Quick check
Table search
Filter the table by size, symbol, process, value, or application without scanning the whole chart.
Mechanical design reference
Surface Roughness Chart
Search typical Ra, Rz, and Rt surface roughness values for machining and finishing processes used on engineering drawings and manufacturing plans.
Design reference
Search surface roughness chart
Use the searchable table to filter the reference data by the values, symbols, sizes, and applications that matter for your design check.
Quick check
Design check
Use the table for early sizing and drawing checks, then confirm final values against the governing standard.
Reference table
Typical surface roughness by process
| Process / Finish | Ra (µm) | Rz (µm) | Rt (µm) | Notes |
|---|---|---|---|---|
| Turning (fine) | 0.8 | 6.3 | 7.9 | Single-point cutting tool, light feed |
| Turning (medium) | 1.6 | 12.5 | 15.8 | Standard lathe finish |
| Milling (fine) | 1.6 | 12.5 | 15.8 | Face milling or end milling, fine cutter |
| Milling (medium) | 3.2 | 25.0 | 31.5 | Standard rough milling |
| Grinding | 0.4 | 3.2 | 4.0 | Surface grinder, precision finish |
| Polishing | 0.1 | 0.8 | 1.0 | High gloss, mirror finish |
| Lapping | 0.05 | 0.4 | 0.5 | Ultra-precision finishing |
| Sandblasting | 3.2-6.3 | 25-50 | 31-63 | Textured surface, decorative or functional |
| Shot Peening | 1.6-3.2 | 12.5-25 | 15.8-31.5 | Improves fatigue resistance |
How to use
Practical checks for surface roughness chart
Unit conversion
mm = in × 25.4
Use this for inch-to-metric conversions where the page includes dimensional data.
Clearance check
clearance = hole size - feature size
Positive clearance helps confirm whether a part can assemble freely.
Tolerance range
range = upper limit - lower limit
The usable manufacturing window is the difference between upper and lower limits.
Documentation check
value + unit + standard
Reference data is most useful when paired with units and the governing drawing or design standard.
Definitions
What the reference values mean
Reference Value
A tabulated value used for selection, comparison, or early design checks.
Nominal Size
The named or target size before manufacturing tolerance is applied.
Tolerance
The allowed variation from the nominal or specified value.
Standard
The source convention or governing document that defines how a value should be interpreted.
FAQ
Surface Roughness Chart questions
How should I use this table?
Use it for quick comparison, preliminary design, drawing review, and shop reference.
Can this page replace the governing standard?
No. Use this page as a fast reference; final design and inspection should follow the current standard, drawing notes, and project requirements.
Why is the table searchable?
Search helps you jump directly to a size, symbol, process, value, or application without scanning every row.
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