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  • Measuring method: perpendicular and length tolerance

    Discussion in 'The main mechanical design forum' started by siem, Jun 28, 2011.

    1. siem

      siem Member

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      Hi Guys,


      I'm in a discussion with my colleagues over the way something must be measured. I'm drawing a part which has a length and perpendicular tolerance as shown in the drawing specification. I believe that the perpendicular tolerance does not influence the total length of the part, due to the fact that the length of part must be measured over the complete height of the part. As shown in measuring methode 2.


      One of my colleagues thinks that the length is only measured on the side on which the dimension is located.


      Which of the measuring method's is correct? Please refer to a standard (prefably an European-standard, such as NEN).


      Thanks in advance!


      Siem
       
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    3. siem

      siem Member

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    4. KevinC

      KevinC Well-Known Member

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      I can't view the document.

      But when you design, don't you always measure against the complete height? And you have to also think of the worst case scenario for the parts (regarding to tolerance) when it is fitting into another part.
       
    5. siem

      siem Member

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      Why can't you view the document? It is supposed to me shared with everyone through google doc's.

      My questions lies in the fact IF you measure against the complete height. If you measure against the complete height, the perpendicularity is already "inside" the length tolerance. If you only measure the one edge, the perpendicularity must be added to the total length tolerance. Making the worst case scenario worst.

      Example: (dims are in mm)
      length = 80
      length tolerance= +0.05 / - 0
      perpendicularity tolerance= 0.03

      If you measure against the complete heigth, the maximum total length can be 80.05 mm. Therefore the max perpendicularity per side can only be 0.05/2= 0.025 mm

      If you do not measure against the complete heigth, the maximum total length is 80.05+0.03 = 80.08 mm.
       
    6. siem

      siem Member

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    7. Plamen

      Plamen Member

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      You are absolutely right!

      If both sides are to be considered separately then there should be given both dimensions.

      And because use anticipate a parallelogram of some kind it is for both sides.

      So it is Measuring option 2.
       
    8. jojoaguillon

      jojoaguillon New Member

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      THE MAIN purpose of tolerance is that interchangeability of ones product... perpendicularity tol. doesn't compromise with the length required.it means that if length is 100mm then it must be 100,but it must be closer to 90° relative to the parts indicated in the Datum......
       

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