Any room for improvement on this drawing?

[rollingcloud]

The function of the rod is to provide a platform (datum C) for a spring and a sealing surface (datum B), when pressure is too high, the rod moves to the right.
My main concern is the feasibility of the total runout over short distance. (Datum D is not critical, guided by a bushing to prevent too much misalignment.)

 

[pmarc]

The OP said in his initial post that "when pressure is too high, the rod moves to the right".

So if it can move to the right, the cone is not always the stopper in the axial direction. So in the "too-high-pressure" position, the stopper may be the conical surface on the sleeve sitting over datum feature A and directly contacting the flat face I asked about.

Of the two secondary datum feature candidates, the flat surface simply seems to be easier / more convenient feature to use.

 

[Burunduk]

I see. Good point.

 

[greenimi]

Of the two secondary datum feature candidates, the flat surface simply seems to be easier / more convenient feature to use.

Pmarc,
You said the flat surface simply seems to be easier...., but both candidates are flat: original datum feature B and your proposed flat surface("Couldn't the flat face that is perpendicular to datum feature A and is currently controlled with the parallelism tolerance of .001 to B be used as secondary datum feature for this part")

For me it's six of one, half (a) dozen of the other...

 

[greenimi]

pmarc,
For the part stability (maybe during measurement) do you want the secondary (lets say flat surface B) to be closer or further away from the primary (datum feature A)? I am thinking which one should the OP chose...
What is your experience ?

 

[pmarc]

greenimi,

I was talking about the choice between the flat surface and the cone.

Regarding the stability question, I am not sure I have one rule for that. It is a case-by-case decision.

 

[3DDave]

Just a thought... Couldn't the flat face that is perpendicular to datum feature A and is currently controlled with the parallelism tolerance of .001 to B be used as secondary datum feature for this part? Then the cone and the spring platform could be controlled with profile toleranes wrt A|B.

Neither flat surface ever uniquely locates or orients the part - both are associated with adjustable features. The only axial locator is the cone. The location on the cone is best set by a gauge diameter datum feature target as a base for other axial location controls.

 

[pmarc]

That's of course an option.