Recently, one of my company's products has a new drawing updated, a dimension related to positional tolerance using common Datum, but I don't know much about common datum, I have searched many documents but Haven't gained much knowledge, looking forward to guidance, specifically in the case like in the photo, what does "B-C" mean?
This callout can only be used if the datums share an axis. This callout is usually used for parts turned in a lathe that will end up spinning on these datums when they're being used in the field.
That's not quite true. Datums that share a common axis are just one of the possible types of common datum. You can also have offset parallel planes. If you're working to ISO, a common datum can be any pattern of features - such as bolt hole patterns or multiple width features. We recently considerably expanded our support for different types of common datum - see here:
PC-DMIS Help Center - 2023.2 (hexagonmi.com)
This callout can only be used if the datums share an axis. This callout is usually used for parts turned in a lathe that will end up spinning on these datums when they're being used in the field.
That's not quite true. Datums that share a common axis are just one of the possible types of common datum. You can also have offset parallel planes. If you're working to ISO, a common datum can be any pattern of features - such as bolt hole patterns or multiple width features. We recently considerably expanded our support for different types of common datum - see here:
PC-DMIS Help Center - 2023.2 (hexagonmi.com)
