Grit tells you how coarse or fine a sanding sheet is, and it controls how fast you remove material and how smooth the surface looks. Lower numbers are coarse and remove material quickly. Higher numbers are fine and leave a smoother surface. Working through grits in order gives the best results.
Reading the Numbers
Grit numbers refer to the size of the abrasive particles. A low number means large particles that cut deep scratches. A high number means tiny particles that leave faint ones. Labels vary a little between makers and regions, so check the packaging.
| Grade | Typical use |
|---|---|
| Coarse | Shaping and removing old coatings |
| Medium | Smoothing rough surfaces |
| Fine | Preparing for a finish |
| Very fine | Light smoothing between coats |
Working Through the Grits
- Begin with the coarsest grit needed to fix the surface problem.
- Sand evenly, following the grain on wood.
- Wipe away dust so loose particles do not scratch.
- Move up to the next grit, not skipping too far ahead.
- Finish with a grit that suits the coating you plan to apply.
Why Skipping Grits Causes Trouble
Each grit removes the scratches left by the one before. If the jump is too large, deep scratches from the earlier step may stay and show up under a finish. Smaller steps take a bit more time but give a more even look.
Other Things That Matter
- Sheets clog with dust, so change them before they stop cutting.
- Even pressure helps avoid dips and uneven spots.
- Wear a dust mask and eye protection, as the maker advises, and manage dust following local rules.
- Different materials, such as metal, wood or drywall, call for different abrasive types.
Hand Sanding and Power Sanding
The same grit rules apply whether you sand by hand or with a machine, but power sanders remove material faster. With a machine, keep it moving and avoid resting on one spot, since it can leave dips. With a block, wrap the sheet around it so pressure stays flat and even.
Check your progress by wiping the surface and looking at it from a low angle under good light. Scratches from a coarser grit show up clearly. If you can still see them, go back over the area with the grit you just used before moving on.
Abrasive Materials Compared
Grit size is only half of what a sanding sheet or disc is. The mineral on the surface also changes how it cuts and how long it lasts. Aluminum oxide is a common general-purpose abrasive and is widely used on wood and metal. Silicon carbide is sharp and often chosen for sanding between finish coats, paint, plastics and some metals, though it can wear faster on bare wood. Ceramic abrasives are marketed for heavy removal and long life and are usually found on discs and belts for power tools. Garnet is a natural abrasive that some woodworkers like for hand sanding bare wood. Check the packaging to see which mineral is used and what the maker says it suits.
Backing matters as well. Paper backings are light and flexible, cloth backings resist tearing and suit curved or heavy work, and film backings are used where very even scratch patterns are wanted. Some sheets are coated with a stearate or similar additive to reduce clogging, which is useful on paint and finishes but may not suit every job. Open-coat sheets have gaps between the grains to give dust room to escape, while closed-coat sheets are covered more fully and cut faster on hard surfaces. If the packaging does not explain these terms, look at the maker’s guide before choosing.
Choosing a Starting Grit for the Job
The best starting grit is the coarsest one you actually need, not the coarsest one you own. Starting too coarse leaves deep scratches that take many steps to remove, while starting too fine wastes time on a surface that needs real work. A useful test is to try a spot on scrap or an out-of-sight area and see how quickly the surface improves.
- Removing old paint, heavy mill marks or shaping: begin coarse.
- Smoothing planed or machined wood: begin medium.
- Preparing wood for clear finish: finish with fine grit, following the finish maker’s advice.
- Scuffing a coating so a new coat will stick: a fine or very fine grit is often enough.
- Smoothing drywall compound: use sheets made for drywall and a fine grit, with attention to dust.
Hardwoods and softwoods respond differently. Softwoods can scratch and dent easily, so heavy coarse sanding is rarely needed. Dense hardwoods may need a little more effort to reach the same smoothness but can be polished to a fine finish. Read the instructions for the stain, paint or oil you plan to use, since some say not to sand too fine before application.
Sanding Between Coats and Before Finishing
Finishing adds its own sanding needs. Before the first coat, the surface should be even and free of dust. Many finishes raise the grain of wood by wetting the fibers, leaving a slightly rough feel after the first coat dries. A light pass with a fine sheet knocks those fibers down. Some woodworkers also wipe a damp cloth over bare wood and let it dry before the last sanding step, so the raised grain is dealt with before the finish goes on.
