Doubt on parallelism to control the point 1

[Vimalmechs]

PFA.
Function of the assembly:
ITEM 2 is spherical shaped. It is assembled inside the flat bottom hole feature of ITEM 1 (REFER HATCHED LOCAL SECTION AREA).I want the top contacts points of spherical ball within “.0005”. The plane derive from the three points should be within “.0005” parallelism with respect to datum A.

I have applied parallelism GD&T frame. I have seen the application of parallelism on diameter to keep diameter central axis parallel to the datum. But I haven’t experienced the parallelism to control the point.

Here my doubt is
1)It is a right approach of GD&T to achieve my function?
2)Is there any alternate approach to achieve this?

Anyone please clarify me.
Vimal VV

 

[pmarc]

First idea that comes to my mind is to control tangent plane derived from the highest points of 3 balls. Draw a plane on the drawing (seen as a vertical line in left view for example) and apply a geometric tolerance to it. If you are interested in controlling plane's parallelism to datum plane A as well as its distance to A, use profile of surface callout wrt A with (T) modifier. If parallelism is the only concern, use parallelism callout modified by (T) wrt A. I think it would be also reasonable to add an extra note clearly specifying which features the tangent plane is derived from.

 

[fsincox]

I agree that a tangent plane defined from the top of the balls is what you seem to be indicating you want. Parallelism is not a sutable for location though.
Frank

 

[fsincox]

pmarc,
Do you see any issue with tangent plane profile to do something like this?
Frank

 

[pmarc]

Not really, Frank.
Like I said, I would just make sure that the drawing clearly specifies which features forms the tangent plane.
Do you see anything?

 

[fsincox]

pmarc,
I agree!
Sorry, you had it covered.
Frank

 

[Vimalmechs]

Hi,

Sorry for the late response.Tangent modifier with parallelism full fills my requirement.

In between i got a doubt, 1)I am deriving my imaginary plane from 3 tangent points.its a plane, its not an irregular surface. So is it right approach to use "PROFILE GD&T".

Thank you all
Vimal VV

 

[pmarc]

Nothing wrong in using profile of surface with (T) modifier.
In fact parallelism modified by (T) controls perfect plane too.

 

[Vimalmechs]

Thanks pmarc.

 

[fsincox]

pmarc,
Really, I was questioning the use of parallelism with a basic dimension for location, here?
Frank

 

[pmarc]

Frank,
If Vimalmechs decides to use parallelism, location of tangent plane will not be controlled at all, thus basic dimension will be meaningless. Only if profile of surface is applied, basic dimension will make sense.

 

[fsincox]

pmarc,
Thanks
Frank