Difficulty: Easy
Correct Answer: chilled cast iron
Explanation:
Introduction / Context:
The lathe bed must provide stiffness, damping, wear resistance, and dimensional stability. Material choice determines vibration behavior, long-term accuracy, and manufacturability of the precision guideways. This question focuses on the standard material used for lathe beds in conventional machine tools.
Given Data / Assumptions:
Concept / Approach:
Close-grained cast iron is traditionally used for machine tool beds because it has excellent damping capacity, good machinability, and can be surface-hardened at the guideways. Chilled cast iron refers to locally rapid-cooled surfaces (the “chill”) that produce a hard, wear-resistant skin on the sliding ways, which enhances life and accuracy retention.
Step-by-Step Solution:
Verification / Alternative check:
Textbooks and builder catalogs consistently cite cast iron beds (often with chilled or induction-hardened ways) as standard. Steel beds are uncommon due to poorer damping and higher cost to achieve stability.
Why Other Options Are Wrong:
Common Pitfalls:
Confusing the localized hardening method (chill or induction) with the bulk bed material; overlooking the importance of damping in precision machining.
Final Answer:
chilled cast iron
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