Machine tool construction: The bed of a conventional engine lathe is typically made from which material?

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:

  • Conventional cast construction with ribbed sections.
  • Need for good damping and wear resistance at the guideways.
  • Mass production feasibility and cost considerations.


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:

Identify requirements → stiffness + damping + wear-resistant guideways.Match to material → cast iron with chilled (hardened) way surfaces.Select answer → chilled cast iron.


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:

  • Mild/alloy steels: stiff but poor damping; expensive to stabilize; not typical for beds.
  • Pig iron: a generic term; not the finished engineering material for precision beds.
  • Aluminium bronze: unsuitable for large beds; too expensive and insufficient stiffness.


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

More Questions from Production Engineering

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion