The amount of power required to remove one cubic inch of material from the workpiece during a machining operation, measured in horsepower per cubic inches per minute. Unit power, also known as specific cutting energy, is a material property but is also affected by the type of machining operation and the material and sharpness of the cutting tool. Values for unit power are typically in the range of 0.1-2.5 hp/in^3/min (most steels have a value of 1.0-1.5 hp/in^3/min).