Segment Pro Outer Diameter Math Error?

[David Muehlbauer]

I finished some rings that I designed in Segment Pro and the diameter didn't match what the Summary report said. I checked everything and when I did the math manually I found that the outer diameter didn't match what SP said. I have attached the spreadsheet I created to analyze the difference, and I used Excel's representation of Pi (not 3.1416). The difference is 2-3% on each row.

What am I missing here?

 

[mfisher]

You will have to ask Lloyd for what numbers he is using for Pi and what formula that used for calculating SEL.
I would suggest you contact him by email.

Most turners I know pad the diameters. If you are wanting a 6 inch ring, you make a 6.125 or 6.25 inch ring. In the design you add width to allow turning down to the desired 6 inch. I have noticed that WTP and SP don't always have the same number. But we are talking such a small number difference.

 

[Jeff Miller]

I finished some rings that I designed in Segment Pro and the diameter didn't match what the Summary report said. I checked everything and when I did the math manually I found that the outer diameter didn't match what SP said. I have attached the spreadsheet I created to analyze the difference, and I used Excel's representation of Pi (not 3.1416). The difference is 2-3% on each row.

What am I missing here?

I'm wondering if SP is calculating the ring with the "tips" cut off to get a true circle, while the excel formula is going tip to tip, or maximum circumference.