Pretty sure most angle grinders I own turn in a direction, so the rotation keeps the wire wheel, flap disk, wafer wheel or whatever you use, tight and further tightens it. Problems for me happens when a wafer wheel explodes definitely don't have the strength or grip anymore to turn the collar alone. Harbor freight and other 4.5" grinders are pretty inexpensive so being a self proclaimed tool junkie I have acquired a handful of 4.5" grinders leaving specific grinding wheels on each one all the time. I use a cordless grinder specifically for wafer wheels and cutting some steel. Cuz it's really nice keeping a power cord out of the way when making cuts at odd angles or cutting seized bolts or pins.