One potential source northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba of serious injury in grinding comes from an oversight that is easy to make: operating the wheel in an over-speed condition. While a wheel that is run far enough in excess of its rated maximum speed may shatter within minutes of operation, danger may also result from a wheel run just slightly faster than its rated speed. This less severe over-speed condition can cause the wheel to be damaged, and the damage northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba may result in breakage after further use. For example, operating a reinforced, 9-inch diameter, Type 27 wheel northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba rated for a maximum speed of 6,600 rpm on a 7-inch angle grinder with a speed of 7,700 rpm can cause the wheel to crack. northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba This northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba cracking can lead to breakage later. Any of these actions sets up a disastrous scenario that could lead to northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba an accident involving serious injury or death.

Danger comes from the fact that centrifugal force does not increase in direct proportion to an increase in speed, but instead it increases as the square of that speed increase. When rotational speed doubles, northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba centrifugal force quadruples. This effect means that relatively small changes in speed can produce significant increases in force. In the example mentioned, changing from 6,600 rpm to 7,700 rpm multiplies the speed by 1.167. However, the corresponding centrifugal force would multiply by a factor of 1.167 x 1.167, or 1.36. To take a more extreme example, consider the same wheel with a maximum safe operating speed of 6,600 rpm run on a 5-inch right angle grinder at 10,000 rpm. This represents an over-speed of about 1.5 times the wheel''s designed speed. But the corresponding centrifugal force-and the corresponding rotational stress on the wheel-would be about 2.3 times as much as the maximum allowed.

In short, never over-speed a grinding wheel. The speed of the grinder must be compared to the speed marked on the wheel or package to make sure the machine''s speed is at or below the maximum operating speed of the wheel. Surpassing this rating risks not just wheel breakage but also the safety of shop personnel. About the author: Roger Cloutier is a senior product safety northernindustrialtoolssandblastergunwithbrassvalvenozzlemodelatsb803aba engineer for the Norton Abrasives brand of Saint-Gobain Abrasives in Worcester, Massachusetts.

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