dimension varies

I modelled flight screw in CREO version 6.0 .  for manufacturing purpose I need to flatten the flight. top surface of the screw is essential for manufacturing purpose, so I am using flatten quilt to get the flatten the surface and the surface as been flattened. I am using flatten quilt deformation I am able to project the divided segments from the helical screw to flatten quilt , but i did not get exact dimensions from the flatten and helical it varies around 10 to 15mm is there any possible way to get the exact dimension.

1.helical form

2.flatten form