The surface grinding process for urban outdoor wooden furniture typically involves three distinct grades that transform rough lumber into weather-resistant finished products.
Rough grinding (Grade 1) begins with coarse 24-40 grit abrasives to remove significant imperfections, mill marks, and create initial surface leveling. This stage eliminates approximately 1.5-3mm of material and prepares the wood for subsequent processing.
Semi-finish grinding (Grade 2) utilizes 60-100 grit abrasives to smooth the surface further, removing scratches from previous grinding while maintaining enough tooth for adhesion of protective coatings. This intermediate stage ensures proper dimensional accuracy.
Finish grinding (Grade 3) employs fine 120-180 grit abrasives to create the final smooth surface ready for sealing. This critical grade determines the furniture's tactile quality and coating performance, with higher grit numbers (180-220) sometimes used for premium pieces requiring ultra-smooth surfaces.
The exact number of grades varies by manufacturer, with some incorporating additional polishing steps for luxury items. Proper progression through these grinding stages ensures outdoor furniture withstands urban environmental challenges while maintaining aesthetic appeal through years of exposure to sun, rain, and temperature fluctuations.