Datum target points simulating V-block for planar rotation

[[Ja...]]

Hi,

I have a part with plane and circle for primary and secondary datums. But the tertiary datum for orientation of part is made of two datum target points on a OD circle on casting surface as if they are simulating a 90 deg V-block. See attached picture.
Now maybe I am overthinking this but to setup my alignment, I am using looped base alignment with plane for spatial and z, circle for x and y and using recall feature points into a symmetry point and using that symmetry point for planar rotation. Will this accomplish what I am trying to simulate?
I have also created a symmetry construction and an edge point using the datum target points. They can also be used for planar rotation, but the question is will looping this base alignment setup, align the part in the desired manner?

Any other suggestions or approaches that might work better on this?

Screenshot 2022-11-23 113208.jpg

[[Ma...]]

I used circles where i put only 3 touch points on each side - so 6 points. With restricted radius of course.

I tried radius-point, but it wasn't best choice.

[[Ro...]]

A V-block won't stop the rotation, so it does nothing as a tertiary datum.

My question is how are you loading the part into the V-block? If there are no rotational features that clock the part when you load it, and you just put it in any orientation, then again, the V-block does nothing as a tertiary. And if there are clocking features then they should be the tertiary.

I've seen V-block datum targets on older prints, but they usually control the centerline on the axis of the part, instead of using the ID.

If I'm misunderstanding and the V-block is perpendicular to the primary datum plane, then your method will work fine.

[[Ja...]]

Sorry for the confusion, the picture only shows the clocking feature (smaller cylinder). Actual bigger part is a simple cylindrical tube on the rim of which this smaller cylinder lies.
The smaller cylinder is a cast surface on which the two datum target points (90 degree apart) are defined at a specific height which locks orientation of part.

I am not actually using a V block to orient the part. I am probing these points manually and looping the alignment. I meant to say that these target points acts as if the part orientation will be locked by using a V-block arrangement on some fixture.

The question is how will you use these to setup your looped base alignment, as you can only use a single feature for planar rotation for normal base alignment setup. Will you recall points into one of these single features: 1) symmetry point; 2) symmetry construction, 3)Edge point? Or will you use some other alternate alignment method ( 3D best fit; geometry best fit) with looping ?

[[Ro...]]

Ok. Makes sense. 🙂

I would use a 3d line for clocking, recalling the center of the circle and the symmetry of the 2 datum targets. I'm not a fan of using single points for rotational constraint in alignments. I almost always use 3 lines in alignments because I rarely have alignments flip when using them.

Edited to add: The circle being your secondary datum.