Did you ever want to remove a nut or bolt that is rounded off? Remove a slotted screw that has a badly worn slot? Or, remove a Phillips head screw that is rounded out?
This is how it is done, and it probably works 90% of the time or more. All of my mechanics had a container of valve grinding compound among their tools. It used to come in a two-sided metal tin. I recently bought this one, and it came in a two-sided plastic container. One side has the coarse grind and the other fine grinding compound. The stuff is cheap from your local automotive parts place, or Amazon Prime.
I put my watch into the photo to show a perspective.
A magnetic door catch fell apart, and to fix it, I needed to remove two Philips head screws. They were old and had been abused, so I dipped just the tip of my screwdriver into the fine side, and that worked perfectly to remove the screws.
If you are busting a hex head bolt or nut loose, be sure to use a 6 point socket, never a 12 point. This tip added by Mike Cecchini.
I hope that you will find this to be useful.
Updated 17 Oct 2019