Centertocenter

Center-to-center (often written center-to-center distance or C-C distance) is the straight-line distance between the centers of two circular features on a part, such as holes, bosses, or shafts. It is a standard linear dimension used in mechanical drawings and manufacturing to specify spacing. It differs from edge-to-edge, diameter, or radius, because it measures the position of centers rather than the size of features themselves.

Usage: Center-to-center distances define how parts align in assemblies, determine mounting hole patterns, and control tolerance stacks in fit and assembly. In bolt patterns, the term describes spacing between hole centers; designs may reference the bolt circle diameter (BCD or PCD) to locate evenly spaced holes around a circle. For two holes on a plate, a center-to-center value of 40 mm means the holes' centers are 40 mm apart.

Measurement: The distance is found by locating the centers of the features and measuring the straight-line separation, typically with calipers, a coordinate measuring machine (CMM), or optical tooling. In circular patterns, the center-to-center distance between adjacent holes in a bolt circle of diameter D and n evenly spaced holes is L = D * sin(pi/n) or L = 2R sin(pi/n). Accurate CAD models and GD&T practices help ensure proper alignment and tolerance.