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  • square threads!

    I remember why I don't like to cut them! I half wat done makeing a screw for an irrigation gate. It's 1 5/8 by 2tpi, 5' long. A couple more hours tomarrow and it should be done!

  • #2
    Ouch! I think I would have gone down to my local farm and ranch supply and ordered a new one for $75. If there's a District Irigation Dept. in your area, they might give you one.

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    • #3
      rbregn:
      Not fun to do. Even with inserts and angle seat shims it is still easier to make it on a cnc Lathe (I love those roller bearing travelling steadies - I could watch it all day!)

      You are a better man than me, Gonga Din.

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      • #4
        Even easier to do on a CNC mill.
        Don't work for acme unless you get a tool ground up but square threads are a doddle.
        See:- http://homepage.ntlworld.com/stevens...e%20thread.jpg

        OK gloat over, not everyone has access to a CNC mill, but even the mighty fall <G>
        I was doing a leadscrew cut for a machine the other day. Guy said it was 1/2" x 10 LH acme. Quick measure up and away we go. Got to the finishing passes and something wrong. Loose at the start and then tightening up. Re check diameters, yup bang on 1/2", recheck pitch, Aaaaahhhhhh measures up at 2.5 mm pitch which is 9.8 TPI
        Oh well, another flat battery in the car park of life.....................

        John S.
        .

        Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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        • #5
          I'm making it for the irrigation district! Got it done, had 5 hrs in the project. Now they changed their mind and said they only needed 3' of threads! but thats better then deciding they needed 6'!

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          • #6
            John
            Between that spline, that leadscrew, and my screw ups we could build a ford! (a pile o'scrap)

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            • #7
              All this talk about CNC lathes and mills makes me wonder what I've been doing wrong.

              I cut square threads by wrapping a string around the OD of the stock, adjusting to set the pitch, spray painting it for a layout. Thereafter its a hacksaw, cold chisel and file job.

              Takes a little time but you can do it agaist a fencepost or a barn door.

              Seriously, I saw a home made 2- 2 Square screw made by hand just as I described. It was used in a flume gate as it happened. There were about 40" of thread hand filed in a piece of Naval brass bar stock maybe 6 ft long. It was a trifle rough here and there but it was a superb piece of hand wrought "machine work". It had been in service since the early '40's when I saw it in 1972 or so.

              The old farmer that made it told me a long sad story of how the Corp of Engineers at the time was gutted of personnel to join the Seabees or whatever in WW II. There was no-one repair the works so he had to make do or lose his Victory spuds and sugar beets.

              A follow rest for cutting long skinny screws is an absolute must. It doesn't have to be an official factory made follow rest. One whipped up from scrap iron and a bushing works very well. The few times I cut square threads I cut them with a narrow tool that left about 0.030" stock in the flanks and finished them with a full width tool.

              Funny. I can spot stuff like that flume gate stem from the road at 50 miles and hour but I still can't keep Barbara's relatives straight. Why is that?

              [This message has been edited by Forrest Addy (edited 04-05-2003).]

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              • #8
                <font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
                All this talk about CNC lathes and mills makes me wonder what I've been doing wrong.

                I cut square threads by wrapping a string around the OD of the stock, adjusting to set the pitch, spray painting it for a layout. Thereafter its a hacksaw, cold chisel and file job.

                </font>
                Forrest,
                You are priviliged indeed.
                Not every one has a spray can or compressor &lt;g&gt;

                As regards remembering about the flume gate but forgetting obout the outlaws this is normal. Just carry on you are in good company.

                John S.

                .

                Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                • #9
                  <font face="Verdana, Arial" size="2">Originally posted by Forrest Addy:
                  All this talk about CNC lathes and mills makes me wonder what I've been doing wrong.

                  I cut square threads by wrapping a string around the OD of the stock, adjusting to set the pitch, spray painting it for a layout. Thereafter its a hacksaw, cold chisel and file job.

                  Takes a little time but you can do it agaist a fencepost or a barn door.
                  </font>
                  An easier way is to wrap 2 square bars of pitch size around a round bar of minor dia. size in a tight spiral wrap. Then braze one of them to the round bar to become the screw, and the other into a bored hole to become the nut.

                  For really large pitches you can even drill tap and bolt on the threads

                  [This message has been edited by yf (edited 04-06-2003).]

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                  • #10
                    Forrest

                    You never know when that ability may save your butt. The more you know how to do yourself the less you have to rely on others mistakes.

                    I salute you, Gonga Din.

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                    • #11
                      I've never had to cut a square thread yet, but I've read somewhere that if you cut a 60 degree thread to the depth of the square thread, and then go back and cut it square, it goes much quicker and easier. Maybe you guys have tried this and can tell me if it is a good short cut.
                      THAT OLD GANG 'O MINE

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                      • #12
                        Ya, it helps a lot

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