berol Posted July 7, 2017 Share Posted July 7, 2017 Have placed my Absolute Datum 00 for both X & Y axis at the lower right hand corner of my rectangular part. Have dimensioned my part using the toolbar ordinate tab. I know from previous experience that some axis positioning is going to be negative when I go to drill these holes with my mill. With the absolute datum at the lower right corner & because of the size of the part it will be in quadrant 2 of the Cartesian plane. Why then don't some dimensions show as negative? Thanks Quote Link to comment Share on other sites More sharing options...
eldon Posted July 8, 2017 Share Posted July 8, 2017 AutoCAD uses the absolute coordinate value of the current UCS to determine the ordinate value. So there will never be a negative value. Quote Link to comment Share on other sites More sharing options...
berol Posted July 8, 2017 Author Share Posted July 8, 2017 Not sure I understand. When I look at a diagram of the Cartesian Plane, quadrant 2, the upper left hand quadrant shows -X and +Y. When I input ordinate dimensions into my digital readout on my mill that move to that quadrant 2, the X needs to be negative & the Y positive. Quote Link to comment Share on other sites More sharing options...
eldon Posted July 8, 2017 Share Posted July 8, 2017 When AutoCAD set up the ordinate dimension system, they seemed to have set up a datum point that was to the left and lower than any features. So they expected all dimensions to be positive and thus took the 'absolute' value of any dimension. I don't think that they considered anyone to be devious enough to go to the left and down from the datum point. You and I know about the various quadrants, but AutoCAD apparently does not for ordinate dimensions. You can always override the text. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.