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N Grade Spec Table
N Grade KS Specifications — 12 sizes
ISO 1302
This specification follows ISO (International Organization for Standardization) standards. ISO ensures cross-border compatibility, making it ideal for multinational projects, export equipment design, and global parts procurement.
Surface roughness table classified by N1–N12 grade system, corresponding to Ra values per ISO 1302.
Practical Notes
- N1–N12 grades correspond to Ra values. N6=Ra 0.8, N7=Ra 1.6, N8=Ra 3.2, N9=Ra 6.3.
ISON Grade
12 sizes| Ra Value | Type | Rz (μm) | Process | Symbol | Use |
|---|---|---|---|---|---|
| N1 (Ra 0.025) | N Grade | 0.1 | Super Finishing | ▽▽▽▽ | Super Fine |
| N2 (Ra 0.05) | N Grade | 0.2 | Super Finishing | ▽▽▽▽ | Super Fine |
| N3 (Ra 0.1) | N Grade | 0.4 | Grinding | ▽▽▽ | Fine |
| N4 (Ra 0.2) | N Grade | 0.8 | Grinding | ▽▽▽ | Fine |
| N5 (Ra 0.4) | N Grade | 1.6 | Grinding | ▽▽▽ | Fine |
| N6 (Ra 0.8) | N Grade | 3.2 | Grinding·Turning | ▽▽ | General |
| N7 (Ra 1.6) | N Grade | 6.3 | Turning·Milling | ▽▽ | General |
| N8 (Ra 3.2) | N Grade | 12.5 | Turning·Milling | ▽ | General |
| N9 (Ra 6.3) | N Grade | 25 | Turning·Casting | ▽ | Rough |
| N10 (Ra 12.5) | N Grade | 50 | Rough Turning | ~ | Rough |
| N11 (Ra 25) | N Grade | 100 | Casting | ~ | As-forged |
| N12 (Ra 50) | N Grade | 200 | Casting·Forging | ~ | As-forged |
Key Features
- ISO 1302 N1–N12 grade system; each grade corresponds to specific Ra value (N7 = Ra 1.6, etc.)
- Concisely marked as drawing symbol; roughness specifiable by N-grade alone without Ra value
- One N-grade step = ~2× Ra; higher grade number means rougher surface
Key Applications
Legacy drawing compatibility (triangle symbol → N-grade conversion), international standard drawings, casting/forging surface grading
FAQ
What is the Ra value for N7 grade?
N7 = Ra 1.6μm. N1=Ra 0.025, N4=Ra 0.2, N6=Ra 0.8, N7=Ra 1.6, N8=Ra 3.2, N9=Ra 6.3, N10=Ra 12.5.