SPI Finish Standards
The SPI Finish Standards refer to the surface finish standard set by American SPI (Society of the Plastics Industry). The standard covers 12 SPI surface finish grades and features at:
- from SPI A1 to SPI D3 ( RA 0.012 μm to RA 18.00μm).
- from shiny to dull.
- from polish to texture.
At below SPI finish chart, we use surface roughness Ra (μm), finishing methods, steels suggested as references to show each grade’s finish.
If you want to check what the physical surface finish would look like, the best way is to get our SPI Finish Card.
| SPI Finish Standard | Surface Roughness Ra (μm) | Finishing Method | Fnishing Look | Steels Suggested |
|---|---|---|---|---|
| SPI A1 | 0.012 to 0.025 | 6000 Grit Diamond | Super High Glossy finish | S136 (54HRC) or 8407(52HRC) |
| SPI A2 | 0.012 to 0.025 | 3000 Grit Diamond | High Glossy finish | S136 (54HRC) or 8407(52HRC) |
| SPI A3 | 0.05 to 0.10 | 1200 Grit Diamond | Normal Glossy finish | S136 (300HB) or 718H |
| SPI B1 | 0.05 to 0.10 | 600 Grit Paper | Fine Semi-glossy finish | 718H |
| SPI B2 | 0.10 to 0.15 | 400 Grit Paper | Medium Semi-glossy finish | 718H |
| SPI B3 | 0.28 to 0.32 | 320 Grit Paper | Normal Semi-glossy finish | 718H |
| SPI C1 | 0.35 to 0.40 | 600 Grit Stone | Fine Matte finish | 718H |
| SPI C2 | 0.45 to 0.55 | 400 Grit Stone | Medium Matte finish | 718H |
| SPI C3 | 0.63 to 0.70 | 320 Grit Stone | Normal Matte finish | 718H |
| SPI D1 | 0.80 to 1.00 | Dry Blast Glass Bead | Satin Textured finish | 718H |
| SPI D2 | 1.00 to 2.80 | Dry Blast | Dull Textured finish | 718H |
| SPI D1 | 3.20 to 18.0 | Dry Blast | Rough Textured finish | 718H |
