In this Question Line video, Jason answers the following question regarding datums for castings: 

I am trying to understand what the purpose of this generous position tolerance back to a cast datum is for. The cast holes are used for machining set up.

 

Jason discusses the submitted drawing below, as well as presenting another example that he uses to talk about how datum targets, datum reference frames, and multiple datum structures can be of assistance in casting drawings.  

datums for castings fig1

 



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