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Re: [mill_drill] odd thread

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  • Chris Demers
    Jerry, Are you looking for the following:  http://en.wikipedia.org/wiki/Trapezoidal_thread_forms Chris ________________________________ From: Jerry Durand
    Message 1 of 11 , May 15, 2013
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      Jerry,
      Are you looking for the following:

       http://en.wikipedia.org/wiki/Trapezoidal_thread_forms

      Chris



      From: Jerry Durand <jdurand@...>
      To: mill_drill@yahoogroups.com
      Sent: Tuesday, May 14, 2013 8:07 PM
      Subject: [mill_drill] odd thread

      Looking through an old book I have on machinery it shows several
      different threads.  One is trapezoidal, instead of say 60 degrees on
      both faces, one is 90 degrees and the other is 45 degrees.  Any idea
      what this would be for?

      --
      Jerry Durand, Durand Interstellar, Inc.  www.interstellar.com
      tel: +1 408 356-3886, USA toll free: 1 866 356-3886
      Skype:  jerrydurand



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    • Jerry Durand
      Not Acme, right triangle. One face is 90 degrees from horizontal, the other is 45 degrees. ... -- Jerry Durand, Durand Interstellar, Inc.
      Message 2 of 11 , May 15, 2013
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        Not Acme, right triangle.  One face is 90 degrees from horizontal, the other is 45 degrees.

        On 05/15/2013 04:06 AM, Chris Demers wrote:
        Jerry,
        Are you looking for the following:

         http://en.wikipedia.org/wiki/Trapezoidal_thread_forms

        Chris

        -- 
        Jerry Durand, Durand Interstellar, Inc.  www.interstellar.com
        tel: +1 408 356-3886, USA toll free: 1 866 356-3886
        Skype:  jerrydurand 
        
      • Arthur Marks
        As already mentioned, that is called a buttress thread. Here is a smaller example I ve cut... http://tinyurl.com/ayorxna Some collets use such a form for
        Message 3 of 11 , May 15, 2013
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          As already mentioned, that is called a "buttress" thread.  Here is a smaller example I've cut...  http://tinyurl.com/ayorxna  Some collets use such a form for their drawbar threads.  There are subtle different types, though, worth noting.  For example: 45-7 degree, 45-5 degree, 45-0 (as you mention).  You can find them in Machinery's Handbook; they haven't been retired to history.    -Arthur


          On Wed, May 15, 2013 at 1:22 PM, Jerry Durand <jdurand@...> wrote:
          Not Acme, right triangle.  One face is 90 degrees from horizontal, the other is 45 degrees.
        • Jim S.
          This is a buttress thread. One use is on the back end of a Mauser rifle bolt. The entire firing pin/cocking assembly screws into the back of the bolt body on a
          Message 4 of 11 , May 15, 2013
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            This is a buttress thread. One use is on the back end of a Mauser rifle bolt. The entire firing pin/cocking assembly screws into the back of the bolt body on a buttress thread. All the force in this assembly is in one direction, with the load provided by the mainspring. Very strong in one direction, not so much in the other (but not needed).
             
            There are specs for some of these threads in Machinery's Handbook IIRC.
             
            Jim (Just a guy who likes to build stuff)
          • largrin
            I cut a lot of buttress threads before I retired. My first encounter with the design was when I was repairing hydraulic cylinders for Bobcats. Since the tubing
            Message 5 of 11 , May 15, 2013
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              I cut a lot of buttress threads before I retired.
              My first encounter with the design was when I was repairing hydraulic cylinders for Bobcats. Since the tubing is thin walled, using a buttress thread helped to not exert force outward, thereby expanding the thread fit. Also, it was said that the thread stood up better to the constant hammering from the full extension of the cylinder.

              The thread actually has a 45° flank, and a 7° flank that took the load.
              Our company purchased insert tooling to make it more efficient time-wise.

              The thing I had to get in my head was to use opposite ground tool bits for internal and external threads.
              The next odd thing is that like all machinists, I would take small cuts and "sneak up" on a very nice fit. With buttress threads, when you test fit, and it wont go, you take .003" more, and it feels too loose. But it isn't too loose, that is the nature of it.

              Larry in WV


              --- In mill_drill@yahoogroups.com, Jerry Durand <jdurand@...> wrote:
              >
              > Looking through an old book I have on machinery it shows several
              > different threads. One is trapezoidal, instead of say 60 degrees on
              > both faces, one is 90 degrees and the other is 45 degrees. Any idea
              > what this would be for?
              >
              > --
              > Jerry Durand, Durand Interstellar, Inc. www.interstellar.com
              > tel: +1 408 356-3886, USA toll free: 1 866 356-3886
              > Skype: jerrydurand
              >
            • Paul
              This also looks like the type of thread used on PVC/CPVC pipe unions. Paul H.
              Message 6 of 11 , May 17, 2013
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                This also looks like the type of thread used on PVC/CPVC pipe unions.

                Paul H.

                --- In mill_drill@yahoogroups.com, Arthur Marks <arthur.marks@...> wrote:
                >
                > As already mentioned, that is called a "buttress" thread. Here is a
                > smaller example I've cut... http://tinyurl.com/ayorxna Some collets use
                > such a form for their drawbar threads. There are subtle different types,
                > though, worth noting. For example: 45-7 degree, 45-5 degree, 45-0 (as you
                > mention). You can find them in Machinery's Handbook; they haven't been
                > retired to history. -Arthur
                >
                >
                > On Wed, May 15, 2013 at 1:22 PM, Jerry Durand <jdurand@...>wrote:
                > >
                > > Not Acme, right triangle. One face is 90 degrees from horizontal, the
                > > other is 45 degrees.
                > >
                >
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