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I know that there are screws with these features and know how to distinguish them. Usually there are screws on the right thread.

When and what type of screws should I use?

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  • 1
    Generally speaking, every screw you will encounter or should use in a "household" context will be RH threaded. I've only used LH screws in automotive/bicycle/industrial machinery type situations. – whatsisname Nov 6 '13 at 17:32
  • Perhaps you could describe the application for which you would consider a LH thread? – Chris Cudmore Nov 6 '13 at 18:54
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Differences:

  • Righty Tighty, Lefty loosey doesn't work with left-handed screws.
  • Right-handed screws move away from you if you rotate them in a clockwise direction, whereas left-handed screws move towards you.

When to Use Left-Handed Screws

When fretting induced precession would cause the right-handed nut/screw to loosen, a left handed nut/screw should be used.

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  • Chew tawkin 'bout rotational loosing, bub? – HerrBag Nov 6 '13 at 17:38
  • Chrysler products used LH lug nuts for years, but only on the left side of the vehicle – HerrBag Nov 6 '13 at 17:48
  • I read of a large transit system (NYC?) that had LHT sockets and light-bulbs to deter bulb theft. They were a huge customer, and it only needed a production line change in the pressed metal in the socket and bulb base. – DJohnM Nov 6 '13 at 19:00
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    I've found that sometimes the right hand (on the wrench) doesn't know what the left hand (thread) is doing. – mac Nov 7 '13 at 14:21
  • @HerrBag - It was all fun and games sitting back snickering with my buddy at one of our less informed friends trying to remove a flat until he put a swede on it and managed to twist the stud off. Dodge'm – Fiasco Labs Feb 20 '16 at 3:26
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Most common use is probably on a turn buckle. Think screen door sagging fix.

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you can easily distinguish right hand and left hand thread by visualize it.and it is depend on your need that what type of screw you can use for which purpose.

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