Rotating Abrasive Wheel on a <a href="https://en.wikipedia.org/wiki/Grinding_machine" class="extiw" title="w:Grinding machine">Grinder</a>
Occupational Safety &amp; Health Administration (OSHA) part of the U.S. Department of Labor
<a rel="nofollow" class="external free" href="http://www.osha.gov/SLTC/etools/machineguarding/animations/grinder.html">http://www.osha.gov/SLTC/etools/machineguarding/animations/grinder.html</a>