(a) 50 mm or more in diameter, shall be equipped with a guard compatible with the work being performed and offering the most efficient protection against accident;
(b) shall be tightened between 2 protective discs of a minimum diameter of at least 1/3 its diameter unless mounted on chucks cemented on back metallic plates or firmly fixed on back by any other mean;
(c) shall have its tool holder or its work stand firmly fixed and never more than 3 mm from the abrasive wheel;
(d) shall be inspected before being mounted in order to detect cracks, excessive looseness or other defects;
(e) shall not operate at a speed higher than the maximum speed specified by the manufacturer; and
(f) shall not be used if it is cracked, broken or unbalanced.