Before describing the heat treatment of threaded fasteners, it is necessary to understand the basic profile, diameter and pitch, basic dimensions and thread tolerances of the threaded fasteners. Because the geometric accuracy of threaded fasteners after heat treatment cannot be lost. Before the manufacture of threaded fasteners, it is necessary to select materials according to the material characteristics and the requirements of use. What are the changes in the thread geometry when the heat treatment is required? What measures need to be taken to control the heat treatment deformation? These geometric and precision components of the thread are given specifications. The standard numbers are listed below:
GBT192-2003 ordinary thread basic tooth type
GBT193-1981 Ordinary Thread Diameter and Pitch Series
GBT196-2003 ordinary thread basic size
GBT197-2003 ordinary thread tolerance
Ordinary thread diameter and pitch series
The diameter and pitch of the thread are not randomly matched. Small diameter and large pitch and large diameter are obviously unreasonable. Therefore, the national standard GB/T193 specifies the diameter and pitch selection range of the common thread with a nominal diameter of 1-600mm. The nominal diameter has a preferred first series, a second series and a third series that are not used as much as possible, and a corresponding pitch. The pitch of ordinary thread is divided into coarse and fine teeth, ordinary thread with diameter ≤68mm, each diameter corresponds to one coarse pitch, and one or more fine pitches are available.
