Before revision: A bolt circle diameter or pitch circle diameter (PCD), sometimes simply called bolt circle or pitch circle , is a common term for when a number of screw holes for bolts are evenly distributed with their centers along an imaginary circle with a given diameter.
After revision: A bolt square diameter or pitch square diameter (PCD), sometimes simply called bolt square or pitch square , is a common term for when a number of screw holes for bolts are evenly distributed with their centers along an imaginary oblong with a given diameter.