Does "Diameter" Automatically Imply "Circle"?

[hogheavenfarm]

This is a new one for me. We have a requirement that indicates a minimum diameter for a shape which is not quite round. The situation is this. A round bar stock transitions to a teardrop shaped support pad. The requirement has a minimum diameter given, but the bar stock is transforming into a trapeziod shape at the point where the bar stock meets the teardrop "point". We have a situation where the bar elongates slightly to accomodate the transition. The customer argues that the entire bar should stay circular, but this would not transition to the pad. We contend we meet the intention of the diameter even if the transition area is not perfectly "round". The prints are unclear in this area (no dimensional information is given).
I have seen diameter definitions that say a line between to circumference points that passes through the center of a circle. This implies a circular link, but I have also seen definitions that say a line that passes through the center of a figure, implying other than a circle.

[SteelMaiden]

The diameter would be for the portion of a circle (arc) in that shape. Just like an elipse has multiple radius points, the entire shape is mad up of arcs with varying diameters.

[bobdoering]

In Reply to Parent Post by hogheavenfarm

I have seen diameter definitions that say a line between to circumference points that passes through the center of a circle. This implies a circular link, but I have also seen definitions that say a line that passes through the center of a figure, implying other than a circle.

A diameter can be used to define a perfect circle (no roundness), but all natural circular features must be defined by a diameter and a zone of tolerance of some sort (usually roundness.) But, a circle is a 2 dimensional feature. Add a third dimension, then you need to toss in cylindricity and taper - and that is if you are attempting to project the circular feature through space along one axis. Distort that circular feature across the third dimension, and even if you went simply to oval you now have two foci - not a center and diameter.

Your customer is either envisioning something not physically possible, or not accurately expressing what they really need. Not enough evidence to know for sure.

[Jim Wynne]

In Reply to Parent Post by hogheavenfarm

This is a new one for me. We have a requirement that indicates a minimum diameter for a shape which is not quite round. The situation is this. A round bar stock transitions to a teardrop shaped support pad. The requirement has a minimum diameter given, but the bar stock is transforming into a trapeziod shape at the point where the bar stock meets the teardrop "point". We have a situation where the bar elongates slightly to accomodate the transition. The customer argues that the entire bar should stay circular, but this would not transition to the pad. We contend we meet the intention of the diameter even if the transition area is not perfectly "round". The prints are unclear in this area (no dimensional information is given).
I have seen diameter definitions that say a line between to circumference points that passes through the center of a circle. This implies a circular link, but I have also seen definitions that say a line that passes through the center of a figure, implying other than a circle.

In addition to the good responses so far, I wonder if the disagreement is academic or actually related to the function/design intent of the product. It's not especially helpful to argue about a condition which, if corrected, wouldn't make any difference. I suggest that you get together with the customer's engineer(s) and (A) determine whether the condition is actually important or not, and (B) the best way to proceed in view of (A) and the reality of your manufacturing process.

[hogheavenfarm]

Good responses, I agree. As usual, I am in the difficult position of "retro-guessing" someones previous interpretation of the issue. Of course, now it is a problem, and redesign or revision is not possible. It boils down to a battle of sematics at this point. I just wanted to understand any possible interpretations of this. The correct thing would have been to explain all this to the customer years ago, and get an FAI sign off or some other blessing on the part. Now there is little to do that is constructive.