Is stock removal your primary objective, or do you want a smooth finish? Choosing the right disc shape is the single-most important variable, and the shape will help you effectively achieve your results. Flap discs are almost always used on right angle grinders, and they are applied to your work at an angle or parallel to it. Flap discs are available in two shapes: conical or flat-shape.
Conical flap disc: Conical flap discs are your best friends when you need to remove a lot of material in a small amount of time. They can be used for edge-working as well as on contoured applications. The flaps in a conical flap disc are angled. As a result, these discs offer a greater surface area for stock removal on horizontal surfaces.
Flat flap disc: While conical discs are great for rapid stock removal, flat flap discs are best for blending and superior finishing. They are mostly used on flat surfaces. The flaps of a flap disc are adhered to a backing plate which provides stability during operation.