most common cutting wheel profiles are Type 1, which is flat, and Type 27, which has a depressed center, or raised center hub — Fig. 2. Generally speaking, Type 1 wheels offer more versatility, especially when cutting profiles, corners, C channels, or anything that requires the operator to cut up and over two different planes of cutting surface. Because the entire cutting surface is flat, users can use more of the wheel for cutting with less possibility of the raised center hub interfering with the workpiece. Type 27 wheels, on the other hand, are ideal for getting into tight corners or overhangs, or for whenever the operator needs additional offset from the grinder to perform the cut. The depressed center of a Type 27 wheel provides the extra clearance sometimes needed to get the job done. THE AMERICAN WELDER That said, an operator must be careful not to plunge too deep into the cut, as the raised hub can interfere with the material being cut and ultimately compromise the structural integrity of the wheel. For this reason, it’s most often recommended to use Type 1 cutting wheels unless the application specifically requires the additional offset provided by a Type 27 wheel. While technique plays a major role in both the cutting speed and lifespan of the cutting wheel, the main factor behind a wheel’s cutting performance is the cutting grain used — Fig. 3. Selecting the Appropriate Grain There are three cutting grains commonly used in bonded abrasive cutting wheels: aluminum oxide, zirconia alumina, and ceramic alumina. Aluminum oxide wheels provide an aggressive cut out of the box, but immediately begin dulling from the first cut. Ceramic alumina grains self-sharpen and are the most resistant to heat, providing a consistently high cut rate and longer life. Zirconia alumina grains are harder and sharper than aluminum oxide grains and provide an excellent value. DECEMBER 2016 / WELDING JOURNAL 87 Fig. 2 — Type 27 wheels (left) are useful whenever an operator needs additional offset from the grinder to perform the cut, while Type 1 wheels offer more versatility for cutting profiles, corners, C channels, or anything requiring cutting up and over two different planes of surface. Fig. 3 — The cutting grain used is the main factor behind a wheel’s performance.
Welding Journal | December 2016
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