English: Milling cutter paused after taking a cut. Arrows show the vectors of various velocities collectively known as speeds and feeds. Circular arrow represents angular velocity of the spindle in rev/min, called the "spindle speed" by machinists. The tangential arrow represents the tangential linear velocity (m/min or sfm) at the outer diameter of the cutter, called the "cutting speed", "surface speed", or simply the "speed" by machinists. The arrow colinear with the slot that has been milled represents the linear velocity at which the cutter is advanced laterally (usually mm/min or inch/min for milling; may also be measured as mm/rev or inch/rev). This velocity is called the "feed" by machinists.