Impeller help

[[Ma...]]

I have an impeller. Six helical blades tapering to the top. I need to find the diameter of the blades at the bottom and at the top. I created a cross section thru the bottom to start. How do find that diameter?

I have tried maximum coordinate in polar and then made a circle out of those points but it doesn't put it where I thought it would 

I am open to any and all advice.

[[Ma...]]

To clarify, I created 2d curves on the cross section around the tip of the blades, but don't know how to isolate the most radial distance on the curve in order to pull it into a circle.

[[Ri...]]

With Curve - you can use the Maximum Coordinate, and isolate the axis, but you'd need for it to live inside of an alignment that is rotated to the blade. 

[[Ch...]]

Multiple ways to skin this cat.  I work with these all the time and can give you some tips.

First off, There's better ways to get that OD than a cmm.  Something like an OptiCline or a custom gage like we have.  

But if you have to get on a cmm there's a few things you can try.  Like Richard said, you can make an alignment that is clocked to each blade.  This is possible but kinda sucks too.  Clock the alignment to a symmetry point made from points on either side.  

OR

what I recommend is measuring multiple blades with curves.  Then recall those individual curves into another curve.  Then you can use a circle with Max Inscribed or Min Circumscribed to give you a diameter.  

Like this: We have a complex shaped curve, and the circle is just fitting around the outside for the OD.