How to Use Sandpaper and Files for Smooth Model Finishes

By Dollfie — VOLKS USA, INC. | Published: 2026-10-25

Category: How-to Guides

Learn the correct order and technique for using sandpaper and files to remove seams, smooth plastic, and prep models for painting.

Quick answer

Start with a file to remove large material, then switch to progressively finer sandpaper grits to erase scratches and leave a smooth surface.

Why start with a file instead of sandpaper

Files remove material faster and more precisely than sandpaper on raised seams or thick sprue nubs. A medium double-cut file leaves visible scratches, but those scratches are uniform and easy to erase with the next grit of sandpaper. Skipping the file and starting with sandpaper wears out sheets quickly on heavy material.

When to switch grits

The goal is to replace deep scratches with finer ones until the surface feels smooth to the touch. A jump of no more than two grit levels (for example, from P400 to P600) avoids leaving scratches that the next sheet cannot remove. Moving too fast creates extra work.

Step-by-step sanding process

Remove excess material with a file: Use the flat file on straight seams and the half-round file on curved sections. File in one direction (not back-and-forth) to avoid gouging plastic. Stop when the seam is flush. Do not over-file; you only need to remove the raised seam, not reshape the part.
Start sanding with the coarsest grit that removes file scratches: For most plastic kits, P400 or P600 Tamiya Finishing Abrasive will erase file marks in a few light strokes. Sand in a circular motion to avoid creating new straight scratches. If the file scratches remain after ten passes, step down to a coarser grit (e.g., P400) instead of pressing harder.
Progress through finer grits without skipping: Move to P800, then P1000, then P1200 or P1500. Each step should take less time than the previous one because the scratches are already shallow. Wipe the part clean between grits to prevent trapped debris from scratching the surface. A common mistake is skipping straight to a fine grit; the old scratches will still be visible under paint.
Finish with ultra-fine grit for a polish-ready surface: Use P2000 or the Ultra Fine set to remove the last visible scratches. The surface should feel smooth and look slightly matte. At this stage the part is ready for primer. Do not sand the same area longer than necessary with ultra-fine grit—it can burnish the plastic and reduce paint adhesion.

Products that help

TAMIYA Basic File Set (Medium Double-Cut): The TAMIYA Basic File Set includes flat, round, and half-round files in a compact 16 cm length, designed for plastic and soft metals. The three profiles let you reach flat panels, curved surfaces, and inside corners without buying separate tools.
TAMIYA Basic File Set (Medium Double-Cut)
Tamiya Finishing Abrasives: Tamiya Finishing Abrasives come in grits from P400 to P2000, plus Fine and Ultra Fine sets, with each sheet measuring 93 × 226 mm. The wide grit range lets you progress from heavy scratch removal to final polish without switching brands or buying separate packs.
Tamiya Finishing Abrasives