Submarine propellers made for the U.S. Navy start from a metal casting having a 20-ft diameter. From start to finish, production of one of these 55-ton propulsion units requires 12 months. One reason the process takes so much time is the machining, which removes nearly 14 tons from a single propeller casting. "Such a time-consuming process may soon be a thing of the past," says Tony Schmitz, a National Institute of Standards and Technology engineer. He points out that NIST tool-wear and surface-finishing experiments led to a better understanding of the parameters of high-speed machining. He also indicates that the discoveries enable an increase in material removal during machining by a factor of ten. Refinements in the tool's path reduce the roughnes of the milled propeller surface, eliminating much of the final hand finishing required for smoothing blade surfaces. For more information, go to www.nist.gov.
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