Read the number and suffix separately
In common sintered NdFeB designations, the N identifies the material family and the number relates to its maximum energy product, BHmax, usually expressed in MGOe. It is a material energy-density figure. It is not a number of kilograms, a surface-gauss reading or a force rating.[4]
| Designation | BHmax range | What still needs checking |
|---|---|---|
| N35 | 33–35 MGOe | Br, HcJ, temperature curves and part geometry |
| N42 | 40–42 MGOe | The same fields, under comparable conditions |
| N52 | 49.5–52 MGOe | Coercivity and thermal margin, as well as energy density |
Energy-product examples from K&J’s material specification table
N35
- BHmax range
- 33–35 MGOe
- What still needs checking
- Br, HcJ, temperature curves and part geometry
N42
- BHmax range
- 40–42 MGOe
- What still needs checking
- The same fields, under comparable conditions
N52
- BHmax range
- 49.5–52 MGOe
- What still needs checking
- Coercivity and thermal margin, as well as energy density
These are examples from one supplier’s data, not our available-grade list or a universal cross-reference. Other manufacturers may give different limits or use their own naming systems. Compare the numerical specification and test conditions behind a code.[3]
Letters such as M, H, SH, UH and EH usually distinguish coercivity or temperature classes within a supplier’s system. They do not add directly to the energy-product number. Obtain the relevant material sheet rather than treating a suffix as a complete thermal specification.[2]
M, H, SH, UH and EH: a reference, with conditions
Dura groups the following common suffixes by reference operating temperature, with an explicit length-to-diameter condition of L/D ≥ 0.7. This is a reading aid for that supplier’s table, not a guaranteed temperature for any shape or a list of our stocked grades.[2]
| Common suffix | Reference group temperature |
|---|---|
| M | 100°C; some high-energy M grades are grouped at 80°C or 90°C |
| H | 120°C |
| SH | 150°C |
| UH | 180°C |
| EH | 200°C |
Dura reference groups; L/D ≥ 0.7
M
- Reference group temperature
- 100°C; some high-energy M grades are grouped at 80°C or 90°C
H
- Reference group temperature
- 120°C
SH
- Reference group temperature
- 150°C
UH
- Reference group temperature
- 180°C
EH
- Reference group temperature
- 200°C
The M exceptions show why a suffix alone is insufficient. Read the full row, coercivity and temperature curves for the actual grade; check the circuit and opposing field before using the reference temperature in a design.
A higher grade does not settle the application
Consider two holding designs: a compact higher-grade magnet separated from steel by a plastic cover, and a larger lower-grade magnet sitting close to an appropriate steel target. A grade comparison alone cannot rank their holding performance. Volume, shape, magnetization, air gap and the return path all matter.
Likewise, a sensor may need a field within a particular window. Increasing the field beyond that window can make the design worse. Specify the required measurement and location before treating the highest available grade as the objective.
BHmax is found on the normal second-quadrant material curve. The application has its own operating point, which need not be the maximum-energy point. Read the property definitions and strength comparison guide when a drawing mixes grade, gauss and force.[5]
Keep temperature conditions attached to the grade
A suffix is a starting point for thermal selection. The maximum usable temperature also depends on geometry, magnetic circuit and opposing fields. Dura’s grade groupings explicitly attach a length-to-diameter condition to their reference temperature values. Arnold lists material properties and temperature information together; neither should be detached from its scope.[2] [1]
When comparing a high-energy grade with a higher-coercivity alternative, ask for the curves at the intended magnet temperatures. Check the hot-state function and the performance after cooling. The coating, adhesive and housing also need suitable thermal limits.
Turn a grade request into a specification
- Identify the manufacturer or supplier data sheet, revision and material route.
- Separate guaranteed minima from typical values and ranges.
- State geometry, finished dimensions, magnetization axis and surface treatment.
- Provide the operating temperature range, magnetic circuit and opposing-field conditions.
- Agree the sample and batch measurements that establish acceptance.
If the drawing already specifies N42SH, preserve that requirement in the inquiry. If the grade is undecided, describe the function and constraints. Confirm the actual proposed material before ordering. Detailed grade-to-grade comparisons and available supply grades remain separate decisions; this guide does not replace either.
Technical sources
Source material has its own scope and conditions. These references explain technical choices; they are not evidence of our stock, certifications or supplied products.