Symptoms
- Circular scratch patterns visible under raking light or finish
- Marks show up after staining even though the wood felt smooth
- Swirls deeper in some areas than others
- Sanding doesn't seem to be removing the marks, just adding new ones
Likely causes
- CommonSandpaper is worn or clogged with dustDull or loaded paper drags and scratches instead of cutting evenly.
- CommonSkipping sandpaper grits (jumping too far between coarse and fine)Coarse scratches from a lower grit aren't fully removed before moving to a finer one.
- PossibleExcess downward pressure while sandingPressing hard forces the sander to dig in unevenly instead of gliding.
- Less commonSanding pad worn out or unevenly seatedA worn or lopsided pad transfers uneven pressure across the sandpaper.
What to do
- Replace the sandpaper with a fresh sheet or disc of the correct grit; don't try to push through with worn paper.
- Work through a proper grit progression (such as 120, then 150, then 220) instead of skipping straight to a fine grit.
- Let the sander's weight do the work; use light, even pressure and let the pad glide rather than pressing down.
- Keep the sander moving continuously in overlapping passes rather than stopping in one spot, which digs in unevenly.
- Vacuum or blow off dust between grits so it doesn't get trapped and scratch the surface.
- Check the sanding pad itself for unevenness or wear and replace it if it no longer sits flat.
- Wipe the surface with a damp cloth and inspect under raking light before finishing to catch any remaining swirls.
Tools and parts
- Sander
- Assorted grit sandpaper
- Shop vac or tack cloth
Replacement sanding padSearch: “random orbital sander replacement pad”
When to call a pro
Not typically a professional job; a furniture refinisher can help if swirl marks show up after finish has already been applied over the flawed surface.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.