Peripheral wear determines tool life
The image shows a simple drawing depicting the wear of a drill's cutting edge. The generation and the amount of wear differ according to the workpiece materials and cutting conditions used. But generally, the peripheral wear is largest and determines a drill tool life. When regrinding, the flank wear at the point needs to be ground away completely. Therefore, if there is large wear more material needs to be ground away to renew the cutting edge.
We: Chisel edge wear width
Wf: Flank wear width (The middle of the cutting edge)
Wo: Outer corner wear width
Wm Margin wear width
Wm': Margin wear width (Leading edge).