Håldiameter

Håldiameter is a term used in mechanical engineering to denote the diameter of a hole or bore in a workpiece. It is a fundamental geometric parameter that determines how a component will mate with a shaft, pin, bolt, or bearing. The hole diameter, together with the corresponding shaft diameter, defines the fit type of the assembly—such as clearance, interference, or transition fit.

In standard practice, hole sizes and their tolerances are described according to the ISO system of limits and fits. Holes are designated with a letter class (commonly H), which indicates a zero or near-zero lower deviation, while shafts use corresponding lowercase classes (such as h). The interaction of hole and shaft tolerances establishes whether the parts will have a loose, tight, or intermediate fit. For example, a nominal 10 mm hole with H7 tolerance typically ranges around 10.000 to 10.015 mm in common tables.

Manufacturing processes to achieve a desired håldiameter include drilling, reaming, boring, and honing. The chosen process affects not only the nominal size but also roundness, straightness, and surface finish. After production, the diameter is verified with precision measuring tools such as bore gauges, plug gauges, or calibrated calipers, often at several axial positions to ensure proper concentricity and tolerance compliance.

On technical drawings, håldiameter is specified as a nominal size plus tolerance and is critical for ensuring proper assembly, interchangeability, and performance of mechanical systems. Accurate specification and verification of the håldiameter help prevent assembly issues and ensure reliable function of machinery and components.