b'NICE WHEELSChoose the proper grinding wheel.By Christopher Tate a mold to achieve the desired shape.A vitrified wheel is formed under pressure and G rinding is a machining process found at almostthen baked at a very high temperature, which all shops. Some grinding operations, such asturns the bonding materialsfor example, claysnagging castings, grinding welds or bench grinding,to glass, giving strength and rigidity to the wheel. are relatively simple. Other grinding activities can beResinoid-bonded wheels use the same sort ofcomplex like those used to hold very close tolerancesabrasives with a softer resin bond that often is or machine difficult materials. Grinding has a broadreinforced with other materials like fiberglass range of applications in manufacturing. As with manyto add strength. Resinoid wheels can operate procedures, selecting the best tool is critical. at higher cutting speeds than vitrified wheels Although the cutting edges are much smallerand are less likely to fail, with uneven loading and arranged in a random order, grinding wheelsmaking resinoid wheels ideal for use on hand are cutting tools and perform the same job astools or machines, such as chop saws. Vitri-endmills, drills and turning tools. Whether snag- fied wheels hold their shape better and are ging castings or grinding gears, wheels are similar. stiffer than resin-bonded wheels, making them best suited for close-tolerance Abrasives work performed on rigid machine Grinding wheels are made from several typestools. Both kinds of wheels can of abrasive materials, from aluminum oxidethebreak and fragment during use, softest and most commonto diamond, whichbut vitrified wheels are more is the hardest and most expensive. Most wheelssusceptible to catastrophic are manufactured by mixing the abrasive materialfailure, which is another with a bonding agent and then placing the mix inreasontheytypically Grinding Wheel SafetyGrinding wheels can be dangerous. I have worked at two companies where people died as a result of catastrophic wheel failures. Eye and hand injuries are common with abrasive hand tools and bench grinders. It is imperative for everyone using grinding wheels or equipment to be thoroughly trained. Simple tasks like ringing wheels, using blotters, properly torquing wheel flanges, standing and working in safe zones and incorporating appropriate personal protective equipment are critical to maintain a safe environment. The Occupational Safety and Health Administration, the American National Standards Institute, wheel manufacturers and machine builders all have detailed publications that outline safety requirements for grinding wheels and machines.44SEPTEMBER 2020 GrindingWheels.indd 44 8/19/20 8:26 AM'