It is expressed in units of distance across the workpiece surface per unit of time, typically surface feet per minute (sfm) or meters per minute (m/min). Each, however, can also be considered and analyzed in its own right.Ĭutting speed (also called surface speed or simply speed) is the speed difference ( relative velocity) between the cutting tool and the surface of the workpiece it is operating on. They are often considered as a pair because of their combined effect on the cutting process. The phrase speeds and feeds or feeds and speeds refers to two separate velocities in machine tool practice, cutting speed and feed rate. This velocity is called the "feed" 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). 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 circular arrow represents the angular velocity of the spindle (rev/min), called the "spindle speed" by machinists. Arrows show the vectors of various velocities collectively known as speeds and feeds. Photo of a milling cutter during a cutting operation. Most CNC lathes have constant surface speed to counteract that natural decrease, which speeds up the spindle as the tool plunges in. Notice that as the tool plunges closer to the workpiece's center, the same spindle speed will yield a decreasing surface (cutting) speed (because each rev represents a smaller circumferential distance, but takes the same amount of time). The "feeds" may be for the X-axis or the Z-axis (typically mm/rev or inch/rev for lathe work sometimes measured as mm/min or inch/min). Its tangential linear equivalent at the workpiece surface (m/min or sfm) is called the " cutting speed", " surface speed", or simply the " speed" by machinists. The angular velocity of the workpiece (rev/min) is called the " spindle speed" by machinists. Two separate velocities in machine tool practice, cutting speed and feed rate A line drawing showing some basic concepts of speeds and feeds in the context of lathe work.
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