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Home / Software / Help Index / Specifications / Datums


Datums, described in more detail here, are locations on a part that indicate a "base" from which measurements are taken. You can specify datums for your design but are not required to do so.

To specify datums:
  1. Draw a straight line.
  2. Apply menu Line | Machine | Datum
  3. Use Comments To Machinist text to label each datum (usually A, B, C).
  4. Generally, 2D parts have 2 datums and 3D parts have 3.
    If no datum is specified, eMachineShop will apply a reasonable datum such as the lower and left edges of a rectangular part or the center of a circular part.