Given this part begins life as a casting, I would say it essentially defines the central axis of this part from that external cast "diameter." The draft angle, as it were, is essentially inconsequential to final form/fit/function. Machined surfaces defined from there-XYZ-(initially), will be manufactured. In essence, using machined surfaces as datums, measuring the resultant (remaining-not completely machined away) cast surfaces to be in specified tolerance. I am curious if customer specifications defined the symbol in the upper half of the Y datum target symbol. Please let me know if you can.
Given this part begins life as a casting, I would say it essentially defines the central axis of this part from that external cast "diameter." The draft angle, as it were, is essentially inconsequential to final form/fit/function. Machined surfaces defined from there-XYZ-(initially), will be manufactured. In essence, using machined surfaces as datums, measuring the resultant (remaining-not completely machined away) cast surfaces to be in specified tolerance. I am curious if customer specifications defined the symbol in the upper half of the Y datum target symbol. Please let me know if you can.
