bolt circle

{{engineering}} A theoretical circle on which the centerpoints of bolt holes lie when the bolt holes are positioned as equally spaced in a circle. Common examples are the bolt circle for the lugs on a car's wheel, or the bolts on a bolted joint between pipe flanges. Often abbreviated "BC" or "B.C." on engineering drawings. Often treated as a basic or reference dimension, unless true position for the centers is specified using GD&T.