80 vs 100 Grit Sandpaper: Start Coarse Without Overcutting

Choosing 80 or 100 grit is a coarse-sanding decision with real consequences. Both can remove material quickly, but 80 leaves a more pronounced scratch pattern and consumes the work budget faster. One hundred grit offers more restraint, yet it may be inefficient when a durable coating or pronounced milling mark genuinely needs removal.

The short answer

Start with 100 grit when the defects are shallow, the part is thin, the edges matter, or you are unsure how quickly the surface will cut. Move to 80 only when a test shows that 100 is not removing the unwanted layer efficiently and the substrate can safely tolerate the coarser pattern.

Use 80 for a defined removal job, such as reducing substantial roughness on suitable bare material or stripping a compatible coating under an approved process. Use 100 for controlled initial smoothing, moderating an 80-grit pattern, or starting where unnecessary removal would be costly.

The comparison must stay within one abrasive family and grading system. Numbers alone do not standardize mineral, backing stiffness, coating density, tool speed, or pressure. A fresh 100-grit sheet can cut more predictably than a clogged 80-grit sheet, while a powered machine can make either grade far more aggressive than hand sanding.

Protect the work budget

The work budget is the amount of material, coating thickness, edge definition, and dimensional accuracy you can afford to lose. Before sanding, identify which of those is the limiting factor.

A solid, oversize board may have room for correction. Thin veneer, molded detail, a crisp arris, plated metal, and an unknown coating may have almost none. Sanding is not a discovery method for hazardous or unidentified layers. If an older coating may contain lead or another hazard, stop and use the applicable testing, containment, respiratory-protection, and disposal requirements instead of dry-sanding first and asking later.

For a deeper treatment of the individual grades, see the 80-grit removal guide and the 100-grit control guide. This comparison focuses on selecting the safer starting point when either number seems plausible.

Run a timed patch test

Use an offcut or a small inconspicuous area with the same surface history. Draw several light pencil lines only if pencil is safe for the substrate and easy to remove. With a flat block and fresh 100 grit, make a short, fixed number of light coverage passes. Clean the area appropriately and inspect under low-angle light.

If 100 removes the target marks steadily while preserving flatness, stay with it. If it barely affects a known-safe, removable layer, repeat the test beside it with fresh 80 using the same support, pressure, and coverage. Choose 80 only when the improvement in removal is clear and its deeper pattern can be removed within the remaining work budget.

Do not keep increasing pressure on 100 to imitate 80. That concentrates the cut, increases heat, and makes deep random scratches more likely. The grade should do the cutting while the block controls the geometry.

Account for the recovery sequence

Starting at 80 creates a recovery obligation. The next grade must remove the entire 80-grit pattern before finer refinement begins. If the part cannot tolerate that additional removal, 80 was too coarse even if it stripped the surface quickly.

Change the sanding direction slightly between stages where the material allows it. Under raking light, the older lines remain distinguishable until the next grade replaces them. Clean the workpiece, block, and surrounding bench before changing grades; one loose 80-grit particle can score the 100-grit stage.

For a small comparison, the catalog lists a 10-sheet 80-grit option and a 10-sheet 100-grit option. The 80-grit collection and 100-grit collection provide related choices. These are catalog references, not material or safety approvals; confirm specifications and current stock before use.

Keep flats flat and edges crisp

Use a firm block that spans the defect on broad flat surfaces. A loose sheet under a fingertip cuts a narrow hollow and makes the coarser grit seem faster for the wrong reason. Work up to an edge with reduced pressure rather than rolling over it. Masking an adjacent face may improve awareness, but tape is not a substitute for control and can itself affect delicate finishes.

Check progress often. Stop if the substrate becomes visible unexpectedly, a veneer changes color, an edge loses definition, heat builds, or the abrasive loads rapidly. Those signals call for diagnosis, not more passes.

Choose the least aggressive effective start

Eighty grit is justified when 100 cannot perform a confirmed removal job efficiently and the part has enough material for the deeper pattern and its recovery. One hundred grit is the better default when both grades work, because it preserves more of the surface and shortens the path to refinement.

The decisive evidence is the test patch: removal rate, scratch depth, flatness, and remaining work budget. Start no coarser than that evidence requires, and leave the surface as soon as the unwanted layer is gone.