What we get asked, answered properly
15 topics across grade selection, manufacturing, supply and circularity. Written and maintained by Twin Pole — not generated, and not a substitute for looking at your actual design.
Reading an NdFeB grade code
What N42SH actually tells you, and what it leaves out.
The number is energy product in MGOe — N42 means a nominal (BH)max of 42 MGOe. Higher is more field per unit of volume, and that is where the marketing stops.
The letters are the part that decides whether your motor survives. They denote intrinsic coercivity, which is resistance to demagnetisation, and they map roughly to a maximum working temperature:
• (none) — up to ~80°C
• M — up to ~100°C
• H — up to ~120°C
• SH — up to ~150°C
• UH — up to ~180°C
• EH — up to ~200°C
• AH — up to ~230°C
Two cautions. Those ceilings assume a well-behaved magnetic circuit; the real limit depends on your operating point, not on the grade alone. And energy product and coercivity trade against each other, so N52 does not exist in EH — asking for the highest number in both columns is asking for a magnet nobody makes.
