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Is there a convention to use (0, 0, 0) as the center of a CAD drawing? If so, why? Wouldn't it be easier to use (0, 0, 0) as the bottom left corner and start drawing on the positive coordinates?

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    $\begingroup$ First or third angle? $\endgroup$
    – Solar Mike
    Apr 15 at 5:39
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    $\begingroup$ It depends if the part is symmetric or not. $\endgroup$ Apr 15 at 7:20
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    $\begingroup$ I believe there are some CAD packages where the bottom left corner is the default origin. But having the origin at the center is very beneficial when dealing with symmetric parts as jr swift said, any cylindrical or round shape in particular where your diameter is centered at the origin. $\endgroup$
    – jko
    Apr 15 at 11:32
  • $\begingroup$ A mechanical drawing follows rules whether or not generated using CAD tools. As the comments suggest, location of origin in a drawing should be chosen so as to make the dimensioning as simple and clear as possible to those who will read the drawing. $\endgroup$ Apr 15 at 12:10
  • $\begingroup$ You need to know how to set the global setting for the drawing area. Use the "help" facility in the software and find the topic by keyword search. $\endgroup$
    – r13
    Apr 15 at 18:48
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While there are no conventions for the cad file itself, most folks will look to use the coordinate system datums to their advantage. This involves considering the fit and function of the part.

For example if a block is bolted, consider using the bolt hole rather than the edge. However if the two edges of a block have a bigger impact on how it fits, consider using their connecting corner.

This can also reduce time required to recalculate constrained positions in an assembly when parametric parts are modified. Since the constrained features will not move as much, smaller transformations are performed on the part's coordinates as a whole and it tends to make convergence to meeting constraints easier.

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