Metric thread sizes

Metric thread dimensions

Under the term dimensions of metric threads lie the parameters defining the diameter, pitch and thread profile geometry. In power hydraulics, metric threads are among the most commonly used, both in hose ends and in fittings or machine components.

Types of metric threads – a guide to threads used in hydraulics

In power hydraulics, choosing the right thread is crucial for ensuring tightness, durability and compatibility of connections. One of the most commonly used thread standards is the metric thread — simple, universal and well-known in the European industry. Below we present the most important information about the types of metric threads, their features and applications in hydraulic systems.

What is a metric thread ? 

Metric thread (denoted by the symbol M) is a thread whose nominal diameter and pitch are given in millimeters. Example designations include M10 × 1,5, where „10” is the outer diameter of the thread in mm, and „1,5” is the thread pitch (distance between adjacent turns, also expressed in mm). Metric threads can occur in versions: coarse — typical pitch, commonly used in mechanical designs, fine — smaller pitch, more turns per unit of length — used where greater precision or stronger connection is needed, left-hand thread — used in specific rotational conditions when we want to prevent self-loosening of the connection. The construction of a metric thread is based on a 60° profile angle, which is the standard in most industrial applications.

Types of metric threads in hydraulics

Straight metric thread (M). This is the most basic variant — a thread with a constant diameter and pitch, used in nuts, bolts and hydraulic components. Its advantage is simplicity and universality. In many hydraulic fittings (especially with tube connections or in screw-in connections) metric threads according to DIN 13, ISO 261/ ISO 965 or EN 60423 standards are used.