Difficulty: Medium
Correct Answer: 1 to 3 m/min
Explanation:
Introduction / Context:
Thread grinding requires accurate lead control and crest-root definition. Because the form must be generated precisely by the wheel, job (workpiece) speed is kept low to maintain profile fidelity and minimize dynamic errors.
Given Data / Assumptions:
Concept / Approach:
Lower work peripheral speeds reduce chatter risk and thermal distortion while allowing finer control of the helical path relative to wheel form. Typical practice limits work speed to only a few metres per minute, while the grinding wheel runs at very high surface speeds.
Step-by-Step Solution:
Recognize the need for positional accuracy → choose conservative work speed.Typical data tables specify work speeds approximately 1–3 m/min for thread grinding.Therefore, select 1 to 3 m/min.
Verification / Alternative check:
Machine builders’ charts and shop handbooks list low work speeds for thread grinding compared with plain cylindrical grinding, which often allows higher job speeds.
Why Other Options Are Wrong:
Speeds above ~5 m/min increase risk of profile errors and chatter; 10–20 m/min are more typical of other grinding operations, not precision thread grinding.
Common Pitfalls:
Confusing wheel speed (very high) with workpiece speed (low); mixing recommendations for traverse cylindrical grinding with form grinding of threads.
Final Answer:
1 to 3 m/min
Discussion & Comments