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  • It's Monday

    I'm dealing with a project engineer a program manager and a GD&T expert!
    They tell me I'm tolerancing true position all wrong. I have a diametric true position hole locating Y,Z with 1mm tol. So I true position the hole with Y and Z and 1mm in the TP.
    First they tell me I have to show X in TP, (ok if you want to see you got it). Next they tell me That the the tolerance on this diametric hole is +/- .5 in all axis. And do it htis way from now on.
    It's Monday with a long weekend is coming.......................
    thanks for the vent

  • #2
    Posta jpg or other forum friendly picture of your print area in question describing your datum structure. Something smells in Denmark.
    sigpic

    James Mannes

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    • #3
      Is the diameter symbol inside the feature control frame?
      Could you post a pic of the FCF in quesion?

      Technically, yes - it is 0.5mm in all directions - but RADIALLY. You cannot simply offer the conventional tolerancing mehtod. that would take away the benefit of using GD&T (Round hole, round pin, round tolerance - not square)
      kb
      RFS Means Really Fussy Stuff

      When all you have is a hammer - everything looks like a nail....
      sigpic

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      • #4
        +-.5 in all axis?????

        NO

        the total deviation can be a maximum of.5mm in any direction,
        so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
        TP is a CIRCULAR tolerance zone, not SQUARE.

        your GDT guy don't know pooh
        bob
        Which one gets ridden today? MPH vs MPG..tough choice, both are FUN
        sigpic

        Starrett RGDC 4028-24 :alien:
        Demon vintages 3.7, 4.1, 4.2, 4.3, 2009

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        • #5
          If the FCF has the diametrical symbol in front of the 1mm tolerance, ask your GD&T expert what he's been smoking this morning. Only if the diametrical symbol IS NOT in front of the 1mm tolerance would you be allowed to have +/-0.5mm.
          Xcel & MicroVal Pfx & Global 37mr4 thru 2012mr1sp3
          Contura Calypso 5.4

          Lord, keep Your arm around my shoulder and Your hand over my mouth. Amen.

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          • #6
            Originally posted by bob mappes View Post
            +-.5 in all axis?????

            NO

            the total deviation can be a maximum of.5mm in any direction,
            so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
            TP is a CIRCULAR tolerance zone, not SQUARE.

            your GDT guy don't know pooh
            bob
            And if you want the cartesian tolerance for a 1mm TP it is .3536
            sigpic

            James Mannes

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            • #7
              I've found a good way to win these type of arguments is to draw a picture. Make it 2d so it is easier to understand. Draw a point. Tell them this point is the nominal location described by the basic dimensions. Now draw them a circle around the point and centered on the point that has a diameter of 1mm. Tell them that is the tolerance zone described by the FCF - assuming
              the fcf is |TP|Ø1.0|A|... Now and here is the good part... Start making theorhetical examples. put an x and y axis on the drawing. Give them a theorhetical point that is +.5 in x and +0 in y. That part is good right. Next give them a theorhetical point that is +0 in x and +.5 in y. That part is also good. Now kick them in the butt and draw a point that is +.5 in x AND +.5 in y. That point should very clearly fall outside of your circle.

              ±.5 in all directions is not the same thing!!!

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              • #8
                this is section cut / basicaly frt a view.
                Attached Files

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                • #9
                  Originally posted by bob mappes View Post
                  +-.5 in all axis?????

                  NO

                  the total deviation can be a maximum of.5mm in any direction,
                  so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
                  TP is a CIRCULAR tolerance zone, not SQUARE.

                  your GDT guy don't know pooh
                  bob
                  I SECOND THIS. DO WE HAVE A THIRD FOR THE MOTION TO CARRY!
                  sigpicTHE TASK AHEAD OF YOU, IS NEVER AS GREAT AS THE POWER BEHIND YOU. I Fight for Freedom and Pray For Peace..

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                  • #10
                    The True position Formula ANSI Y14.5M Pg. 81

                    Here, let them check this out:

                    The True position Formula ANSI Y14.5M Chapter 5

                    The true position formula, and a calculator in a spreadsheet. If you can't tell them they are cave men, call me & I will.

                    Gabriel Ortiz
                    (949) 863-0560
                    Attached Files
                    Last edited by Cumofo; 07-12-2007, 07:51 PM.
                    sigpic

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                    • #11
                      Originally posted by Randy P View Post
                      I'm dealing with a project engineer a program manager and a GD&T expert!
                      They tell me I'm tolerancing true position all wrong. I have a diametric true position hole locating Y,Z with 1mm tol. So I true position the hole with Y and Z and 1mm in the TP.
                      First they tell me I have to show X in TP, (ok if you want to see you got it). Next they tell me That the the tolerance on this diametric hole is +/- .5 in all axis. And do it htis way from now on.
                      It's Monday with a long weekend is coming.......................
                      thanks for the vent
                      The first two OK this really is not their field. But if you got an "expert" telling you this, you are doomed!!!

                      Comment


                      • #12
                        An EXPERT thats never ever wrong and he'll tel ya so.

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                        • #13
                          Originally posted by Goodluck View Post
                          I've found a good way to win these type of arguments is to draw a picture. Make it 2d so it is easier to understand. Draw a point. Tell them this point is the nominal location described by the basic dimensions. Now draw them a circle around the point and centered on the point that has a diameter of 1mm. Tell them that is the tolerance zone described by the FCF - assuming
                          the fcf is |TP|Ø1.0|A|... Now and here is the good part... Start making theorhetical examples. put an x and y axis on the drawing. Give them a theorhetical point that is +.5 in x and +0 in y. That part is good right. Next give them a theorhetical point that is +0 in x and +.5 in y. That part is also good. Now kick them in the butt and draw a point that is +.5 in x AND +.5 in y. That point should very clearly fall outside of your circle.

                          ±.5 in all directions is not the same thing!!!
                          Very good way to explane it Goodluck

                          Originally posted by why me View Post
                          I SECOND THIS. DO WE HAVE A THIRD FOR THE MOTION TO CARRY!
                          I third this for the motion to carry
                          sigpicRegards,
                          Donald Henger
                          B&S Micro Excel Pfx
                          3.5mr2 & 3.7mr3
                          PHH10MQ, TP20 & TP2
                          Country Rocks,But Bluegrass RULES!!!

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                          • #14
                            Well......he's wrong!
                            RFS Means Really Fussy Stuff

                            When all you have is a hammer - everything looks like a nail....
                            sigpic

                            Comment


                            • #15
                              Originally posted by bob mappes View Post
                              +-.5 in all axis?????

                              NO

                              the total deviation can be a maximum of.5mm in any direction,
                              so an extreme example would be .5mm deviation in Y and ZERO deviation in Z....you can't have +-.5 in BOTH directions at the same time.
                              TP is a CIRCULAR tolerance zone, not SQUARE.

                              your GDT guy don't know pooh
                              bob

                              I really have nothing new to add. The answer is pretty straight forward.
                              I just had to comment on the harsh lauguage being used..............
                              sigpic.....Its called golf because all the other 4 letter words were taken

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