Skruvdiameter

Skruvdiameter, or screw diameter, is a key dimension used to describe the size of a screw’s threaded portion. It typically refers to the nominal size of the fastener and is used to determine the compatibility with mating parts such as nuts or tapped holes. In metric fasteners the diameter is shown with the M designation (for example, M6), while imperial fasteners use inch-based diameters.

There are several related diameters associated with a screw thread. The major diameter is the largest outside diameter of the screw threads and is usually what is referred to when stating the screw’s diameter. The pitch diameter is an abstract value where the thread height equals the space between adjacent threads; it is important for calculating effective thread engagement. The minor diameter is the smallest outside diameter at the base of the threads. For most practical purposes, the nominal or major diameter is used to designate the size of the screw.

Standards and designations help ensure compatibility. In metric systems, the designation M followed by a number indicates the nominal thread diameter (for example, M6, M10). The thread pitch—how far the thread advances in one turn—may vary, with common coarse pitches such as 1.0 mm for M6 or 1.5 mm for M10, and finer pitches available for specific requirements. In imperial systems, diameters are given in inches and paired with a thread pitch (for example, 1/4-20).

Measurement and tolerances are governed by standards that specify permissible deviations for both the screw and its mating hole or nut. Precision and fit requirements influence the chosen skruvdiameter, affecting strength, fatigue life, and assembly performance.