Left hand trhread versus right hand thread

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Discussion Overview

The discussion revolves around the advantages and applications of left-hand threads compared to right-hand threads. It explores various contexts in which left-hand threads are utilized, including bicycles, automotive applications, and safety measures in gas fittings.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that left-hand threads may offer advantages in preventing unscrewing in applications involving rotating objects.
  • It is noted that left pedals on bicycles typically use left-hand threads to avoid loosening during use.
  • Historical examples are provided, such as left-hand lug nuts used in some cars and their decreasing prevalence.
  • Left-hand threads are mentioned as a safety measure in distinguishing between gas and oxidizer gas bottles, with specific examples given for fuel gas and oxidizer gas fittings.
  • One participant questions whether gas lines are always fitted with left-hand threads, indicating uncertainty about the universality of this practice.

Areas of Agreement / Disagreement

Participants express various viewpoints on the advantages and applications of left-hand threads, with some agreeing on their usefulness in specific contexts while others raise questions about their general applicability, indicating that the discussion remains unresolved.

Contextual Notes

There are limitations regarding the assumptions made about the prevalence and application of left-hand threads in different contexts, as well as the lack of clarity on whether certain practices are universally applied.

renjith_p
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Does a left hand thread offer any advantages over a right hand thread?
 
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Left pedals on most bicycles have left-hand threads to keep the pedal from unscrewing. Some cars (MGs, e.g.) used to have left-hand lug nuts on the left side, but that's not so common anymore. Some circular saw blades are secured with left-hand nuts for a similar reason.

Turnbuckles obviously have opposite handed threads on either end.

Fuel gas bottles have left hand threads & oxidizer gas bottles have right hand threads as a safety measure for welders. That's why the propane tank on your gas grill is left-handed.
 
obafgkmrns said:
Some cars (MGs, e.g.) used to have left-hand lug nuts on the left side, but that's not so common anymore.

When I was a teenager I nearly stripped the lug nut studs on my Mom's '65 Dodge when changing a flat. The nut seem to be getting tighter and a friend watching suggested it might have a left hand thread, which it did.
 
They prevent unscrewing in applications where the screw fixes a rotating object, and also help to differentiate gas from hydraulic/liquid/etc lines in cars, burners, etc.
 
LJW said:
They prevent unscrewing in applications where the screw fixes a rotating object, and also help to differentiate gas from hydraulic/liquid/etc lines in cars, burners, etc.

Are u saying that gas lines are always fitted with left hand theads?
 

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