What can happen if you use a sandpaper grit that is too coarse for the surface?

Using a sandpaper grit that is too coarse for the surface can indeed cause more damage or scratches. Coarse grit sandpaper is designed to remove material quickly and aggressively, which can result in a rough surface with deep scratches. This is particularly problematic when preparing surfaces for painting, as it can lead to an uneven texture that may negatively impact the adhesion of paint.

Additionally, a rough surface can create problems with the final appearance of the finish; it may lead to an inconsistent application of paint and could require additional sanding or work to correct the damage. Fine grit sandpapers are more appropriate for smoothing surfaces and providing a better substrate for paint application, as they minimize imperfections rather than exacerbating them. This understanding of grit sizes and their appropriate applications is crucial for achieving a professional-quality finish in painting and refinishing work.