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

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  • 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
    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.
    Chilliwack BC, Canada

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    • #3
      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.)
      ----------
      Try to make a living, not a killing. -- Utah Phillips
      Don't believe everything you know. -- Bumper sticker
      Everybody is ignorant, only on different subjects. -- Will Rogers
      There are lots of people who mistake their imagination for their memory. - Josh Billings
      Law of Logical Argument - Anything is possible if you don't know what you are talking about.
      Don't own anything you have to feed or paint. - Hood River Blackie

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      • #4
        It was probably used in the making of the Millenium Falcon in Star Wars to a standard that doesn't exist yet.

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        • #5
          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, 04:16 PM.

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

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            • #7
              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

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              • #8
                Sounds like 25 mm to me..

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                • #9
                  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.
                  Chilliwack BC, Canada

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                  • #10
                    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
                    Location: Long Island, N.Y.

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                    • #11
                      Companies do odd things for all sort of reasons.

                      I bought a set of CNC lathe tooling that threads onto a shank. I needed a 5/8" diameter straight shank. Unfortunately, the manufacturer only offered discounted sets with 3/4 & 1" shanks so I bought the 3/4" shank set. I figured it would be easy to make the needed 5/8" shank.

                      Looking at the 3/4" shank I made the assumption it was threaded 5/8"-24 which is a common extra fine series thread. Wrong, it was 5/8"-25!!!!

                      Pretty obvious they want you to buy their overpriced shanks from them. But the tooling is for CNC lathes so cutting a 25 pitch is a piece of cake, as easy as cutting a 24 pitch.

                      Prior to this incident I had a good feeling about this vendor, not so much anymore.

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                      • #12
                        As long as you got a lathe, you can make Any pitch it, cuts , on Any diameter..
                        Same thing for the nuts.

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                        • #13
                          31/32" comes out to 24.6mm and some change. I guess that could be 25mm with a bit of a tolerance on the OD. 0.4mm is about 16 thousandths of an inch so it would be a stretch, but possible I guess. 30 TPI comes to 0.846mm pitch and that could be 0.85mm within the tolerances of the measurement. This is not a standard metric thread pitch. I have metric transposing gears and an extensive collection of change gears plus three additional compound gears, but the closest I can come to that is 0.84375mm: pretty close, but not exact. I and most people here would be hard pressed to measure or even detect the difference on a thread of less than 25mm (1") length. It (0.85mm) really would be an oddball thread. Perhaps others here can cut it. I would love to know the lead screw pitch and the gear combo they would use.



                          Originally posted by BCRider View Post
                          It did to me as well. But the 30 TPI ended up being 0.84666... mm pitch. And that ain't normal even for an oddball metric thread.
                          Last edited by Paul Alciatore; 05-12-2018, 01:43 AM.
                          Paul A.
                          SE Texas

                          Make it fit.
                          You can't win and there is a penalty for trying!

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                          • #14
                            All these metric proposals are great...but the OP said the die is marked 31/32-30.
                            ----------
                            Try to make a living, not a killing. -- Utah Phillips
                            Don't believe everything you know. -- Bumper sticker
                            Everybody is ignorant, only on different subjects. -- Will Rogers
                            There are lots of people who mistake their imagination for their memory. - Josh Billings
                            Law of Logical Argument - Anything is possible if you don't know what you are talking about.
                            Don't own anything you have to feed or paint. - Hood River Blackie

                            Comment


                            • #15
                              I was told years ago the US Navy deliberatly used odd thread sizes on electrical switch gear so standard steel bolts could not be used in place of the desired copper bolts. I know when the electrical shop was throwing away a drawer of parts, I grabbed several taps and dies, they were oddball sizes 9/32X24, 17/64x32 for example). Not sure of this, but it sounds logical (for the Navy!)

                              Steve

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