Between coats, the goal is different. You are not removing material but lightly scuffing the surface to give the next coat something to grip and to level small dust nibs. Use a very fine sheet, light pressure and let the finish dry fully first. Sanding a coating that is still soft will gum up the sheet and may damage the finish.
After each pass, remove dust completely. A vacuum with a brush attachment followed by a clean, slightly tacky or lint-free cloth is a common routine. Check what the finish maker recommends for wiping, because some solvents can affect certain coatings. Taking time on this step saves you from trapping dust under the next layer.
Discs, Sheets and Fitting Your Sander
Machine sanders use sheets cut for their pad shape, and compatibility is not universal. A random orbital sander takes round discs, often with a pattern of holes for dust extraction. The hole pattern should line up with the pad for dust collection to work, so match the disc to the pad. A palm sander uses a rectangular sheet cut from a larger one or sold pre-cut. Belt sanders need belts of the correct length and width.
Attachment types differ too. Hook-and-loop discs press onto the pad and are easy to swap, but the pad’s hooks wear out over time and discs begin to slip or fly off. Adhesive-backed discs stick more firmly but are harder to change. Clamp-style sanders use sheets held by clips and need paper cut to size.
Before you buy a pack, check the size and attachment against your sander’s manual. Buying in assorted grit packs is practical for varied jobs, and it helps to keep different grits stored flat and labeled so you do not grab the wrong one mid-project. Replace a worn pad if discs no longer hold, and never use a disc with a damaged or out-of-round edge, since it can vibrate or catch.
Troubleshooting Common Sanding Problems
When a surface looks wrong after sanding, the cause is often traceable. Swirl marks from a random orbital sander usually come from pressing too hard, tilting the pad, or using a worn or clogged disc. Slow down, use lighter pressure, keep the pad flat and change the disc. Cross-grain scratches on wood show up especially under stain, so sand with the grain for the final steps, even when a machine is leaving fine random marks.
If paper clogs quickly, the surface may be damp, resinous or coated with something that is gumming the sheet. Let the material dry, switch to a sheet designed to resist clogging, or clean with a rubber-type cleaning block if the maker allows. If the sheet seems dull but you cannot see why, remember that dust buildup can feel like a loss of cutting power.
Low spots and dips are usually caused by dwelling in one place or by soft backing under the paper. Use a firm block for flat surfaces, and check progress with a straightedge. Safety remains important: wear eye protection and a dust mask suited to the dust, and keep fine dust from piling up, since some dusts are hazardous or combustible. Follow your sander’s manual and local rules for disposal.
FAQ
Can I use one grit for everything?
You can for light jobs, but most projects look better when you move from coarse to fine in steps.
Does finer grit always give a better result?
Not always. Some finishes need a little surface texture to grip, so check the instructions for your coating.
How do I know when a sanding sheet is worn out?
It stops removing material quickly, the surface feels smoother than the grit suggests, or the sheet looks shiny, clogged or torn. If you press harder to get the same result, change the sheet instead.
Should I sand wood before or after wiping it with a damp cloth?
Many people do a light wipe after the near-final sanding step to raise the grain, let it dry, and then make a last fine pass. Check the finish instructions, as some suggest a different order.
Can I wash and reuse sandpaper?
Some cloth or film backed abrasives may be cleaned, but paper sheets usually are not designed for it. Follow the maker's note, and replace a sheet that has lost its cut.
Is wet sanding different from dry sanding?
Yes. Wet sanding uses water or a suitable lubricant and sheets made for it, and is common on finishes and some metals. Use only products labeled for wet use, and keep water away from electric tools.
Why do my sanded surfaces look blotchy after staining?
Scratch patterns, uneven sanding, leftover dust or glue residue can all cause blotching. Sanding evenly through your grit steps and cleaning thoroughly usually helps, and test the stain on scrap first.
What grit should I use on bare wood before oil or varnish?
It depends on the product and the wood, so check the finish maker's guidance. Many people stop in the fine range and test on a scrap piece to see the look they want.
The Short Version
Low grit numbers remove material fast, high numbers smooth it. Work up through grits in order, clear dust between steps, and follow the maker’s directions for your tool and coating.