I found an old water pump, or actually, half of it.
Reused it to disc sander.
Idea in this video, is to show how to make an adapter that allows one to use angle grinder backings with diy disc sander. This makes possible to change backing harder, smaller or softer if needed. Sander runs at 2800-3000rpm speed. There's a typing mistake on the video, 5000 supposed to be 3000.