The goal of sanding
Sanding removes a thin layer of material so the surface is flat, uniform and ready for finish. Each grit of sandpaper leaves scratches, and the next, finer grit is meant to replace those with smaller ones. Good results come from removing the scratches of the previous grit completely, not from rushing to a fine paper or from pressing harder.
Prepare before you start
Wear eye protection, hearing protection and a good dust mask or respirator, since sanding dust is fine and can irritate the lungs. Some wood dust is considered more harmful than others, and the manual and the material’s safety information are worth checking. Unplug a corded sander, or remove the battery from a cordless one, before changing paper.
Check the surface first. Set protruding nail heads below the surface, scrape off dried glue, and wipe away dirt. Dried glue resists stain and sands unevenly, so remove it before sanding, not after. Make sure the paper is the right type for your sander, fits the pad securely, and lines up with the dust holes if the pad has them. If you need background on the machines themselves, the differences between types of sanders explain why an orbital, a sheet sander and a belt sander behave differently.
Choose a grit progression
Grit numbers go up as the paper gets finer. A typical sequence for bare wood runs something like 80 or 100 grit for removing marks, then 120, then 150 or 180, and finally 220 for a smooth surface ahead of a finish. Exact choices depend on the wood, the starting condition and the finish. Some points to keep in mind:
- Start with the finest grit that will actually remove the flaws. Beginning too coarse creates deep scratches that take many steps to remove.
- Avoid jumping too far between grits. Skipping one step is often acceptable, but a big jump leaves scratches that the finer paper takes a long time to erase.
- Do not sand finer than needed. Very fine sanding can burnish the surface and keep stain from soaking in evenly, which is one cause of blotchy stain on some woods.
- Stop at the grit recommended for your finish. Oil and water-based products can call for different final grits, so check the can.
Choosing the right paper is partly about sandpaper grit and partly about material. The abrasive types, such as aluminum oxide and silicon carbide, behave differently on wood, paint and metal.
Use light pressure
The weight of the sander is usually enough. Pressing down slows the pad’s motion, heats the paper, clogs it faster, and can leave deep swirl marks or flat spots. It also puts load on the motor. Hold the sander flat on the surface with both hands where the design allows, and let the abrasive do the cutting. If the paper is not cutting, change it rather than pressing harder.
Keep the sander moving
Place the sander flat on the work before switching it on, and switch it off only after lifting it clear, or follow the manual’s guidance for your model. Starting or stopping with the pad tilted can gouge the surface. Move at a slow, steady pace, overlapping each pass by roughly half the pad width. Staying in one place creates a dip. Take particular care at edges and corners, where a tilted pad rounds them off.
Random orbital sanders leave fewer visible scratches because the pad moves in a random pattern, but they can still mark the wood if you press hard or hold the tool at an angle. Sheet and belt sanders work best going with the grain. Reading the grain before you start helps you avoid cross-grain scratches, which show up strongly under a clear finish.
Control the dust
Dust control makes the work more comfortable and gives better results, because dust trapped under the pad can scratch and clog the paper. Use the dust bag or connect the sander to a vacuum if it has a port. The benefits of a dust collector go beyond cleanliness, as fine dust that stays in the air is a health concern. A shop vacuum is useful for quick cleanup between grits, which also keeps coarse grit from being carried onto finer paper.
Work in a ventilated space and, where possible, consider an air filter. Wiping the surface with a cloth, a tack cloth or a slightly damp rag between grits shows any remaining scratches and keeps the surface clean. Raking light, from a lamp held low across the surface, helps reveal them.
Inspect before moving on
Before going to the next grit, look at the whole surface in good light. Mark light pencil lines across the area and sand until they disappear; if some remain, the sanding has missed spots. This simple check is a helpful guard against a surprise after stain goes on.
Know when to switch to hand sanding
Power sanders have trouble in tight corners, profiles and small detail. Wrap paper around a block or use a flexible pad by hand. Hand sanding with the grain is also the best way to remove faint cross-grain marks at the end. When you move to finishing, between-coat sanding follows the same general idea, using a fine abrasive and a very light touch.
Quick checklist
- Prepare the surface and fit the right paper.
- Start with the grit that suits the condition.
- Work with light pressure and steady, overlapping passes.
- Clean up dust between grits.
- Check for leftover scratches before changing paper.
- Finish with hand sanding where needed.