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Why do US lamp parts use an "IP" thread ?

  1. Jul 7, 2016 #1

    Stephen Tashi

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    Science Advisor

    Is there a reason (other than tradition) why lamps in the USA use threaded tubing that has an "IP" thread standard ?

    Does Europe have a better approach ?

    I find it irritating that the nuts and connectors in the main part of local hardware stores don't fit the threaded tubing in lamps. You have to shop in the "lamp parts" section of the store and the nuts and connectors there are (to me) inconveniently small and delicate.
  2. jcsd
  3. Jul 7, 2016 #2


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    Gold Member

    My belief is that this, like many such things, was done for a very simple reason. Money. If the manufacturers used standard parts, you could buy them from just anyone. This way you have to buy purpose-made parts and they make a bit of money on it. That's probably no longer true in that there are likely now many sources for such parts, but that's my belief about why it started that way.
  4. Jul 8, 2016 #3
    The threads are straight pipe threads. Most pipe threads you encounter (like in plumbing) are tapered. I read somewhere that electric lamps use the straight threads (and the pitches) originally used in the gas pipes in the gas lamp days. Presumably that made the customer's lives easier in 1910 or thereabouts.
  5. Jul 10, 2016 #4


    Staff: Mentor

    "Historical accident" is the common answer to many such questions. And it is a very good reason. Consider the benefits of changing such a standard compared to the costs. Only rarely do the benefits outweigh the costs.

    My pet peeve is the arbitrary choice that Benjamin Franklin made about which polarity of electric charge was called "positive". I wager that one million years from now, physicists will still be using Franklin's convention.
  6. Jul 10, 2016 #5


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    And cussing all the while.
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