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TED's and Profile Line/Surface Help

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Topcat75

Topcat75

Mechanical
Sep 24, 2024
3
Wonder if you guys can help settle a debate.........

In the attached drawing the designer has used TED's to position the centre of a surface profile. I believe that TED's can only be used to position the centre of a hole (accompanied with a positional tolerance) or be used to position the profile of a line or surface. The way the drawing is currently dimensioned it gives no tolerance to the positioning of the features, or am I reading this incorrectly? To note i'm in England so we are following ISO/BS 8888 drawing standards.

Be interested to hear your thoughts.

 
 https://files.engineering.com/getfile.aspx?folder=1b2dd3ab-5b6c-485b-8745-1c6f8daff66f&file=Screenshot_2024-09-23_091941.jpg
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The problem is not with dimensioning the centers by TEDs but with the profile surface tolerance applied to the centers of recesses. Surface profile can only apply to surfaces, not to theoretical centers. However, TED dimensions to centers are valid to locate the surfaces relative to the datum system.
 
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Yes exactly that, if the TED's had been placed on the edge of the feature then that would work or alternatively another dim from the centre to the edge.
 
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The width and height of the features in the pattern need to be TED-defined (to define the theoretically exact profiles of the features), the centers are implied to be centered to the TED-profiles because, well, they are centers (represented by center lines). So, no edge-to-center TED dims are needed.

But again, the leader from surface profile needs to point to a surface. And there should also be grouping modifiers defined per ISO GPS rules to treat it as a pattern.
 
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I think I understand Burunduk, thanks for your help on this one, much appreciated!
 
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