N = spindle speed, rpm s o = feed (tool), mm/rev n p = number of passes required Speed, N, is determined from cutting velocity, V C /min C 1000 DN Vm π = (4.9.3) where, D = diameter of the job before cut Therefore, 1000V C N D = π (4.9.4) The number of passes, n p is mathematically determined from, 1 p 2 DD n t − = 2 (4.9.5)

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