Help dimensioning this feature: Profile of a Surface to Datums

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  • Help dimensioning this feature: Profile of a Surface to Datums

    This is a surface on the left side of an engine block. I dont think I have ever encountered this. D and E are dowel holes on the front face...should I construct a line between the 2 dowels, call it D-E and dimension to that? Its a surface so, measure a plane, and dimension its profile back to A and D-E.....?

    Im guessing this profile controls the location of the surface because there is no definitive area that says where this surface should be.

    gdt.jpg
    Last edited by Mike_B; 11-26-2013, 08:53 AM.
    Browne & Sharpe Global Advantage 12|22|10
    PCD 2012 MR1 CAD++

  • #2
    That is my guess not looking at the drawing. When a profile is called back to a datum it is usually form and location. Im guessing they want the surface control to the datum a plane and also controlled by the datum D-E line. How do they know where to machine or make the surface if there is no dimension where it should be? I imagine there has to be a dimension of some sort with it called back to datums
    sigpicSTANDING CORRECTED IS THE ONLY WAY I STAND

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    • #3
      Originally posted by Mike_B View Post
      This is a surface on the left side of an engine block. I dont think I have ever encountered this. D and E are dowel holes on the front face...should I construct a line between the 2 dowels, call it D-E and dimension to that? Its a surface so, measure a plane, and dimension its profile back to A and D-E.....?

      Im guessing this profile controls the location of the surface because there is no definitive area that says where this surface should be.

      [ATTACH=CONFIG]8731[/ATTACH]
      Mike you are correct in thinking that you need to construct a line between these two holes "D" and "E" and then call that line Datum "D - E", it will be your secondary datum and "A" will be your primary datum. Datum "D-E" is commonly refered to a "dual feature datum". You should be able to google it and find out a little more information about the datum callout.
      If there wasn't a wrong way, I would have no way at all.

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      • #4
        Thank ya sir..
        Browne & Sharpe Global Advantage 12|22|10
        PCD 2012 MR1 CAD++

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        • #5
          And the front face is datum -A- I presume?
          sigpicSummer Time. Gotta Love it!

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          • #6
            Centerline of crank..running parallel with this face
            Browne & Sharpe Global Advantage 12|22|10
            PCD 2012 MR1 CAD++

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            • #7
              Originally posted by Mike_B View Post
              This is a surface on the left side of an engine block. I dont think I have ever encountered this. D and E are dowel holes on the front face...should I construct a line between the 2 dowels, call it D-E and dimension to that? Its a surface so, measure a plane, and dimension its profile back to A and D-E.....?

              Im guessing this profile controls the location of the surface because there is no definitive area that says where this surface should be.

              [ATTACH=CONFIG]8731[/ATTACH]
              Hi Mike,
              You may want to step up your self-education (or convince your employer to assist with this) and get ahold of some Geometric Dimensioning and Tolerancing training materials.

              We actually offer a class called Applied GD&T for PC-DMIS that is a whopper: it not only teaches you GD&T (as defined by the ASME Y14.5 standard) quite correctly but also teaches you how to use PC-DMIS to check the stuff.

              More and more industries are moving to GD&T for blueprints. You're in automotive where it's completely standard.
              It's become pretty much a required skill that to run a CMM you have to know GD&T, and not just know of it but know it well enough to explain it to people.

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