Cylindrical feature, datum symbol placement, in line vs not in line with dimension arrow 2

[tN.gineer]

Greetings Forum, I have a simple question about the placement of a datum symbol for a cylindrical feature: Is there any difference in the datum defined by Datum Feature B as indicated in the two figures below? Is either acceptable or only fig. 1?

I know that if the 1.894 dimension was the distance between two planar surfaces instead of a cylinder diameter, then these mean very different things, but what about for a cylinder?

Thanks!

 

[3DDave]

The right hand side is what is used to identify a plane that is tangent to the cylinder.
The left hand side is what is used to identify the axis of the cylinder.

In two planar surfaces, one identifies one face and the other identifies a plane in the center.

 

[Burunduk]

Here are the relevant definitions from ASME Y14.5-2018:

" (d) placed on the dimension line or an extension of the dimension line of a feature of size when the datum is an axis or center plane. If there is insufficient space for the two arrows, one arrow may be replaced by the datum feature triangle. See Figure 6-4, illustrations (a) through (c), (f), and (h); Figure 7-40; and Figure 7-42, illutrations (c) and (d).

(e) placed on the outline of a cylindrical feature surface or an extension line of the feature outline, separated from the size dimension, when the datum is an axis. For curved features, the triangle may be tangent to the feature. See Figure 6-4, illustrations (e) and (g). "

Taken from
6.3.2.1 Datum Feature Symbol Application in Orthographic Views.

In your figure the left side is (d) and the right side essentially conforms to (e), although applied in a different way than the standard's example figures show (they show it on the circular outline of a side view of a cylindrical feature).

 

[3DDave]

I was concerned but clearly the standard does not imply an axis with the right hand side example.

The right side clearly doesn't conform to (e).

 

[Burunduk]

I was concerned but clearly the standard does not imply an axis with the right hand side example.

The right side clearly doesn't conform to (e).

What else is the right side, if not " placed on the outline of a cylindrical feature surface or an extension line of the feature outline " ?