Datums Features Symmetrical part

[nry67]

Hi,

I have a question regarding the Datums Features of a fully symmetrical part.

I would like to know if the Datum Feature A and B are sufficient or should we add a Datum Feature C on a part like this?

Thank you.

Regards,

 

[greenimi]

Which feature is datum feature C?
Whcih standard are you using?

 

[Belanger]

A datum C isn't needed. It's all about the "six degrees of freedom." The only thing a datum C would constrain is rotation, and that is irrelevant since the profile callout goes all around, and thus self-relates all of the orientation (the many right angles, etc.).

As an aside, be sure to change the position symbol on that center hole to perpendicularity.

 

[nry67]

Hi Beranger..

Thank you for your come back.
Now I have complexed the drawing.
I ask the same thing concerning the information relate to the profile between the point C and G.

Regards,

 

[drawoh]

nry67,

Your first diagram, as shown, does not control rotation. Technically, this does not matter since the only rotatable feature is your outline. If someone else modifies your design, will they notice that you have not controlled rotation?

On your second diagram, your slots require a datum feature[ ]C that controls rotation.

--
JHG

 

[AndrewTT]

If you employ the same datums, in the same order, with the same boundary conditions for all of your profile FCFs the rule of simultaneous requirements will allow you to avoid the use of a clocking datum feature (section 4.19 ASME Y14.5-2009).

If you are following ASME Y14.5 for this part there are some other concerns:
1) As shown, the multiple single segment profile FCF does not follow the required format and is therefore meaningless. See sections (8.6 & 8.7).
2) What distinguishes the datum feature A side of the part from its opposite side? The section view makes this part appear symmetrical.

 

[nry67]

Hi,

Thank you for your response, you have comfort my point of view concerning the information on this Drawing.
Now, I need to found a good argument to convince the designer to update her drawing.

Regards,