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Ra Series Spec Table
Ra Series KS Specifications — 12 sizes
KS B ISO 4287
Surface roughness table organized by Ra (arithmetic mean roughness) value, with corresponding grade, process method, and application.
Practical Notes
- Smaller Ra = smoother and costlier. Seal surfaces Ra ≤0.8; fit surfaces Ra 1.6–3.2; general surfaces Ra 6.3–12.5.
KSRa Series
12 sizes| Ra Value | Type | Rz (μm) | Process | Symbol | Use |
|---|---|---|---|---|---|
| Ra 0.012 | Ra Series | 0.05 | Super Finishing, Lapping | ▽▽▽▽ | Precision , Surface |
| Ra 0.025 | Ra Series | 0.1 | Super Finishing, Lapping | ▽▽▽▽ | Precision Bearing |
| Ra 0.05 | Ra Series | 0.2 | Super Finishing, Grinding | ▽▽▽▽ | Precision Shaft, Sealing Surface |
| Ra 0.1 | Ra Series | 0.4 | Grinding, Honing | ▽▽▽ | Bearing Mating Surface, Cylinder Bore |
| Ra 0.2 | Ra Series | 0.8 | Grinding, Precision Turning | ▽▽▽ | Precision Fit |
| Ra 0.4 | Ra Series | 1.6 | Grinding, Turning, Milling | ▽▽▽ | Fit Surface, Sliding Surface |
| Ra 0.8 | Ra Series | 3.2 | Turning, Milling, Grinding | ▽▽ | General MachineMachined Surface |
| Ra 1.6 | Ra Series | 6.3 | Turning, Milling, Drilling | ▽▽ | General Machined, Bolt Hole |
| Ra 3.2 | Ra Series | 12.5 | Turning, Milling | ▽ | Non-friction General Surface |
| Ra 6.3 | Ra Series | 25 | Turning, Casting | ▽ | Rough Machined Surface |
| Ra 12.5 | Ra Series | 50 | Rough Turning, Casting | ~ | Non-functional Surface |
| Ra 25 | Ra Series | 100 | Casting, Forging | ~ | As-cast/forged |
Key Features
- Arithmetic mean roughness (Ra); average deviation of profile heights within measurement length
- KS B ISO 4287; 25-step standard series from Ra 0.012–50 μm
- Achievable Ra by process: grinding 0.1–1.6, turning 0.8–6.3, milling 1.6–12.5 μm
Key Applications
Seal surfaces (Ra ≤0.4), bearing shafts (Ra 0.8), sliding surfaces (Ra 1.6), general machined (Ra 3.2–6.3)
FAQ
Relationship between Ra and Rz?
Generally Rz ≈ 4×Ra. E.g., Ra 1.6 → Rz ~6.3. Ratio varies by machining method, so specify both for precision parts.