Tolerance stacking

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  • Tolerance stacking

    What would be the best way to Explain this to A Boss that hasn't got a clue on GD&T 2.883 +/- .003 O/ .005 I've tried and he is just not getting it. I've thought about a club or rubber hose but this may result in me being a free agent.



    Last edited by why me; 05-04-2009, 08:50 AM.
    sigpicTHE TASK AHEAD OF YOU, IS NEVER AS GREAT AS THE POWER BEHIND YOU. I Fight for Freedom and Pray For Peace..

  • #2
    Its a diameter & roundness it appears........Thats fairly simplistic. If he don't understand that.........sorry no help from me.
    sigpic.....Its called golf because all the other 4 letter words were taken

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    • #3
      Not sure if I can help, but I do have one question: Isn't the circularity tolerance almost always supposed to be less than the diameter requirements? It's supposed to be used to refine the size.
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      • #4
        Dear Mr. Boss...

        The callout of 2.883 is the size tolerance... It can have a diameter between 2.880" and 2.886". The .005" is the FORM tolerance. A diameter can be within specification without being round. The roundness controls the FORM of the part so that it is not allowed to be deformed more than .005".

        Get it now? If not, please find another career...
        Last edited by Mike Johnston; 06-25-2007, 11:57 AM.

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        • #5
          Try showing him this, maybe he'll undrestand cartoons!!
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          If A Pretty Poster And A Cute Saying Are All It Takes To Motivate You,
          You Probably Have A Very Easy Job. The Kind Robots Will Be Doing Soon.

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          • #6
            Originally posted by Sinned View Post
            Not sure if I can help, but I do have one question: Isn't the circularity tolerance almost always supposed to be less than the diameter requirements? It's supposed to be used to refine the size.
            That's what I keep telling him He won't change his drawing. You see I work for engineering here and they seem to hire a few guys that know just enough to make Pro-E work but dont have a grasp on GD&T .
            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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            • #7
              I don't get the problem. Looks like a valid callout to me. The diameter is 2.883±.003 so the diameter can be out of round up to .006 and still fall within tolerance. Lets say one way measures 2.886 and 90º to that measures 2.880 - .006 out of round right? Now, he wants roundness to be better than that. So, he applies |O|.005| to it to control the roundness to .005 or better no matter what the diameter is.

              Am I wrong here?

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              • #8
                You're right. I wasn't thinking .006 for the total tolerance. Sorry, not enough caffine this morning. Plus it's monday!
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                If A Pretty Poster And A Cute Saying Are All It Takes To Motivate You,
                You Probably Have A Very Easy Job. The Kind Robots Will Be Doing Soon.

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                • #9
                  Perfectly valid call.

                  The method of determining size has little to do with the form evaluation. I can imagine a hole with a form of 0.020" that still will calculate back to a size that will fall right into your +/-0.003" call, along the way Goodluck is arguing.



                  Jan.
                  Last edited by Jan d.; 06-25-2007, 02:13 PM.
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                  • #10
                    I understand all of this above but what he doesn’t understand is why on one part the CMM measures the Diameter in and the form of the circle out and the other
                    Both are out. Just like you said if you use all of the tolerance in two directions
                    Your form will be out. the cmm does a best fit on the circle for Diameter.

                    It's the old thing of if the CMM reports good numbers no questions it But you start getting bad reports, Your program is wrong you didn't measure them right. He even went so far as to measure the circle on the manual (using only 4 points) and said see I can get the part in tolerance which you can if you hit the right 4 points but if I’m correct in my thinking you can't accurately measure form using only four points
                    Last edited by why me; 05-04-2009, 08:50 AM.
                    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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                    • #11
                      Originally posted by why me View Post
                      I understand all of this above but what he doesn’t understand is why on one part the CMM measures the Diameter in and the form of the circle out and the other
                      Both are out. Just like you said if you use all of the tolerance in two directions
                      Your form will be out.[ATTACH]1494[/ATTACH] the cmm does a best fit on the circle for Diameter.

                      It's the old thing of if the CMM reports good numbers no questions it But you start getting bad reports, Your program is wrong you didn't measure them right. He even went so far as to measure the circle on the manual (using only 4 points) and said see I can get the part in tolerance which you can if you hit the right 4 points but if I’m correct in my thinking you can't accurately measure form using only four points
                      That would depend on the form you are measuring. AND, he hit it RIGHT ON THE NAIL HEAD, he said, IF YOU HIT THE RIGHT 4 POINTS. That is his solution in a nut shell. Does not matter if it is in or out, if you can, by tweaking your touches, make it APPEAR in, then it is a good part, end of story. Typical bean-counter mentality. Make it appear in so we can get paid for it, makes no difference if it is actually out of tolerance and by being out of tolerance 57 people will die in a horrible plane crash, we already got out money. Peckerhead!

                      If you are measuring a 3mm diameter, yeah, you could probably get away with 4 hits (but even so, 7 to 12 would be better, for form), but if you are measuring 150mm diameter, no-way-in-he11 is 4 hits enough.
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                      Originally posted by AndersI
                      I've got one from September 2006 (bug ticket) which has finally been fixed in 2013.

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                      • #12
                        Originally posted by Matthew D. Hoedeman View Post
                        That would depend on the form you are measuring. AND, he hit it RIGHT ON THE NAIL HEAD, he said, IF YOU HIT THE RIGHT 4 POINTS. That is his solution in a nut shell. Does not matter if it is in or out, if you can, by tweaking your touches, make it APPEAR in, then it is a good part, end of story. Typical bean-counter mentality. Make it appear in so we can get paid for it, makes no difference if it is actually out of tolerance and by being out of tolerance 57 people will die in a horrible plane crash, we already got out money. Peckerhead!

                        If you are measuring a 3mm diameter, yeah, you could probably get away with 4 hits (but even so, 7 to 12 would be better, for form), but if you are measuring 150mm diameter, no-way-in-he11 is 4 hits enough.
                        I'm measuring 73.23mm that's a whole other story my print is in Inches & my Cad model I have to report to the Customer in MM and to My Dino Engineer in inches so he can under stand it.
                        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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