Question 34 QMED05 - Machinist-Pump Technician

The Correct Answer is B. **Explanation for Option B (be cut crooked on the work):** When cutting external threads (like on a rod or bolt) using a hand die, the die must be started perfectly perpendicular (straight) to the axis of the work. The initial rotation of the die establishes the path for all subsequent threads. If the die is started at an angle, the cutting edges will bite into the material unevenly, resulting in threads that follow the initial angular path. This means the threads will be cut crooked, or out of square, relative to the workpiece axis. **Why the other options are incorrect:** * **A) be rough, weak, and easily broken:** While starting the die crooked can *contribute* to slightly rougher threads due to uneven pressure, the primary and immediate defect is the crookedness itself. Roughness and weakness are more often caused by dull tools, lack of lubrication, or cutting too fast, not just the starting angle. * **C) straighten out after the third revolution:** Once the threads are started crooked, the die will continue to follow that initial path, as the already cut threads act as guides. The threads will not spontaneously straighten themselves out. This defect is permanent and requires the threads to be machined off and recut properly. * **D) be out of round on the work:** "Out of round" (or ovality) means the thread diameter is not uniform around the circumference. Starting the die at an angle affects the squareness or straightness of the thread path relative to the work axis. Unless the work itself was already out of round, the finished threads will likely still be circular, but they will be leaning or angled, not truly perpendicular to the workpiece face.