Centerbor

Centerbor is a term used in mechanical engineering to describe a precision bore operation or tool designed to establish and maintain a central axis for a rotating part. The centerbor creates a central bore that serves as a reference for subsequent machining operations, ensuring concentricity with respect to features such as gear faces, hubs, or sleeves. The concept emphasizes an accurate initial alignment, typically achieved with a centering feature such as a center drill or locating pin that guides the cutting tool and minimizes runout during boring or reaming.

In practice, a centerbor may refer to either a specialized boring tool with an integrated centering tip or a carefully controlled sequence of center drilling followed by boring to final diameter. The result is a bore that is straight and coaxial with the workpiece’s established center, enabling reliable mounting of shafts, bearings, or other radial components.

Common applications include automotive wheel hubs, flywheels, machine tool spindles, and hydraulic or pneumatic housings where precise bore alignment is critical. Tolerances and surface finishes depend on the process, material, and equipment, ranging from rough production runs to high-precision assemblies.

Centerbor concepts intersect with standard bore practices and measurement methods such as dial indicators, bore gauges, and coaxiality checks. While the term centerbor may appear in some machining literature, it is often used interchangeably with general center-boring or bored-hole alignment techniques.