Hi all. I just recently bought an Angle Grinder. And needed some sanding discs. Saw the ad from Northern. Decided to give them a try. Fast shipment. Used the disc on my very first project. A Clutch Spring Compressor for a Yamaha Majesty. Made quick work of the coating on the steel plate. So I could paint. Tool came out real nice.
Flap discs are great to use with your grinder to put an edge on tools with heavier blades - like lawn mower blades, hedge clippers, loppers, etc. I put an edge on any lawnmower blade so that it's sharp from both sides.
Any tool that cuts with "scissors-like" action has one blade that's essentially fixed and the other blade cuts by the motion of a knife edge. I sharpen both blades of everything that cuts like scissors the same (sharpen the outside edges of both blades only; and whatever is taken off of one blade has to be removed from the other)