A rigid grinding disc is a solid abrasive wheel used on its edge and face. It removes metal quickly and leaves a gouged, coarse surface, and it is the tool for taking down a heavy weld or dressing a rough edge.
A flap disc is overlapping abrasive cloth leaves. It removes material progressively and leaves a surface fit for painting, so it does in one step what a grinding disc plus sanding would take two. For dressing welds flush, it is almost always the better choice.
The questions welders ask
Do I still need grinding discs?
For heavy stock removal, yes — a flap disc used for that job wears out expensively. The practical arrangement is a grinding disc for the first pass on a large weld and a flap disc to finish, or a flap disc alone on anything modest.
Last reviewed 2026-08-14