Maximum speed may be the worst speed

Scott Smith, a professor from the University of North Carolina at Charlotte, shares views on the conditions required to attain the machine's maximum spindle speed. A high-speed spindle usually has a smaller-diameter shaft than a conventional spindle because it is easier to get a small-diameter spindle to rotate at a high speed than a large-diameter spindle. The spindle is often the most flexible element in the system and the first spindle bending mode is the most flexible mode if the spindle diameter is small and the tool is short. The frequency of the mode is determined primarily by the diameter, length and material of the spindle shaft. The small amount of unbalance produces a variable force that excites the spindle at the rotational frequency with the rotation of the spindle. Machine tool users, especially those cutting materials such as aluminum, often select the highest spindle speed as the operating speed.