• # question_answer The ratio between two consecutive spindle speeds for a six-speed drilling machine using drills of diameter 6.25 to 25 mm size and at cutting velocity of 18 m/min is: A) 1.02                             B) 1.32C) 1.06                             D) 1.82

${{\phi }^{5}}=\frac{25}{6.25}=4$ $\phi =1.32$