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?
When you read the feature control frame out loud you'd say "-B- thru -C-". 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. To measure:
-Construct circles at multiple levels on -B-
-Construct midpoints at each circular level of -B-
-Construct circles at multiple levels on -C-
-Construct midpoints at each circular level of -C-
-Construct a 3D line thru all of the midpoints & you have your "B-C Axis"
When you read the feature control frame out loud you'd say "-B- thru -C-". 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. To measure:
-Construct circles at multiple levels on -B-
-Construct midpoints at each circular level of -B-
-Construct circles at multiple levels on -C-
-Construct midpoints at each circular level of -C-
-Construct a 3D line thru all of the midpoints & you have your "B-C Axis"
