A grade name like N42SH looks like a secret code, but it follows one simple rule used by every NdFeB supplier. Read it in two parts: the number is the strength, the letters are the heat resistance.
The number: strength
The number tells you how strong the magnet is. N35, N42, N48, N52 - the bigger the number, the stronger the magnet. "42" means the magnet stores about 42 units of magnetic energy (megagauss-oersted, MGOe). For everyday buying: higher number = stronger magnet.
The letters: heat resistance
The letters after the number tell you how much heat the magnet can take. They run from N (normal) up to TH (top high):
| Letter | Max working temp (approx.) |
|---|---|
| N (no letter) | 80 °C |
| M | 100 °C |
| H | 120 °C |
| SH | 150 °C |
| UH | 180 °C |
| EH | 200 °C |
| TH | 230 °C |
Approximate values per GB/T 13560-2017; shape also affects the real limit.
Reading examples
- N35 - 35 strength, no letter: a general-purpose workhorse for room temperature.
- N42H - 42 strength, H series: strong and moderately heat-resistant.
- N50SH - 50 strength, SH series: high strength plus good heat tolerance - common in automotive.
- N38EH - 38 strength, EH series: extreme heat resistance at moderate strength.
The trade-off
You cannot have maximum strength and maximum heat resistance in one magnet. The hottest grades are built on lower base strength, and they cost more. So do not automatically buy the biggest number - buy the smallest number that does the job at your temperature. For the full table of grades and values, see the Grade Data page.
Read on: magnets and heat → · describing your magnet to a supplier →