Which way is more correct for dimensioning of the rectangular symmetrical feature?
1 Answer
Think in terms of tolerancing. Each individual dimension holds its respective geometry within specific tolerance limits. The left figure holds the right hand edges to a tighter tolerance than the left hand edges. Whereas the right hand figure holds the centerline of the whole geometry to a tight tolerance but allows both edges to vary even more due to their tolerances.
How you dimension it does not have a particular correct or preferred method. Each is equally correct. But what matters is how it is to be fabricated and then used that determines the proper dimensional order and tolerancing.
Also, you need to consider how you will actually measure the part to see if the geometry matches the given dimensions. In the case of the left hand figure it is quite easy to measure between the hard edges of the given geometry. In the case of the right hand figure you have dimensioned to a centerline floating in midair that has no hard geometry to measure to.
