What Wheel Thickness to Use and When Generally speaking, thicker wheels last longer, but that increased durability comes at a price. Thicker wheels cut slower and generate more friction and heat through the cut — often discoloring the workpiece and requiring additional steps to finish. Always consider the material when selecting the best wheel for the job. On harder steels and alloys — such as armored steels, titanium, stainless, high-nickel alloys, and cast iron, which generate significant heat throughout the cutting process — it’s cost effective to upgrade to a cutting wheel that is more heat resistant. Zirconia alumina and ceramic alumina are good choices in these applications. Using Proper Technique Heat and pressure are the enemy of any abrasive product. The smoothest, fastest, cleanest cuts are performed by minimizing surface contact and heat. Minimizing heat and friction also help maximize wheel life. Never bump, drop, or use impact to enter the cut. Always enter the material from a corner or section with less surface area, and use even pressure and consistent motion through the cut. Let the wheel do the work — pushing too hard increases cut speed but also generates heat and friction, which ultimately reduces wheel life. Angle of approach matters. Round stock is considered by many the easiest to cut because the surface contact is the same no matter where the operator enters the material. However, when cutting angle iron, Ibeams, or square stock, start the cut on a corner where the material is the thinnest to reduce friction and produce a clean, straight cut. Understand the thickness of the material being cut and take care to plunge the wheel only as deep as necessary for the thickness of that material. This also will reduce heat and friction to extend product life and minimize binding. Safety Tips Cutting wheels should never be used without a guard that is properly rated for the size of wheel and mounted correctly per manufacturer instructions. Type 1 cutting wheels require the use of a two-sided guard that offers 180 deg of protection. Before mounting any cutting wheel, check that the maximum safe rpm rating on the wheel is higher than the maximum rpm rating of the tool being used. Using a wheel with an rpm rating lower than the tool, improper mounting or tool misuse compromises operator safety, as well as the safety of coworkers, and can result in serious injury. It’s recommended to let the wheel free-spin for 60 s prior to beginning a cut. This allows the operator to detect any balance or structural issues with the wheel prior to use. Finally, operators should ensure the cut line is as close to the clamping point as possible while still allowing enough room for the guard, the tool, and their hands. The further an operator moves from the fixed point or clamp, the more vibration will be transferred through the workpiece, which reduces wheel life and increases the risk of wheel failure. This can also make the wheel more difficult to control. The proper angle for holding the grinder depends on several variables, including workpiece size and orientation, tool size, and user comfort. Before cutting, bring the wheel to the workpiece with the grinder stopped and look for potential interference. When the operator has determined the most comfortable angle of approach, adjust the guard so it is positioned between the body and the workpiece. Giving some forethought to the overall size and thickness of the workpiece before cutting can help ensure the guard won’t interfere with the cut halfway through. As with any skill, practice makes perfect. It’s important to consult with a trusted abrasives manufacturer if there are questions about safety considerations, selection, or technique. DECEMBER 2016 / WELDING JOURNAL 89 WJ RICK HOPKINS (rhopkins@ weilercorp.com) is senior product manager, Weiler Abrasives Group, Cresco, Pa. For info, go to aws.org/adindex
Welding Journal | December 2016
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