What is thread?

Definition

Thread is a spiral – shaped continuous convex portion made on the surface of a cylindrical or conical matrix, with a specific cross-section.

On the surface of a cylinder or cone, a continuous convex with a prescribed tooth shape is formed along the spiral line. The convex is the solid parts on both sides of the thread, is thread tooth.

Geometry Parameters

– Major Diameter: The diameter of the imaginary cylinder that coincides with the crest of the male thread, or the root of the female thread.

– Minor Diameter: The diameter of the imaginary cylinder that coincides with the root of the male thread, or the crest of the female thread.

– Pitch Diameter: The diameter of the imaginary cylinder, which is the cylinder as the generatrix passes through the thread tooth, with the same width of the convex and groove.

– Thread Pitch: The axial distance between two points on the pitch diameter line adjacent tooth.

– Thread Lead: The axial distance between two points on the pitch diameter line adjacent tooth on the same spiral line.

– ncluded Angle: The angle between two adjacent flanks on the thread tooth.

– Lead Angle: The angle between the tangent of spiral on the pitch diameter cylinder and plane perpendicular to the axis of the thread.

– Length of Thread Engagement: The connection length of two matched threads.

Classification

– According to the shape of its matrix, it is divided into parallel thread and taper thread.

– According to the shape of the tooth, it is divided into triangle thread, rectangular thread, trapezoidal thread, sawtooth thread, etc.

– According to the sealing, it is divided into sealed thread and non- sealed thread.

– According to the direction of the helix, it is divided into right hand thread and left hand thread.

– According to the quantity of the helix, it is divided into single-start thread, double-start thread, and multi-start thread.

– According to the size of the tooth, it is divided into coarse pitch thread and fine pitch thread.

– According to the different occasions and functions, it is divided into fastening thread, pipe thread, transmission thread, special thread, etc.