GB/T 5796.4-1986 Trapezoidal thread tolerances

GB/T 5796.4-1986 Trapezoidal thread tolerances GB/T5796.4-1986 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Metric trapezoidal screw threads-TolerancesUdC 621.882
.082.4
GB 5796.4--86
Replaces GB 785-65
This standard applies to the trapezoidal threads specified in GB5796.1-86 "Trapezoidal thread profile" and GB5796.2--86 "Trapezoidal thread diameter and pitch series".
This standard is equivalent to the international standard ISO2903--1977 "ISO metric trapezoidal thread-tolerances". Tolerance zone position and basic deviation
1.1 The position of the tolerance zone is determined by the basic deviation. This standard stipulates that the upper deviation cs of the external thread and the lower deviation E" of the internal thread are the basic deviations.
1.2 For the major diameter D4, the middle diameter D, and the minor diameter D of the internal thread, a tolerance zone position H is specified (see Figure 1). Its basic deviation is zero. 1.3 For the middle diameter d2 of the external thread, three tolerance zone positions h (see Figure 2a), e and c (see Figure 2b) are specified. For the major diameter d and the minor diameter d, only one tolerance zone position h is specified. The basic deviation of h is zero, and the basic deviations of e and c are Negative value. Its original tooth type
Figure:
Internal thread major diameter:
7D—Internal thread minor diameter tolerance;
Internal thread pitch diameter:
-Internal thread minor diameter;
Internal thread pitch tolerance;
National Bureau of Standards 1986-01-21 Issued
Figure 1 Internal thread tolerance zone
Maximum solid tooth type
19870101 implementation
Figure: d External thread major diameter
-External thread pitch diameter;
GB 5796.4
The position of tolerance zone of major, medium and minor diameter is h
hThe position of tolerance zone of major and minor diameter is h, the medium diameter is cFigure 2 Tolerance zone of external thread
Basic tooth profile
Maximum solid tooth profile
Basic tooth profile
Maximum solid tooth profile
External thread minor diameter;
Pitch,
Basic deviation of medium diameter;
External thread major diameter tolerance,
External thread medium diameter tolerance;
External thread minor diameter tolerance.
GB 5796.4--86
1.4 The basic deviation values ​​of the middle diameter of internal and external threads are shown in Table 1 Table 1 Basic deviation of the middle diameter of internal and external threads
Internal thread
2 Tolerance zone size and tolerance grade
GB5796.4--86
2.1 This standard specifies the following tolerance grades for each diameter of internal and external threads; Diameter
Internal thread minor diameter D
External thread Thread diameter d
Internal thread pitch diameter D,
External thread pitch diameter d2
External thread minor diameter d
The tolerance values ​​of internal thread minor diameter are listed in Table 2. 2.2
The tolerance values ​​of external thread major diameter are listed in Table 3. 2.3
Table 2 Internal thread minor diameter tolerance Tp
4th grade tolerance
*6th grade tolerance is listed for calculating the tolerance values ​​of grades 7, 8, and 9. 278
Tolerance grade
7, 8, 9
(6)*7, 8, 9
Table 3 External thread major diameter tolerance T.
4th grade tolerance
GB5796.4-86
2.4The tolerance values ​​of internal and external thread pitch diameter are listed in Table 4 and Table 5 respectively. Among them, the tolerance values ​​of grade 6 of external threads are only listed as the tolerance values ​​of the middle diameter of grades 78 and 9. Table 4 Internal thread middle diameter tolerance TD,
Nominal diameter
Nominal diameter
GB 5796.4—86
Continued Table 4
Nominal diameter
GB 5796.4—86
Table 5 External thread middle diameter tolerance Td
Nominal diameter
2.5 The tolerance values ​​of the minor diameter of external threads are listed in Table 6. 282
GB 5796.4—86
Continued Table 5
Nominal diameter
GB 5796. 4—- 86
Table 6 External thread minor diameter tolerance Tds
Mid-diameter tolerance zone position is c
111 Minor diameter tolerance zone position is e Mid-diameter tolerance zone position is h Grade
Nominal diameter
3 Screw-in length
GB5796.4-86
Continued Table 6
Mid-diameter tolerance zone position is c Mid-diameter tolerance zone position is e Pitch
Mid-diameter tolerance zone position is h
3.1 This standard divides the screw-in length into two groups, N and L, according to the size of the nominal diameter and pitch. N represents the medium screw-in length and L represents the long screw-in length.
3.2 The values ​​of the screw-in length are listed in Table 7.
GB 5796.4-86
Table 7 Thread engagement length
Engagement length group
Nominal diameter d
Nominal true diameter d
Selection of thread accuracy and tolerance zone
GB 5796.4-86
Continued Table 7
Engagement length groupwww.bzxz.net
4.1 Since the standard only specifies one tolerance zone (4H, 4h) for the internal thread minor diameter D and the external thread major diameter: the standard also stipulates that the tolerance position of the external thread minor diameter d3 is always h, and the tolerance grade number is the same as the pitch diameter tolerance grade number, therefore, for trapezoidal threads, only the pitch diameter tolerance zone is selected and marked to represent the trapezoidal thread tolerance zone.
4.2 This standard specifies two types of precision for trapezoidal threads: medium and rough. The selection principle is: medium: general use,
rough: used when the precision requirement is not high. 4.3 In general, the middle diameter tolerance zone should be selected according to Table 8. 28
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