Lochkreismaß

Lochkreismaß is a term used in German engineering to describe the diameter of the bolt circle on a circular hole pattern. It is often called Lochkreismaß or Pitch Circle Diameter (PCD) in English. The concept is central to mounting interfaces such as vehicle wheels, brake rotors, flanges, and couplings, where bolts are positioned at regular intervals around a circle.

Definition and terminology

The Lochkreismaß D is the diameter of the circle that passes through the centers of all bolt holes in the pattern. The number of holes around the circle is the Lochzahl (for example, 4, 5, or 6). The Lochkreismaß together with the Lochzahl defines the geometry of the mounting pattern and determines compatibility between components.

Measurement and calculation

If the center-to-center distance between adjacent bolt holes (the hole pitch) is known for an n-hole pattern, the Lochkreismaß can be calculated as D = s / sin(π/n). In practice, the Lochkreismaß is usually specified by the component manufacturer or documented in standards. Direct measurement is possible with a caliper or a bolt circle gauge, or by tracing the pattern on the hub or flange and using the pattern documentation. The Lochkreismaß is distinct from the central bore (Mittenloch) or hub diameter, which serves a different function.

Common usage

Lochkreismaße are widely used in automotive wheels (for example, patterns like 4x100, 5x114.3, 5x112) and in mechanical assemblies such as flanges and rotors. Correct matching of Lochkreismaß and Lochzahl is essential for proper fit and safe operation.

Etymology and scope

The term reflects the diameter-based description of bolt patterns and is a fundamental specification in mating components with bolted connections.