When choosing a method to machine, up cutting or down cut milling (climb milling) is decided by the conditions of the machine tool, the milling cutter and the application. However, it is said that in terms of tool life, down cut (climb) milling is more advantageous.
The difference in tool life
The difference explained
For up cut milling, the cutting edge of a face mill cutter enters a workpiece at 0mm depth of cut (contact point) and moves while rubbing the workpiece at first. Then, when it reaches a certain point, the cutting edge starts to machine the workpiece. The area between the contact point and the cutting start point is the area of rubbing, here the force acting on the flank face sharply increases, causing flank wear on the cutting edge as in the figure.
Meanwhile, for down cut (climb) milling, the width of cut at the point of entry is the thickest, and as such reduces this abrasive phenomenon that is generally a weak point of cutting tools. However, if the cutting edge is too sharp or the tool material is not tough enough then fracturing can occur. Note also that if the machine has backlash then the workpiece can tend to be pulled or tugged on entry and this can also cause fracturing of the cutting edge.