What can be indicated by black or blue discoloration on a drill bit?

Black or blue discoloration on a drill bit typically indicates wear from use. When a drill bit is subjected to high temperatures due to friction during drilling operations, it can undergo a process called tempering, which affects its hardness and appearance. The heat generated can cause the metal to oxidize, leading to a change in color. This signifies that the bit has been used extensively and may be losing its cutting effectiveness.

In the context of maintenance and inspection, recognizing this discoloration is crucial for determining when a drill bit should be sharpened or replaced to ensure optimal performance and safety during assembly operations. This is particularly important in aerospace applications where precision and reliability are paramount.