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    Hi, Iv read that 0.614*pitch is the recommended thread depth for single point threading.. but is that for 'proper' threadforms or sharply pointed turning tools? What would it be for sharply pointed turning tools if its for proper threadforms?
    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

  • #2
    "Proper" thread form for UN does not use a sharp pointed tool.

    That's where it gets a little sticky...

    "Proper" thread depth is determined by the pitch diameter measurement, not the minor diameter, or depth from major diameter.

    Depth calculations are sometimes handy to get an idea of how deep to cut before you start measuring with wires etc.
    Last edited by Glenn Wegman; 01-21-2010, 07:59 AM.

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    • #3
      Unfortualy I don't feel like grinding a new tool for every TPI range, so a select few tools will have to do, hence im wondering what kinda range there is beween 'ideal' threadform and pointed..
      My tools are not totaly pointed, but likey moreso then the TPI would call for. As less pointed.. doesnt work very well.
      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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      • #4
        This might work for what you want to do.



        Vee-Form tool= sharp V tool

        NF or National Form tool= tool with proper tip truncation.
        Last edited by Glenn Wegman; 01-21-2010, 08:08 AM.

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        • #5
          Originally posted by Glenn Wegman
          This might work for what you want to do.



          Vee-Form tool= sharp V tool

          NF or National Form tool= tool with proper tip truncation.
          Really nice chart. Where did you find this chart?

          Harold
          For those having fought for it, Freedom has a flavor the protected will never know.
          Freedom is only one generation away from extinction.

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          • #6
            Harold,

            I have no idea, it's been in a file folder with some other charts as long as I can remember.......

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            • #7
              The sharp tool will work, the standards folks just realized that the point won't last long so they built in some wear clearance. As Glen mentioned though, proper fit is determined by pitch diameter. Machinery's Handbook has a mess of charts giving the tolerances for major, minor, and pitch diameter for the standard and some not-so-standard threads.
              Stuart de Haro

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              • #8
                Originally posted by hornluv
                The sharp tool will work, the standards folks just realized that the point won't last long so they built in some wear clearance. As Glen mentioned though, proper fit is determined by pitch diameter. Machinery's Handbook has a mess of charts giving the tolerances for major, minor, and pitch diameter for the standard and some not-so-standard threads.
                The standards people realised that a pointed tool gives a smaller core diameter and induces a stress raiser, both of which weaken the threaded item. In many cases this simply doesn't matter because the thread isn't under any great load.
                Paul Compton
                www.morini-mania.co.uk
                http://www.youtube.com/user/EVguru

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                • #9
                  I have the same chart Glenn and I got it from a machinist years ago. I posted it here several times and was getting ready to repost it when I saw you had already done so.

                  I use that chart all the time, it's the first chart I go to when starting to cut a thread. I have found that the Depth of Compound Feed--Single Depth--N.F. Tool column is the most accurate depth to go for. If you cut to about .005" less than the listed number and start using the test nut or measuring with wires the final thread will be close to the number in that column.

                  That chart is the best thing I have found for single point threading. I know I have used it for over 20 years and have found nothing better.

                  Also, I too got tired of putting the designated flat on the end of each threading tool for each size and just use a sharp V now with a light stoning of the sides and tip.
                  It's only ink and paper

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                  • #10
                    For certain, that's a good chart to have and it will become a part of my library.

                    Harold
                    For those having fought for it, Freedom has a flavor the protected will never know.
                    Freedom is only one generation away from extinction.

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                    • #11
                      Originally posted by hwingo
                      Really nice chart. Where did you find this chart?

                      Harold
                      I recognize that, it is from the Atlas / Craftsman Lathe Manual. Notice that this is National Form, iirc this is not the Unified thread series which replaced national form in 1948, the specs are a little different...../video_man
                      Last edited by Video Man; 01-21-2010, 01:21 PM.

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                      • #12
                        Yes, but it's still a 60* V and if used with care it works. Remember, charts are sometimes a guide not an exact truth.
                        It's only ink and paper

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                        • #13
                          The sharp V column would be the same for either.

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                          • #14
                            It's always nice to do stuff by the numbers but the way I was taught was a little more casual: cut untll it looks like a thread then stop and gage or measure. It's worked for me for - um - 244 years now or it seems like it.

                            And Glenn's right. The end of the tool is suppose to have a flat on the tip. There are specific standards of course but you can wing that for non-fussy threads. I use 1/5 to 1/6 pitch for the flat width for external threads and 1/10 to 1/16 for internal. This ensures there wll be no crest/root interferance in the assembled thread. Those little comparator loupes ( http://www.measuringmagnifiers.com/ ) work well even if they are a bit expensive. You put the graticule right on the tool and read the tip width right off the scale. Naturally you have to calculate the depth comp.

                            The flat at the tip of the threading tool will affect the threading depth. The nice three and four digit numbers shown in the charts represents a theoretical calculation. If you cut the threads using the charts data, you have to compensate for the actual tip flat of the tool you are using then adjust the threading depth you cut to. Stop a few thou short of full depth and check/gage. Don't thread right to calculated depth with a fresh tool. You can always take off a little more but so far cutting tool technology hasn't brought us a "puttin'-on" tool.
                            Last edited by Forrest Addy; 01-21-2010, 03:34 PM.

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                            • #15
                              Yes, and that's why I cut short and test to finish size.
                              It's only ink and paper

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