Surface Finish Guide
Ra values, N-grades, typical machining processes, and cost indicators. Click any two rows to compare them side-by-side.
| Ra (µm) | N-Grade | Profile | Typical Process | Application | Rel. Cost |
|---|---|---|---|---|---|
| 0.1 | N1 | Lapping, superfinishing | Gauge blocks, optical flats, precision bearings | ||
| 0.2 | N2 | Diamond turning, fine grinding | Precision shafts, optical mounts, high-speed spindles | ||
| 0.4 | N3 | CNC milling (fine), precision grinding | Sealing surfaces, bearing races, high-precision fits | ||
| 0.8 | N4 | CNC turning (fine), standard milling | Hydraulic cylinders, precision shafts, instrument housings | ||
| 1.6 | N6 | Standard CNC milling/turning | General machined parts, assembly interfaces | ||
| 3.2 | N8 | Rough milling, standard turning | Non-critical surfaces, structural parts | ||
| 6.3 | N9 | As-machined (rough) | Rough structural parts, non-contact brackets | ||
| 12.5 | N10 | Rough machining, sawing | Raw stock, non-functional surfaces |
Lapping, superfinishing
Gauge blocks, optical flats, precision bearings
Diamond turning, fine grinding
Precision shafts, optical mounts, high-speed spindles
CNC milling (fine), precision grinding
Sealing surfaces, bearing races, high-precision fits
CNC turning (fine), standard milling
Hydraulic cylinders, precision shafts, instrument housings
Standard CNC milling/turning
General machined parts, assembly interfaces
Rough milling, standard turning
Non-critical surfaces, structural parts
As-machined (rough)
Rough structural parts, non-contact brackets
Rough machining, sawing
Raw stock, non-functional surfaces
How to specify surface finish
On engineering drawings, surface finish is specified as the Ra value in µm (e.g., Ra 1.6). For CNC machined parts, Ra 1.6 µm is considered the default "standard" finish unless otherwise specified. Always call out critical surfaces with explicit Ra requirements — our team will select the appropriate process accordingly.