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Thread: 31/32", 30 TPI; what manner of wacky thread is this?

  1. #1
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    Default 31/32", 30 TPI; what manner of wacky thread is this?

    Hello,

    I have a die for the aforementioned threadform. It's parallel and looks to be 60 degree profile. The die is 2" OD and 5/16" thick, and is marked 'Millenium', along with size and thread pitch.

    Is this some sort of obsolete, proprietary, or industry-specific thread?

    Thanks.

  2. #2
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    Could it be homemade for some specific task?

    I've done that a time or two. One in particular that I did was to allow the use of a 1/2" clear bore with threaded plugs at each end. I made up a special size that worked out into the walls of the 1/2" existing hole. I don't recall the major diameter but it was a very odd number.

    Even if it was some factory made tap perhaps it was a special related to some product called Millenium or for a company of that name that needed a special size.

  3. #3
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    Quote Originally Posted by Excellent View Post

    Is this some sort of obsolete, proprietary, or industry-specific thread?
    Yes. :-D

    Does this die look "old"?" My impression is that companies didn't get serious about universally standardized threads until around 1900, or later. There were standards prior to that, but there was still a lot of company-based standards that were unique to a specific company. That occurred because 1) when the company first established its standard, there wasn't any other, and they kept making their product based on their thread standards for parts compatibility or 2) they deliberately wanted to be different so customers would have to come back to them for parts.

    If you have ever measured a thread on a Starrett product, you probably found it to be an oddball thread For instance., the screw in Starrett adjustable parallels is 3-52, which totally doesn't exist anywhere else. Victor Machinery Exchange, which sells all manner of weird taps and dies, doesn't have it. (Neither do they have 31/32 - 30, for that matter.)
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  4. #4
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    It was probably used in the making of the Millenium Falcon in Star Wars to a standard that doesn't exist yet.

  5. #5
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    It's probably some thread Harbor Freight uses. I had to buy 3/32-32 and 3/16-24 taps to use with the SHCS pack I bought from there. That is, if I wanted to use those screws. All the rest of the screws in the pack were common sizes.
    Last edited by CCWKen; 05-11-2018 at 03:16 PM.

  6. #6
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    The 3/32-32 would be equal to a #3-32 and 3/16-24 would be equal to #10-24.

  7. #7
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    A special certainly, possibly for a locking nut thread on a 1" shaft, so a bearing race or seal could pass easily over the thread? Just guessing.
    'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

  8. #8
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    Sounds like 25 mm to me..

  9. #9
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    Quote Originally Posted by 754 View Post
    Sounds like 25 mm to me..
    It did to me as well. But the 30 TPI ended up being 0.84 something mm pitch. And that ain't normal even for an oddball metric thread.

  10. #10
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    Quote Originally Posted by 754 View Post
    Sounds like 25 mm to me..
    I think you've confused 31/32 with 63/64.

    31/32 =0.96875
    25mm=0.98425
    63/64 =0.984375

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