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42 basic knowledge of mechanical drawing

March 4, 2024

1. Paper formats can be divided into 5 types according to size. The drawing format codes are A0, A1, A2, A3, and A4. There must be a title bar in the lower right corner of the picture frame. The direction of the text in the title bar must be consistent with the direction of viewing the picture.


2. There are eight types of graph lines: thick solid line, thin solid line, wavy line, double polyline, dotted line, thin dot-dash line, thick dot-dash line, and double-dash line.


3. In the drawing, the visible contours of the machine parts are drawn with thick solid lines, the invisible contours are drawn with dotted lines, the dimension lines and dimension lines are drawn with thin solid lines, and the symmetry center line and axis are drawn with thin dotted lines. The width of the dashed line, thin solid line and thin dot-dash line is about 1/3 of the thick solid line.


4. Proportion refers to the ratio of the graphic size in the picture to the actual size.


5. Ratio 1:2 means that the physical size is twice the size of the graphic, which is a reduction ratio.


6. Ratio 2:1 means that the graphic size is twice the actual size, which is an enlargement ratio.