Creating New Datums
There are three kinds of Datums that you can create within an alignment document. Each type has unique benefits and limitations. Three Point Datums are very quick and simple to create, but they are not as readily reproducible as the other types and it is difficult to establish a specific, reproducible origin on the part. Three Sphere Datums are more reproducible than Three Point Datums, but also have limitations for setting an on-part origin. Custom Datums provide the greatest flexibility for creating Datums and are the most reproducible because you use specific part geometry to create the alignment. The creation of Custom Datums is more involved that the other types.
Datums may be created from attributes of the part itself or a jig that secures the part for work. If you use features of the jig to establish the Datum you must make sure that the relationship between the jig and part does not change when you move the part or digitizer to gain access to other sides of the part. If the relationship between the elements used to create a Datum and the part change you cannot reuse the same elements to re-establish a Datum.
Datums align your part to specific SOLIDWORKS views. To learn how to set the view you wish to align to, read this topic:
To better familiarize yourself with the creation of specific Datum types, read the following topics: