280 vs 320 Grit Sandpaper: Defect Removal or Final Scuff?

The choice between 280 and 320 grit often appears at the awkward point where a surface is almost ready, yet a few defects remain. Going straight to 320 can preserve control, but it can also waste time polishing around marks that still need removal. Staying with 280 cuts faster, but unnecessary passes may thin a film or soften detail. The right grade is the one that completes the current job without doing the next job prematurely.

Decide whether you are correcting or scuffing

Choose 280 grit for light correction: removing a uniform earlier scratch pattern, reducing small sanding marks, or leveling a minor defect on a material that permits it. Choose 320 grit for lighter refinement or scuffing after the surface is already level.

This comparison only holds when both abrasives use the same grading system and construction. Grit numbers from different standards, minerals, coatings, or backing types are not a controlled comparison. A fresh 320 sheet can cut more consistently than a clogged 280 sheet, and a powered sander can change the result relative to hand sanding.

A useful diagnostic is to mark each issue before starting:

• A low spot or remaining coarse scratch needs correction, not merely a finer haze.
• A uniformly dull surface that only needs the next approved scratch profile favors 320.
• A gummy film or rapidly loading sheet points to cure, heat, or compatibility—not a simple grit problem.
• A sharp edge that must remain sharp calls for firm support and minimal passes at either grit.

Give 280 a removal job

Use 280 when the evidence says material must still come off. On bare material, that may mean the previous abrasive lines are plainly visible under raking light. On a compatible coating, it may mean a small, fully cured imperfection can be leveled without breaking through the film. Always defer to the coating maker’s instructions; some products specify a preparation range, while others prohibit sanding at a particular stage.

Sand the defect only until it blends into the surrounding scratch pattern. Expanding the work area without a reason can create a shallow hollow. A block that spans the defect helps a flat surface stay flat, whereas pressing with a fingertip concentrates the cut and can leave a depression.

The 280-grit guide provides a broader look at where this grade fits. Here, its defining role is modest correction before the final scuff or refinement step.

Give 320 a surface-prep job

Use 320 when leveling is finished and you need a finer, even pattern. It is commonly considered for light surface preparation, small dust-nib cleanup, or smoothing an earlier pattern, but “commonly” is not authorization for every finish. Verify that the substrate and next product permit it.

If a defect remains after several clean, light passes with 320, stop. More time at a finer grit may polish the edges of the defect while leaving its bottom intact. Move back to the least aggressive grade that removes it efficiently, then re-establish the 320 pattern. The 320-grit guide explains that grade’s wider uses and limits.

Compare two small lanes before committing

Prepare an offcut or inconspicuous test area with the same surface history. Make one lane with fresh 280 and one with fresh 320. Use equal light pressure, equal coverage, and the same backing. Extract or remove dust using a method compatible with the surface.

Inspect both lanes under a movable, low-angle light. A successful 280 lane should remove the previous pattern without introducing random deep scratches. A successful 320 lane should produce an even, finer-looking pattern without leaving shiny low spots. If 320 leaves the defect and 280 removes it, the choice is clear. If both remove it, prefer the less aggressive 320 unless the specified next process says otherwise.

For a same-family trial, the catalog includes a 10-sheet 280-grit option and a 10-sheet 320-grit option. You can also review the 280-grit collection and 320-grit collection. These links identify catalog options; confirm current specifications, stock, and material compatibility yourself.

Control the variables that imitate grit differences

Change abrasive before it is badly loaded. Do not bear down to make a spent sheet cut. Keep the block flat, lift it before changing direction at an edge, and avoid lingering at the boundary of a repair. With power sanding, use the tool and extraction settings approved for the material and watch heat-sensitive surfaces closely.

Also clean between grades. A loose 280 particle trapped under a 320 sheet can produce a line that makes the finer grade appear ineffective. Use separate, clean work areas or at least clear the support pad and surface before switching.

Stop when the next process can succeed

The endpoint is not “as smooth as possible.” It is a continuous scratch pattern that the next approved operation can handle. If 280 achieves that, 320 may be optional. If 320 is specified, use it only long enough to replace the 280 pattern everywhere, then stop.

In practical terms, 280 is the correction-oriented choice and 320 is the restraint-oriented choice. Confirm that distinction on a sample, because the workpiece, abrasive family, and finish system ultimately decide how large the difference feels.