Eye and hand injuries represent the most common types of injuries caused by using a grinding wheel. Most of the time, these injuries are caused by neglecting to observe proper safety procedures or inattention while the grinder is operating. If you follow safety rules, you can almost entirely eliminate accidents and injuries with today's safer grinding wheels. There are, however, a few things you need to look out for.
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A grinding wheel, properly mounted and used, is relatively safe. In operation, the outside of the wheel may rotate at speeds in excess of 60 mph. Improper mounting can cause the wheel to vibrate and come apart at high speeds. If the mounting is too tight or the grinding wheel mounting hole is too small or too large for the arbor, the wheel can break under pressure and at speed. Pieces of the fractured wheel can be flung off; they are responsible for most eye injuries associated with grinder accidents. Manufacturers recommend that you wear goggles and a face shield to protect your eyes. A face shield alone is not sufficient to protect from small particles that might ricochet up under the shield.
Wrong Wheel for the Job
Grinding wheels come in varying strengths and textures for different kinds of jobs. Relatively soft wheels are used to prevent burning or distorting expensive or high-grade steels. Harder wheels are used for grinding or sharpening high-strength steel like cutting tools and drill bits. Cutter grinding wheels are used for cutting steel casings, steel plate, rods or sheet metal. Using the wrong wheel can cause the wheel to wear too quickly and become unbalanced or fall apart. The metal being ground can be damaged and shed pieces of metal. If using a wet wheel, be sure to spin it dry afterward to prevent the coolant from breaking up the wheel.
Wrong Speed for the Wheel
Grinding wheels are rated for specific speeds. The maximum working speed for each wheel is printed on a tag that comes with the wheel. Know what speed your grinder operates at. If it is a variable-speed grinder, know how fast each setting spins the wheel and do not exceed the manufacturer's recommended speed for the wheel you have mounted.
Too much side pressure, especially on thin straight wheels. Most wheels can stand up to a lot of straight on radial pressure, but too much side pressure or heavy pressure can overheat the wheel and break it. Bumping or pounding on the grinding wheel as its turning is dangerous.
Failure to Use Safety Hood
Most modern grinders come with a clear plastic safety shield to deflect bits downward as they are ground off. The shield won't stop everything, but it is the first line of defense.
Poor Grinding Technique
Poor grinding technique can result in abrasions or injuries. Among the causes are failing to hold your work correctly or brace your work agains a proper work rest; grinding on the side of a wheel not designed for that purpose; pressing too hard; forcing the grind too quickly on a cold wheel; grinding too high above the wheel center; failing to use wheel washers; or accidentally contacting unguarded moving parts. You can also cause wheel failure or accidents by trying to reach switches or controls that are out of reach while grinding or reaching across the wheel to make adjustments or manipulate controls while the grinder is spinning.