What angle should a tool bit for cutting an American National thread be ground at?

• A. 45 deg.
• B. 90 deg.
• C. 60 deg.
• D. 30 deg.

Answer: (C)

The tool bit for cutting an American National thread should be ground at an angle of 60 degrees. This angle is specifically chosen because American National threads are formed with a 60-degree profile, which aligns with the geometry of the thread and helps ensure precise cutting.

By using a 60-degree angle, the cutting edge of the tool matches the peak and valley structure of the thread, allowing for effective engagement with the material being cut. This results in smoother finishes and better dimensional accuracy of the threads produced. The 60-degree angle is standard across various threading practices, making it crucial for achieving the desired torque and grip characteristics of the American National thread design.