Mechanical drawings - Dimensioning
1 Scope
This part specifies the basic dimensioning methods in drawings.
This part is applicable to the drawing of mechanical drawings.
2 Normative references
The following documents contain provisions which, through reference in this part of GB/T 4458, constitute provisions of this part. For dated references, subsequent amendments to (excluding correction to), or revisions of, any of these publications do not apply. However, parties to agreements based on this part are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. For undated references, the latest edition of the normative document applies.
GB/T 1182 Geometrical tolerancing - Generalities, definitions, symbols, indications on drawings (eqv ISO 1101)
GB/T 4656.1 Technical drawings - Simplified representation of bars and profile sections (idt ISO 5261)
GB/T 14691 Technical drawings - Lettering (eqv ISO 3098-1)
GB/T 15754 Technical drawings - Dimensioning and tolerancing of cones (eqv ISO 3040:1990)
GB/T 16675.2 Technical drawings - Simplified representation - Part 2: Dimensioning
GB/T 18594 Technical product documentation - Lettering - CAD lettering of the Latin alphabet, numerals and marks (idt ISO 3098-5:1997)
GB/T 19096 Technical drawing - Drawing presentation - Vocabulary and indications for edges of undefined shape (ISO 13715:2000, IDT)
3 Basic rules
3.1 The actual size of the part shall be based on the dimension value indicated on the drawing, regardless of the size and the accuracy of the drawing.
3.2 If the dimensions in the drawing (including technical requirements and other notes) are expressed in mm, the unit symbol (or name) need not be marked; if other units are used, the corresponding unit symbol shall be indicated.
3.3 Unless otherwise stated, the dimensions of the part indicated on the drawing are the finished dimensions.
3.4 Each dimension of the part shall generally be marked only once on the figure that most clearly reflects the structure.
4 Dimension boundary line, dimension line and dimension value
4.1 Dimension boundary line
4.1.1 Dimension boundary lines, which shall be led out from the contour line, axis line or symmetrical centerline of the figure, or may be these lines (Figures 1 and 24), shall be drawn in thin solid lines.
Foreword i
1 Scope
2 Normative references
3 Basic rules
4 Dimension boundary line, dimension line and dimension value
5 Dimensioning symbols and abbreviations
6 Simplified dimensioning
7 Dimensioning for edges of undefined shape
Annex A (Normative) Dimensioning symbols and abbreviations
Figure 1 Drawing of dimension boundary line
Figure 2 Dimensioning of curve contour (I)
Figure 3 Dimensioning of curve contour (II)
Figure 4 Dimensioning for oblique intersection between dimension boundary line and dimension line
Figure 5 Drawing of dimension boundary line for indicating angle
Figure 6 Drawing of dimension boundary line for indicating chord length
Figure 7 Dimensioning for arc length
Figure 8 Dimensioning for arc length (with relatively large radian)
Figure 9 Arrow as terminal of dimension line
Figure 10 Oblique line as terminal of dimension line
Figure 11 Dimensioning when terminal of dimension line is in the form of an oblique line
Figure 12 Dimensioning for diameter of circle and radius of arc
Figure 13 Dimensioning when radius of arc is relatively large
Figure 14 Dimensioning when only one arrow is drawn on the dimension line of a symmetrical part (I)
Figure 15 Dimensioning when only one arrow is drawn on the dimension line of a symmetrical part (II)
Figure 16 Dimensioning at limited places
Figure 17 Indication positions for dimension values
Figure 18 Indication direction of dimension value
Figure 19 Indication of dimension value within the range of 30° tilt to the left
Figure 20 Indication of dimension value not in horizontal direction (I)
Figure 21 Indication of dimension value in horizontal direction (II)
Figure 22 Indication positions for angle values (I)
Figure 23 Indication positions for angle values (II)
Figure 24 Indication of dimension value not separated by any line
Figure 25 Dimensioning for sphere (I)
Figure 26 Dimensioning for sphere (II)
Figure 27 Dimensioning for reference dimension
Figure 28 Dimensioning for square structure
Figure 29 Simplified dimensioning for thickness of plate parts
Figure 30 Dimensioning when there are special requirements for radius
Figure 31 Dimensioning for 45° chamfers
Figure 32 Dimensioning for chamfers of not 45°
Figure A.1 Scale representation of symbols for dimensioning
Table 1 Dimensioning examples of slope and taper
Table A.1 Dimensioning symbols and abbreviations
