Orbital sander: common mistakes and how to avoid them

Learn to use an orbital sander correctly so you get a smooth finish without swirl marks or gouges.

OS-01Pick the right sandpaper gritSandpaper grit is a number that tells you how coarse or fine it is. Low numbers like 60-80 are coarse and strip off paint or level rough wood. High numbers like 180-240 are fine and give a smooth finish ready for paint or varnish. The beginner mistake is grabbing one sheet and using it for everything, which either takes forever or leaves the surface too rough.

1 pack · Sandpaper sheets, mixed grit pack (60-240)

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OS-02Fit the sandpaper onto the sander padMost orbital sanders have a hook-and-loop pad, like a giant strip of Velcro, so the paper just presses on and peels off. Line up the small holes in the paper with the holes in the pad, otherwise dust extraction won't work and dust will build up under the paper, making it bumpy. Press down firmly all over so the paper is flat and doesn't lift at the edges.

OS-03Start the sander before it touches the woodHold the sander with both hands and switch it on in the air, just above the surface, then lower it gently. If you switch it on already resting on the wood, it can jump or dig in and leave a mark you can't easily sand out. Lift it clear before switching off for the same reason.

OS-04Move it in slow, overlapping passesKeep the sander flat on the surface and move it steadily, slightly overlapping each pass like mowing a lawn. Let the weight of the tool and the spinning pad do the work; don't press down hard. Pressing hard or tilting the sander onto one edge is the classic mistake and it causes swirly scratch marks or uneven dips.

OS-05Work through the grits in orderStart with a coarser grit to remove the roughness, then move up to a medium grit, then a fine grit. Skipping straight from coarse to fine leaves deep scratches from the coarse paper that the fine paper can't remove. Wipe away dust with a cloth between grits so you can see the surface clearly.

1 each · Tack cloth or lint-free cloth

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OS-06Check you've done it rightRun your hand flat over the surface with your eyes closed; it should feel smooth with no ridges, bumps or scratchy patches. Then hold the piece at an angle to a light source, such as a window or lamp, and look along the surface; any swirl marks or shiny low spots will show up clearly this way. If you find marks, go back over that spot with the same grit you just used, not a finer one.

OS-07Wear eye and lung protection, and manage the dustSanding throws fine dust into the air, so wear safety glasses and a dust mask, especially with old paint that may contain lead in homes built before 1960. Most sanders have a small dust bag or can connect to a vacuum; empty or check it regularly, as a full bag stops suction and lets dust clog the paper. Never sand old paint dry without a mask if you're unsure of its age or content.

1 pack · Disposable dust masks (FFP2 or better)

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1 each · Safety glasses

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