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Fastener knowledge: Thread six elements

 Tooth type thread is used to determine the geometry of the thread, the thread elements include, tooth, large, (medium and small) diameter of five elements, lines, lead, job rotation and height, only the six the same internal elements, external thread screwed to each other.

       1, tooth type: On threaded axial cross-sectional contour shape is called a thread tooth type. Between two adjacent tooth flank angle is called angle type. Tooth type commonly common thread is triangular, tooth-type angle of 60 °.

       2, large diameter, small diameter and diameter: refers to the large diameter and the crest of the external thread, internal thread teeth bottom coincides imaginary cylinder or cone diameter, externally threaded large diameter d with said internal thread large diameter represented by D. Trails and tooth bottom refers to the external thread, internal thread crest coincides with an imaginary cylinder or cone diameter of the small diameter d1 external thread, said internal thread of the small diameter D1 representation. Between the large diameter and small diameter, Imagine a cylinder (or cone), in its cross-sectional axis, prime line width and tooth width equal to the diameter of the imaginary cylinder diameter is called with d2 ( or D2) represented.

       3, lines: formationScrew threadThe number of lines is called a spiral. There are single-line and multi-line thread points, multiple thread in cross section perpendicular to the axis is uniformly distributed.

       4, lead: two adjacent teeth in the line corresponding to the diameter of the axial distance between two points is called the pitch. With a helix, two adjacent teeth in the line corresponding to the diameter of the axial distance between two points is called the lead. Relationship line number n, the pitch P, between the lead S: S = n · P

       5, rotation: the axial direction, clockwise rotation of the threaded become right-handed thread, the thread counterclockwise rotation is called left-handed thread.

       6, the working height: partially overlap each other in the distance perpendicular to the thread axis of the two mating thread profile. In addition to the nominal diameter of the threaded pipe thread with an inner diameter of the pipe nominal diameter, the outer diameter of the rest are in nominal diameter. Thread is standardized, there are metric (metric) and inch two kinds. International Standard Metric, China also used metric.

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