Always wear eye and ear protectors, and an apron to protect against sparks during operation. Ensure the disc is not contacting the work piece before the switch is turned on. Before using the machine on an actual work piece, let it run until it reaches full operational speed. It should run smoothly (i.e., with no vibration or wobbling). If it does not run smoothly, turn it off and check the attachment of the disc and the disc itself Don’t use cutting discs for surface grinding. Always use two hands to hold the grinder—one on the side handle and the other on the body of the grinder. Where possible have the job positioned so that the sparks travel away from the operator. Do not touch the work piece immediately after operation—it may be hot and could burn your skin.