digest
Short Summary
Main recommendation: sand evenly across the whole project with a random orbit sander, use rigid sanding blocks for edges and corners, and protect plywood veneer, because sanding mistakes are common and can ruin near-finished work. The video identifies five specific sanding mistakes, and it recommends treating sanding with the same care as cutting accurately.
Key Points
- The five mistakes are: (1) sanding uneven joints so one area is over-sanded and the board cups; (2) over-sanding edges and corners with a random orbit sander, which rounds corners or leaves bulges; (3) treating sanding as a spot procedure and neglecting wide faces, which causes finish imperfections later; (4) sanding through the thin veneer of plywood, especially hardwood plywood; (5) sanding too close to inside edges and leaving gouges from the disc edge.
- The disc flexes when pressed against a corner, concentrating force on a small area, which causes the disc to cup and produce bulges.
- Surface imperfections in neglected wide faces often do not show up until a finish is applied.
- Plywood is usually presanded, so it generally needs only light sanding.
Details Worth Noting
- Concrete instructions: When sanding uneven joints, make a pencil mark along the entire board and sand until it disappears evenly. To check flatness, he suggests using your table saw's table, which is probably the flattest surface in your shop.
- Concrete instructions: For tabletop edges and corners, use rigid sanding sticks instead of the random orbit sander; the video shows a paint can stirring stick with sandpaper attached using spray adhesive.
- Concrete instructions: Feel plywood for fuzziness and, if needed, knock down fibers with 120 or 220 grit sandpaper; never sand plywood coarser than 120 grit, and only sand lightly without holding the sander in one spot.
- Concrete instructions: Protect plywood edge-banding areas by applying painter's tape before sanding, and align edge banding flush from the start.
- Concrete instructions: Wipe off glue excess right away with a damp cloth when building with plywood; if dried glue remains, sand it with 120 grit carefully.
- Concrete instructions: For inside surfaces near edges, protect the edge with tape if prone to gouging, or avoid sanding that close and hand sand to the inside edges.
- The video notes that hardwood plywood veneers such as cherry or walnut are even thinner, making them easier to sand through.
- The video recommends that inside surfaces are usually secondary and a light sanding is often sufficient, with greatest attention on primary visible surfaces.
Bottom Line
Sanding errors often happen late in a project, so slow down, sand the whole surface evenly, switch to hand blocks at edges, and respect plywood's thin veneer.
