Recommended cutting speed for HSS on mild steel For machining a mild steel workpiece using a high-speed steel (HSS) tool under typical shop conditions, which average cutting speed is most appropriate?
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A5 m/min
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B10 m/min
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C15 m/min
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D30 m/min
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E60 m/min
Answer
Correct Answer: 30 m/min
Explanation
Introduction / Context:Cutting speed selection is central to tool life and productivity. For HSS tools cutting mild steel, shop handbooks provide ranges that balance wear, heat, and finish. Too low wastes time; too high burns the edge.
Given Data / Assumptions:
- Tool: HSS (uncoated), standard geometry.
- Material: mild steel (~0.15–0.25% C).
- Conventional coolant and feeds; average conditions.
Concept / Approach:Typical speeds for HSS on mild steel are around 25–35 m/min for turning, depending on rigidity, coolant, and depth of cut. Values like 5–15 m/min are excessively conservative and uneconomical; 60 m/min is more suited to coated carbides.
Step-by-Step Solution:
Consult typical HSS speed charts for mild steel.Identify common midrange recommendation near 30 m/min.Select 30 m/min as the reasonable average speed.Verification / Alternative check:Machining handbooks and shop experience confirm acceptable tool life and finish near 30 m/min with HSS on mild steel.
Why Other Options Are Wrong:5, 10, 15 m/min: needlessly slow, poor productivity unless under severe constraints.60 m/min: typically too fast for HSS on mild steel; risk of rapid wear.
Common Pitfalls:Ignoring feed and DOC interactions; failing to adjust speed for interrupted cuts or poor coolant delivery.
Final Answer:
30 m/min