N35 Neodymium Ring Magnet 20mm Diameter - Specs & Local Availability

Key specifications to check

• Grade: N35 (higher grade numbers indicate greater maximum energy, but mechanical fragility increases with grade).
• Outer diameter: 20 mm; Inner diameter (bore): commonly 6 mm or 8 mm - confirm specific SKU.
• Thickness/height: typical 2-5 mm variants - affects pull force and field shape.
• Coating: nickel-copper-nickel (Ni-Cu-Ni) is common for corrosion resistance; verify if uncoated or epoxy-coated for wet environments.
• Operating temperature: standard N35 can demagnetise at elevated temperatures; check maximum operating temp (often ~80 degreesC) for your application.

Specification comparison

Selection guidance & compatibility

Choose the specific 20 mm ring magnet variant based on three primary factors: mechanical fit (inner bore and thickness), magnetic performance (grade and thickness determine pull force), and environment (coating and operating temperature). For sensor applications, align the pole face so the field at the sensor meets the required flux density - small changes in distance dramatically change the reading.

Simple calculation & example

Exact pull-force calculations require vendor data or finite-element analysis. As a rule of thumb, doubling thickness roughly increases pull force significantly; halving air gap between magnet and ferrous plate increases the flux coupling substantially. For quick planning, assume a 20 mm x 3 mm N35 ring on a flat 6 mm steel plate might produce a holding force on the order of 1-4 kg under ideal contact (estimate only). In South African projects, budget for higher-than-estimated forces when designing latches or motor couplings.

Mounting and wiring diagram (ASCII)

  Shaft or screw through bore
      |
  [===]  <--- 20 mm ring magnet (face towards sensor or plate)
   |||
  ----  <--- mounting plate or wheel

Place hall sensor ~1-5 mm from magnet face; adjust for expected switching point.

Safety, handling & troubleshooting

• Fragility: neodymium magnets are brittle. Use soft jaws or protective spacers when fitting to shafts to avoid chipping.
• Pinch hazard: magnets of this strength can snap together - handle with care and keep away from electronics that can be disrupted by strong fields.
• Demagnetisation risk: avoid exposure to temperatures above the specified rating or strong opposing fields.
• Interference: keep magnets away from magnetic storage, credit cards, and sensitive sensors unless designed for the application.

Local buying notes for South Africa

Communica stocks a range of magnets and small hardware suited to makers, students, and engineers. Typical price ranges for a single 20 mm N35 ring magnet are approximately ZAR 15-60 per piece depending on bore, thickness, and coating; actual pricing varies and is indicative only. Check the Samrand branch for the deepest component stock; alternate branches may have limited quantities or lead times. For education and institutional purchases, request a VAT invoice and quote through account services if required.

Accessory bundles & common pairings

• Fixings: M3/M4 countersunk screws and nylon spacers to secure ring magnets without cracking.
• Protective options: epoxy-coated magnets for higher humidity or plated variants for corrosion resistance.
• Sensors: Hall-effect switches and linear hall sensors for position or RPM sensing.

Sources

• Neodymium magnet - Wikipedia
• Neodymium magnet properties and grades - technical reference
• Magnets category - Communica