This standard specifies the limit deviations of linear dimensions and angular dimensions of sewing machine parts without tolerances on the drawings, and linear or angular dimensions formed by mechanical processing after the parts are assembled. This standard applies to the dimensions of sewing machine parts processed by cutting, and also to the dimensions of non-cutting. QB/T 1512-1992 Limit deviations of dimensions of sewing machine parts without tolerances QB/T1512-1992 Standard download decompression password: www.bzxz.net

Light Industry Standard of the People's Republic of China
Limit Deviations of Dimensions without Tolerances for Sewing Machine Parts QB/T 1512-. 1992
-Part 1: Linear Dimensions and
This standard refers to and adopts the international standard IS02768-1:1989 "General Tolerances for Dimensions without Tolerances - General Tolerances for Angular Dimensions".
Subject Content and Scope of Application
This standard specifies the limit deviations of linear dimensions and angular dimensions without tolerances on sewing machine part drawings and linear or angular dimensions formed by mechanical processing after the parts are assembled. This standard applies to the dimensions of sewing machine parts processed by cutting, and also to the dimensions of non-cutting processing. 2 Reference Standards
GB/T1804 Tolerances and Fits Limit Deviations of Dimensions without Tolerances 3 Terminology
3.1 Linear Dimensions
The distance between two corresponding points on the surface of a part is generally measured by the two-point method. Such as the outer dimensions, inner dimensions, step dimensions, diameter, radius, distance, fillet radius and chamfer height of the parts. 3.2 Angular dimensions
The angle formed by two sides or two planes of a part, the angular dimension expressed in plane angle units, which only limits the direction of the line and the line on the surface, and does not limit the shape of each point on the line. For example, the dimensions marked with angles on the part drawings also include dimensions that are usually not marked with angles (such as right angles or angles of equipolygons).
4 Basic provisions
4.1 Provisions for limit deviation values
The limit deviations of linear dimensions without tolerance (excluding fillet radius and chamfer height of edges) shall be selected according to Table 1. Table 1
Basic size segmentation
>3～6
>6～30
>30～120
≥120~400
>400～1000
>1000～~2000
Approved by the Ministry of Light Industry of the People's Republic of China on June 8, 199284
Value, mm
Implementation on February 1, 1993
QB/T1512-1992
Note: (0) When the basic size is less than 0.5mm, the deviation value should be marked after the basic size. ② The tolerance band of the untoleranced dimensions in this standard adopts a symmetrical distribution with the basic dimension as the distribution center, so the limit deviation value in the table is the symmetrical deviation IT (below)
③ The letter code of the tolerance grade in the table (the same below): f—precision grade m medium slow coarse precision grade-extra coarse grade. 4.1.2 The limit deviation of the edge fillet radius and chamfer angle untoleranced dimensions shall be selected according to Table 2. Table 2
Basic size segmentation
>3～6
6 and above
Note: When the basic dimension is less than 0.5mm, the deviation value shall be marked after the basic dimension 4.1.3 The limit deviation of the angle untoleranced dimensions shall be selected according to Table 3. Table 3
Basic size segmentation of short side
>10~50Www.bzxZ.net
>50～120
>120～400
Above 400
±20″
Value, mm
Deviation value, mm
Note: ①The values ​​specified in the table are not applicable to the unnoted tolerance values ​​of 90 right angles. ②The values ​​specified in the table are applicable to the unnoted tolerance values ​​of inclination. 4.2 Selection of tolerance grade
±30°
When there is no special requirement for part accuracy, it can be selected from f, m, C, grades as needed. If this standard is inconsistent with the professional process standard, it shall be implemented in accordance with the provisions of the professional process standard.
Select f grade within the following machining size range. Unnoted tolerance dimensions as process benchmarks; unnoted matching dimensions,||tt| |The center distance between two holes without tolerance! The hole diameter without tolerance.
Select M grade if it falls within the following range
Except for the items specified in Article 4.2.1, the other dimensions that need to be machined without tolerance; the dimensions that are not machined without tolerance of precision castings, die castings, precision stampings, precision forgings, and plastic parts. Select C grade if it falls within the following range.
The dimensions that are not machined without tolerance of cold heading parts, embossed parts, and powder metallurgy parts; the dimensions that are not machined without tolerance of general castings and general stampings with a maximum size less than 200mm. Select V grade if it falls within the following range.
QB/T1512-.1992
a. The dimensions that are not machined without tolerance of free forgings; b. The dimensions that are not machined without tolerance of general castings and general stampings with a maximum size greater than 200mm. 4.3 Inspection and evaluation
The limit deviation of the dimensions without tolerances in the drawing shall not be included in the routine inspection of the production workshop or factory enterprise. Only when a dispute occurs shall the inspection and evaluation be carried out in accordance with the provisions of this standard. If an occasional deviation is found, it shall not be rejected as long as it does not damage the function of the part, unless otherwise specified.
4.4 Marking method
4.4.1 The number of this standard and the code of the tolerance grade can be marked on the drawing 1. Example: The middle tolerance grade should be marked with QB/T1512-m4.4.2 When this standard is to be selected in the technical documents, the number and code of the tolerance grade of this standard shall be quoted. The limit deviation of the dimensions without tolerances is shown in Appendix A.86
QB/T1512
Appendix A
The limit deviation of the dimensions without tolerances in the part drawing Tolerance dimension legend
(reference)
A1 The unindicated tolerance dimensions of the part drawing are shown in Figure 1. The symbols and numbers in the dotted circle in the drawing represent the limit deviation values ​​of the unindicated tolerance dimensions of the part related to linear dimensions, edge fillet radius, chamfer height and angle.
1X45°
Straight grain! =0.6
Additional instructions:
This standard is proposed by the Quality Standards Department of the Ministry of Light Industry. This standard is under the jurisdiction of the Quanrun Sewing Machine Standardization Center. This standard was drafted by the South China Sewing Machine Factory. The main drafter of this standard is Li Song.
R0.5±0.2
SR1040
1×45°
1(±0.21)
884989
8×±8/6s
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