Is there a way to force the ordinate dimension to show plus or minus deviation from the established zero datum? Attached pic shows example what I'd like (red values illustrated).
Until you specifically establish the X-Y axes on the drawing, I don't believe there are "positive" or "negative" dimension values because there is no establish reference to dictate plus or minus.
Left reading/bottom reading drawings don't imply this.
Without reference axes (a coordinate system reference), all dims are just values that are left/right or up/down of their dimension origins.
Ordinate dim values, like all other dim types, are simply the distance from the chosen dimension origin (it's not a datum, at least not in the image--I know, splitting GD&T hairs) along the ordinate dim entity's alignment vector.
Not that there can't be negative dimension values on drawings. I believe the Hole Table feature can have negative dims, but it establishes an X-Y reference.
Ordinate dims don't have this coord system reference capability,
I'm assuming your drawing doesn't indicate reference axes, but i'm not recommending adding the X-Y reference.
By doing so, you're adding fabrication process instructions, which technically, aren't supposed to be on drawings.
Even without the X-Y reference, specifying negative values adds fab instructions.
Lastly, I try not to hard-code anything, if at all possible, because sooner or later, I'll get bitten.
So, per the above blather, I'm recommending that you don't +/- ordinate dims (outboard of tolerances).
Just my tuppence.
Oops, I should have also mentioned, these circles are sketched on the drawings. They are not hole features in a part.
Not by default. The usual manual workaround is to add the - sign to a dimension, then create and save a dimension Style and apply that to other dimensions.
2014 SOLIDWORKS Help - Style
Another way is to pre-select all the target dimensions and add the - sign en masse.
Thanks folks. I was obviously recollecting hole table dimensioning capability, which doesn't apply to this problem for the reasons you have kindly elaborated on.
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