A reaming operation produces finish tears. What is the cause of these tears?

The presence of finish tears during a reaming operation is often attributed to the condition of the reamer itself. When a reamer has a worn tip, it can no longer maintain the precise cutting edge needed to cleanly finish the surface of the material being worked on. A worn cutting tip can lead to inadequate shearing of the material, causing it to tear rather than be smoothly cut. This results in a rough surface finish characterized by tear marks, rather than the desired smooth finish.

While other factors, such as cutting speed, reamer size, and lubrication, can contribute to surface quality issues, a worn tip directly affects the tool's ability to perform its function effectively by compromising the cutting action. Thus, recognizing and maintaining the condition of the reamer is critical to achieving the intended surface finish in machining operations.