Lines GOST 2.303 – 68 

GOST 2.303-68 establishes 9 types of lines depending on their thickness, image and main purpose.

The thickness of the lines in the drawing should be a multiple of the selected thickness of the solid main line, the thickness of which can vary from 0.5 to 1.4 mm. The thickness of the lines should be the same for all images in this drawing, which are drawn on the same scale.

The length of the strokes in the dashed and dash-dotted lines is chosen depending on the size of the image. The strokes in the line and the gaps between them should be the same length.

Dash-dotted lines should begin, intersect and end with strokes. Dash-dotted lines used as center lines are replaced with solid thin lines if the diameter of the circle or the dimensions of other geometric shapes in the image are less than 12 mm. The center of the circle is in all cases determined by the intersection of the strokes.

In complex sections and cross-sections, it is allowed to connect the ends of an open line with a dash-dotted thin line. The length of the ends of the open lines is chosen within 8 - 20 mm, depending on the size of the image. The main lines (visible contour lines) should be drawn with a thickness of 0.8...1.0 mm., dashed lines (invisible contour lines) - 0.4...0.5 mm., and the rest - 0.25...0.30 mm.