Tooth Counter

Photograph the gear face-on

1. Lay the gear flat on a plain surface that contrasts with it — a sheet of white paper under a dark gear, or dark cloth under bright steel.
2. Hold the tablet straight above it so the gear looks round, not oval.
3. Fill most of the frame, but keep the whole gear in the picture.
4. Avoid hard glare; diffuse overhead light works best.
5. For a rack, lay it across the frame with the teeth clearly visible, and keep the whole toothed length in the picture.
6. The app traces the part's outline first and only counts once that outline is confirmed against the photo.