True Position call-out

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  • True Position call-out

    I've got this call-out

    tp to a.jpg

    on a hole that goes thru the wall of a cast part that is about 1mm thick. I would normaly check this at two depths and report one to the other. But I don't really have enough depth here to make this meaningful. Would it be accurate to recall my iterateive alignment then level to -A- and report it to CAD?

  • #2
    If -A- is a surface they are looking for perpendicularity.
    sigpic.....Its called golf because all the other 4 letter words were taken

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    • #3
      Originally posted by Tested View Post
      I've got this call-out

      [ATTACH]1317[/ATTACH]

      on a hole that goes thru the wall of a cast part that is about 1mm thick. I would normaly check this at two depths and report one to the other. But I don't really have enough depth here to make this meaningful. Would it be accurate to recall my iterateive alignment then level to -A- and report it to CAD?
      I've seen this a few times on stampings for one customer. I talked to their CMM programmer on how they check it. They take 3 sample hits around the hole then however many in the hole. If the hole is not in the leveling plane I create an alignment leveled to the plane the hole is in before reporting the GD&T. With this method I see some deviation but I've never had a hole in a stamping fail this callout.

      This may or may not be the correct way. Some of the GD&T experts will chime in.
      Perry
      B&S Mistral
      3.207 Beta on XP

      Older'n dirt

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      • #4
        Common error from the design team. If it is perp, the symbol should be perp. Seeing the actual drawing (of course) would shed a little light (application). The reason the FCF would be invalid - a tolerance of position MUST be located by basic dimensions. Yes, the tolerance zone does extend the length of the feature - but it is not a valid FCF to simply define a tolerance of orientation (i.e. perp, par, ang) with a tolerance of location (i.e. pos,sym,con).
        kb
        RFS Means Really Fussy Stuff

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

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        • #5
          Originally posted by kbotta View Post
          Common error from the design team. If it is perp, the symbol should be perp. Seeing the actual drawing (of course) would shed a little light (application). The reason the FCF would be invalid - a tolerance of position MUST be located by basic dimensions. Yes, the tolerance zone does extend the length of the feature - but it is not a valid FCF to simply define a tolerance of orientation (i.e. perp, par, ang) with a tolerance of location (i.e. pos,sym,con).
          kb
          I agree. I usually tell the engineer to change the print or i'll report perp. for TP of the diameters................
          sigpic.....Its called golf because all the other 4 letter words were taken

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          • #6
            Originally posted by bw_bob View Post
            I agree. I usually tell the engineer to change the print or i'll report perp. for TP of the diameters................
            TP to -A- is a real callout. It's defined in the book.

            But what I'm asking here is; I can only check the hole at one height, be TP, or PERP. I can't check it at 2 heights. is it ok to setup as I decribed above?

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            • #7
              Not easy to program but a pin gage will give you enough surface area to establish the centerline, that along with the thickness (1mm) will give you a perp value. I agree it would be clearer if perp was the symbol but in effect the position symbol controls that as well.

              .02

              TK
              sigpicHave a homebrew

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              • #8
                Originally posted by Tested View Post
                TP to -A- is a real callout. It's defined in the book.

                But what I'm asking here is; I can only check the hole at one height, be TP, or PERP. I can't check it at 2 heights. is it ok to setup as I decribed above?
                I dont know how the interative alignement would have anything to do with it nor checking it to cad. If you cant measure it per the print then ask the engineer or whoever the customer is "How do you want it checked", otherwise move on.
                Links to my utilities for PCDMIS

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                • #9
                  Originally posted by cmmguy View Post
                  I dont know how the interative alignement would have anything to do with it nor checking it to cad. If you cant measure it per the print then ask the engineer or whoever the customer is "How do you want it checked", otherwise move on.
                  I am, I'm just waiting for Japan to get back with me. Was hopping to have a answer from here so I didn't need to miss PPAP due date.

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                  • #10
                    Originally posted by Tested View Post
                    TP to -A- is a real callout. It's defined in the book.

                    But what I'm asking here is; I can only check the hole at one height, be TP, or PERP. I can't check it at 2 heights. is it ok to setup as I decribed above?

                    Where? what pg and para please. (ASME 14.5M-1994)
                    RFS Means Really Fussy Stuff

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

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