Feature Control Frame is applied to the end of a Cylinder - Datum Dilemma

[optomist1]

Hi To All Covers,

I have a problem where, the following Feature Control Frame is applied to the end of a cylinder, a planar datum C, the FCF is a 0.2 perdendicularity control, referenced to Datum A-B (an axis datum established by circular and cylindrical datum targets) and to Datum C??? If Datum C is perdendicular to Datum A-B, why the self Datum??? What does the Datum C reference yield??

Puzzled....thanks for your assistance.

Regards,
Marty

[Stijloor]

In Reply to Parent Post by optomist1

Hi To All Covers,

I have a problem where, the following Feature Control Frame is applied to the end of a cylinder, a planar datum C, the FCF is a 0.2 perdendicularity control, referenced to Datum A-B (an axis datum established by circular and cylindrical datum targets) and to Datum C??? If Datum C is perdendicular to Datum A-B, why the self Datum??? What does the Datum C reference yield??

Puzzled....thanks for your assistance.

Regards,
Marty

Marty,

From Advanced Concepts of GD&T by Alex?

Stijloor.

[optomist1]

Hi Stijloor,

Sorry for the late response.....preparing for a new position, and studying for the GD&T test, yes it is Alex's text, waiting for access to a scanner then I'll upload it. If you have access to Alex's Advanced Concepts of GD&T text, see page 15-8, figure 15-7, I may have figured it out, but would appreciate a little Stuart Smalley affirmation. I beleive the answer is that when Datum Targets are used (in this case Circular Line and Cylindrical Area) to establish a Primary Datum/Axis, any Feature Control Frame that references the Primary Datum needs to include a Secondary Datum..in this case Planar Datum C is the Secondary Datum....

On page 15-10 Figure 15-9 a similar situation is present; in this case only Datum Target Points (3 ea at one end and 3 ea at the other end) are used to establish a Primary Datum Axis. In this case any Feature Control Frame that references the Primary Datum, Secondary and Tertiary Datums are needed.

Took a little digging but I think I have it...

Thanks for your assistance.

Marty

[optomist1]

Hi Stijloor,

Attached are the two previously mentioned figures.....

Thank you for your input...

Marty