The cutting length is affected by the position of the milling cutter. Tool life is often related to the length of cutting that the cutting edge must bear. The milling cutter positioned in the center of the workpiece has a short cutting length. If the milling cutter is offset from the center line in either direction, the cutting arc is long.
Keep in mind how the cutting force works and must achieve a compromise. With the tool positioned in the center of the workpiece, the direction of the radial cutting force changes as the cutting edge of the blade enters or exits the cutting. The gap in the machine tool spindle also exacerbates the vibration, causing the blade to vibrate.
By deviating the tool from the center, a constant and favorable cutting force direction is obtained. The longer the overhang, the more important it is to overcome all possible vibrations.
Another advantageous effect of a constant machining allowance is the small adverse effect on the machine tool, the guide rails, the ball screw and the spindle bearings.