Unknown dimensioning symbol
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  1. #1
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    Default Unknown dimensioning symbol

    Can anyone tell me what these 2 circles with an upside down 7 mean?
    symbol.jpg

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    It sort of looks like it could be Datum hole Centre Line?
    But...

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    That is kind of what I was thinking but can't find any information.

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    Sure looks like "Centerline" mark to me, slightly artistic on the drafters part, maybe even
    "patent drawing" style.

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    Ok thank you for your help

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    The center line of that dowel hole is your X0Y0 Datum, and that hole is 15mm from the dowel, not the end of the part.

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    So, it's just a fancy way to call out the datum... Thank you to everyone for their help.

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    Quote Originally Posted by GRMICHMUSH View Post
    So, it's just a fancy way to call out the datum... Thank you to everyone for their help.
    Not necessarily. You'll often see callouts like this on weldments too.

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    Quote Originally Posted by Mtndew View Post
    Not necessarily. You'll often see callouts like this on weldments too.
    With that symbol?

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    Quote Originally Posted by barbter View Post
    With that symbol?
    I was referring to the "start" notes. Meaning the datum is shifted and not the edges of the part.
    Another place I've seen them a lot is on linear gear racks where the "start" is on a certain tooth or tooth space.

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    What drafting standard is this from???

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    Why not ask the customer/engineer/designer to make sure everyone is in agreement?

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    Back in the (old) world of drawing on a board with pencils and Rotring pens, I used this symbol on the end of every centreline.
    Not exactly the same - I'd write a 'C' with a diagonal 'L' through the middle of the C - so pretty similar.
    It's just the way I was taught.

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    Quote Originally Posted by Peter Neill View Post
    Back in the (old) world of drawing on a board with pencils and Rotring pens, I used this symbol on the end of every centreline.
    Not exactly the same - I'd write a 'C' with a diagonal 'L' through the middle of the C - so pretty similar.
    It's just the way I was taught.
    +1
    But as you said, that was a C


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