【转帖】datum in a second view

yang686526

datum in a second view
the question i have is if a datum is identified in one view as the centerline of a "feature of size", how might i identify that centerline in another view?  in the second view the centerline is the starting point for a half dimension and the datum feature is not visible.
yes, i realize that gd&t would use possibly a profile callout or a tp callout instead of the half dimension. my problem is that i do not have the influence to mandate a chamge to gd&t.  i would like to start by properly identifying datums. currently, a datum symbol may be attached to a centerline that has 5 coincidental features and there is no way to know which feature truly is the datum.  
i would put the conventional datum symbol in line with the fos dimension line in the first view but what do you do in the second view?
thanks in advance  
does your drawing state in accordance with a.s.m.e. y14.5?
are you familiar with y14.5?
a datum identifier cannot be applied to a centerline.  it must be associated with the fos.
no, it does not state asme y14.5  
i am afraid that i used to be and now i am out of date with the current standard.
in the older revisions the datum "flag" could be attached to a centerline, identifying a centerline that may have been described by tooling points in another view.  would this practice still be acceptable?
thanks,
vegabond
you can identify a centerline as a datum axis in another view.  it is against the standard to identify a centerline as a datum without adding "axis" or "centerline" to the callout.
thanks for the reply, it is not clear to me what you mean by: adding axis or centerline to the callout.  if the datum symbol is in line with the "feature of size" dimension, ref fig 3-4 pg 43 yi4.5, we already know that the center is the datum in the first view.  are you talking about the callout in the second view?
yes, i was refering to any subsequent callouts of that datum.
it would seem that to properly address your problem one would need to know the drawing standard being applied.
vegabond,
if the datum feature is a feature of size, the datum feature symbol is attached to or associated with the size dimension.  by attaching or associating the datum feature symbol with a particular size dimension, it defines a specific point, axis or median plane that is derived from that feature as the datum.
best regards,
heckler
sr. mechanical engineer
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