Function of the half-nut on a lathe Evaluate the statement: “Half nut is used to lock the lathe carriage to the lead screw for thread cutting.”

Difficulty: Easy

Correct Answer: True

Explanation:


Introduction / Context:
Accurate thread cutting on a lathe requires synchronizing carriage motion with spindle rotation via the lead screw. The half-nut mechanism is central to engaging and disengaging this drive precisely.



Given Data / Assumptions:

  • Engine/centre lathe with lead screw and feed rod.
  • Half-nuts mounted in the apron clamp around the lead screw.


Concept / Approach:
When the operator closes the half-nuts, the carriage couples directly to the lead screw’s helix, converting screw rotation into precise linear travel for thread cutting. Disengaging the half-nuts disconnects the carriage from the lead screw to stop or retract.



Step-by-Step Solution:
Identify purpose: synchronize carriage feed with spindle via gear train and lead screw.Engage half-nuts: secure carriage to lead screw for the threading pass.Therefore, the statement is true.



Verification / Alternative check:
Lathe apron diagrams show separate clutches for power feeds (via feed rod) versus half-nuts for threading (via lead screw).



Why Other Options Are Wrong:
(B) and (E) contradict standard lathe design; (C) and (D) add unnecessary conditions—thread type and speed do not change the core function of half-nuts.



Common Pitfalls:
Confusing feed-rod driven power feed with lead-screw threading; opening half-nuts mid-pass causing pitch errors; mis-timing re-engagement on metric threads when using an imperial lead screw.



Final Answer:
True

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