This standard specifies the dimension series of watch back covers with threads. This standard applies to watch back covers that are connected to the watch case by threads. QB/T 2400-1998 Dimension series of watch back covers with threads QB/T2400-1998 Standard download decompression password: www.bzxz.net

QB/T2400--1998
This standard is revised and adjusted to the industry standard based on the original national standard GB4045-1983 "Threaded watch back cover size series". During the revision process, the relevant technical elements were adjusted and modified. The main difference between this standard and GB4045---1983 is: the reference standard in Chapter 2 is added.
This standard is proposed by the Industry Management Department of the State Bureau of Light Industry. This standard is under the jurisdiction of the National Clock and Watch Standardization Center. The drafting unit of this standard: Dandong Watch Industry Company. The main drafters of this standard: Su Fusheng and Ren Liang. From the date of implementation of this standard, GB4045--1983 "Threaded watch back cover size series" will be abolished. 120
Light Industry Industry Standard of the People's Republic of China
Threaded watch back cover size seriesbzxz.net
This standard specifies the threaded watch back cover size series. This standard applies to watch back covers connected to the watch case by threads. 2 Referenced standards
QB/T2400—1998
The clauses contained in the following standards constitute the clauses of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T196—1981 Basic dimensions of common threads GB/T197—1981 Tolerances and fits of common threads GB/T1803-1979 Tolerances and fits to 18mm hole and shaft tolerance zone 3 Structural types
3.1 Regular polygonal back cover
3.1.1 Regular polygonal back cover can be divided into: ten-sided (Figure 1), twelve-sided (Figure 2) and fourteen-sided (Figure 3) regular polygonal back cover, and its part names and codes are shown in Figures 1, 2 and 3.
3.1.2 The sides of the regular polygon on the back cover can be straight lines or inward concave arcs. d
d,—thread outer diameter c—width across flats
3.2 Notch type back cover, part names and codes are shown in Figure 4. Approved by the State Bureau of Light Industry on November 25, 1998
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Implementation on June 1, 1999
4 Dimension series and tolerances
QB/T2400—1998
dt—Outer diameter of thread, d:—Inner diameter of slot; a—Length of slot; b—Width of slot—Depth of slot Figure 4
4.1 The dimension series and tolerances of regular polygonal back covers are shown in Tables 1 and 2. The upper and lower deviations shall be in accordance with GB/T1803 Table 1
(Ten sides)
M19x 0.5
M21×0.5
Note: The types in brackets are not recommended. Q
12 square
(14 square)
QB/T2400—1998
For the dimension series and tolerance of notch-type rear cover, please refer to Table 3 and Table 2. The upper and lower deviations shall be in accordance with GB/T1803. 4.2
4.3The basic dimensions and tolerances of the threads on the rear cover shall be in accordance with GB/T196 and GB/T197. -ii KAoNii KAca
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