ForMatter/Finishes/polish/DA 320-grit prep
finish_polish_da_320

DA 320-grit prep

polish · satin · dual-action prep, DA-sanded, 320-grit DA

The pre-paint surface — a uniform, matte, slightly toothy texture from a dual-action random-orbital sander. Not a finish you'd display; a finish you'd paint over. Auto bodywork, prepped boat hull, MDF before primer.

Random-orbital sanding (combined rotary + orbital motion eliminates cut lines) with 320-grit aluminum-oxide or silicon-carbide paper on a soft pad. Ra ~3 µm typical — coarse enough that primer keys mechanically, fine enough that the pattern doesn't telegraph through paint. Step often preceded by 180 / 220 grit to flatten, followed by 400 / 600 grit only if the topcoat is direct-to-metal.

character — uniform matte, slightly toothy, paint-ready, never a final state.

Finish properties

  • levelsatin
  • subcategoryDA-prep
  • Ra (µm)3.0
  • applies tometal, wood, polymer, composite

Second life

reversibilitymoderate — a polished surface can be re-roughened (sandblast, brush, etch) and a roughened surface can be re-polished; the substrate is preserved unless polishing-induced material loss is significant.
blocks substrate recyclingno
renewabilityvery high — polishing is the canonical maintenance operation for almost any hard surface; field-renewability is high for accessible surfaces, shop-renewability for everything else.

ASM Handbook Vol. 5 Surface Engineering; manufacturer abrasives literature (3M, Norton, Mirka).

Citations