with extreme care.
• How strong is the pull force of a 40x20x5mm magnet?
  While exact pull force depends on the contacting material and surface thickness, a magnet of this size can typically hold several kilograms of direct vertical weight against solid steel.
• Can I use this for a DIY wind turbine generator?
  Yes, rectangular neodymium blocks are commonly used in the rotors of DIY axial flux alternators and wind turbines due to their strong, flat magnetic fields.