# Polishing

> Progressive abrasives down to mirror: the finish for optics, molds and show surfaces.

- Process group: Mechanical Finishes
- HTML page: https://fabvector.com/finishes/polishing (Portuguese: https://fabvector.com/pt/finishes/polishing)

## Specifications

| Spec | Value |
|---|---|
| Coating thickness | No coating — removes 5–20 µm through progressive abrasives, reaching Ra 0.05–0.4 µm mirror to near-mirror. On clear PMMA and PC it restores optical transparency to machined faces. |
| Tolerance impact | Subtractive: 5–20 µm comes off the polished faces, and hand-guided polishing slightly rounds sharp edges and can soften small details. Precision features need removal allowance or masking — flag mirror callouts at quote time so they enter the program. |
| Corrosion rating | Slightly improved — a smoother surface offers fewer crevice initiation sites, but no coating is added; corrosion behavior remains essentially that of the base material. |
| Appearance | Mirror to near-mirror brightness (Ra 0.05–0.4 µm depending on grade); on clear plastics, polished faces turn optically transparent instead of frosted-machined. |
| Applicable substrates | aluminum, stainless-steel, steel, titanium, copper-alloys, invar-36, polycarbonate, acrylic-pmma |

## Not suitable for

Parts that must keep sharp functional edges — polishing rounds them (cutting edges, sealing lands, knife-edge seals); deep narrow slots and internal pockets the polishing media cannot reach; budget parts where bead blasting or as-machined already satisfies the spec (polishing is labor-intensive and priced accordingly).

## Typical applications

- Optical mold cores and cavity faces
- Medical instruments and cleanable surfaces
- Transparent PMMA / PC windows and light guides
- Premium cosmetic show faces before plating