12 x 9 x 4mm Neodymium BAR Magnet

Specifications

• Material: Neodymium-Iron-Boron (NdFeB) Rare Earth Magnet
• Shape: Block / Bar
• Dimensions: 12mm (Length) x 9mm (Width) x 4mm (Thickness)
• Dimensional Tolerance: ±0.1mm to ±0.2mm
• Grade: N35 (Standard High-Strength)
• Plating/Coating: Ni-Cu-Ni (Nickel-Copper-Nickel) Triple Layer for corrosion resistance
• Magnetization Direction: Through the thickness (4mm dimension - large flat faces are the poles)
• Max Operating Temperature: 80°C (176°F)

Applications

• Non-Contact Sensing: The perfect companion for Hall Effect sensors (like A3144) or Reed Switches to detect door closures, RPM, or limit stops on linear actuators.
• 3D Printing & Enclosures: Embed them mid-print into PLA/PETG designs for invisible, high-strength magnetic latches on project boxes.
• Robotics: Creating removable payloads, quick-swap end effectors, or magnetic tracks for miniature rovers.
• DIY & Crafting: Heavy-duty tool organizers, custom display stands, and high-end magnetic closures for leathercraft or bookbinding.

Unlock New Capabilities

• Past Projects: If you've been relying on mechanical microswitches or physical latches that wear out over time...
• Feature Upgrade: this high-strength magnet unlocks solid-state mechanical design. By pairing this with a Hall sensor, you can build frictionless limit switches for CNCs or 3D printers that never degrade.
• Effort Level: Beginner. Requires basic understanding of polarity and standard adhesives (cyanoacrylate/superglue) for mounting.

CRITICAL HANDLING WARNING:

• Neodymium magnets are extremely powerful and inherently brittle.
• Do Not Let Them Snap: Allowing two magnets to jump and snap together from a distance will cause them to chip, shatter, or produce dangerous flying shards. Slide them apart, do not pull.
• Heat Sensitivity: Do not solder or weld directly to the magnet. Exceeding 80°C will permanently destroy its magnetic properties.
• Electronics & Health: Keep away from pacemakers, magnetic ID cards, hard drives, and sensitive analog electronics.

Included in Package:

• 1 x 12x9x4mm Neodymium BAR Magnet

Frequently Asked Questions (FAQ)

• What is the pull force of this 12x9x4mm magnet?
  While exact pull force depends on the contacting material and surface area, a magnet of this size and N35 grade typically provides around 1.5kg to 2.5kg of direct pull force against a thick, flat steel plate.
• Where are the North and South poles located?
  The poles are located on the two largest flat faces (12x9mm surfaces). The magnetization is directed through the 4mm thickness.
• Can I cut or drill into this magnet?
  No. Neodymium magnets are extremely hard and brittle. Attempting to drill or cut them will cause them to shatter and will also generate highly flammable dust.
• Will this magnet rust?
  The magnet has a triple-layer Ni-Cu-Ni coating to prevent oxidation. However, if the coating is scratched or chipped, the inner NdFeB material will rust quickly, especially in humid environments.
• Can I use this magnet outdoors?
  It is not recommended for prolonged outdoor exposure unless completely sealed (e.g., encased in plastic or epoxy) because moisture can penetrate micro-cracks in the coating and cause rusting.
• What is the maximum temperature this magnet can handle?
  The maximum operating temperature for standard N35 neodymium magnets is 80°C (176°F). Exceeding this will cause irreversible loss of magnetic strength.
• How do I safely separate two of these magnets?
  Do not try to pull them straight apart. Place them on the edge of a table and firmly slide the top magnet sideways off the bottom one.
• Is this magnet strong enough to trigger a Reed Switch through plastic?
  Yes, this magnet produces a strong enough field to reliably trigger a standard glass reed switch through 3-5mm of standard ABS, PLA, or acrylic.
• What kind of glue should I use to mount this magnet?
  Cyanoacrylate (Super Glue), two-part epoxies (like Araldite), and strong double-sided tapes (like 3M VHB) work best. Ensure the magnet surface is clean and dry before applying.
• Will this magnet interfere with my Arduino or Raspberry Pi?
  It will not affect the digital processing of microcontrollers, but it will interfere with analog magnetic sensors, compass modules (like the HMC5883L), and older magnetic storage devices.
• Can I embed this magnet inside a 3D print?
  Yes! You can pause your 3D print, insert the magnet into a designed cavity, and resume printing to completely encase it in plastic. Ensure the cavity has a tiny bit of tolerance (e.g., 12.2 x 9.2 x 4.2mm).
• Why did my magnet lose its strength after a few weeks?
  Permanent magnets do not naturally lose strength over a short time. This only happens if they were exposed to temperatures over 80°C, extreme physical shock, or a strong opposing magnetic field.