4.2.e. Line Types & Weights (ISO Standards)

Visible Solid thick (0.7–1.0 mm) Shows visible outlines/edges

A visible line is a solid line that is drawn thick, typically between 0.7 to 1.0 mm in weight. It is used to depict the edges and outlines of objects in technical drawings. This means that when you see a thick line in a drawing, it indicates that this is a boundary or edge that is clearly visible, helping the viewer understand the shape and details of the object being represented.

Imagine tracing the outline of a house using a marker. The bold, dark line you create represents the visible structure of the house, just as a visible line does in a technical drawing. It makes it easy for someone looking at your drawing to see the outline of the house without confusion.

Hidden Dashed medium Shows obscured (0.35–0.5 mm) edges/features

A hidden line is specified as a dashed line with a medium thickness, usually between 0.35 and 0.5 mm. This type of line is used to represent edges or features of an object that cannot be seen from a particular viewpoint, indicating that they are behind or beneath other surfaces. The dashed pattern visually indicates to anyone looking at the drawing that there are parts of the object that exist but are not visible in that view.

Think of a treasure chest that is partially buried in sand. The visible part above the sand represents what you can see (like a visible line), while the part below the sand is hidden from view—it exists but isn't seen. A hidden line in a drawing identifies this buried part, showing that there’s more to the chest than what is visible.

Center Long-short chain thin Axes, symmetry, hole centers (0.35 mm)

A center line is a thin line used to represent the axes of symmetry in a drawing, as well as the center points of features like holes. It typically has a long-short dash pattern and is drawn with a thickness of 0.35 mm. Center lines are crucial for understanding how to mirror features across a central axis or for identifying where specific measurements originate.

Imagine a seesaw that is perfectly balanced in the middle. The line that bisects the seesaw represents its center line, showing symmetry. Similarly, center lines in your drawings indicate where objects can be balanced or centered, making them essential for precise construction.

Section/Cutting Thick chain, arrowed ends Indicates where the view is cut

A section line uses a thick chain pattern with arrowed ends that indicates where the object has been 'cut' for the purpose of viewing its internal features. This is crucial for understanding complex shapes that cannot be fully appreciated from the outside. When you see this line in a drawing, it tells you that what follows is a view showing the inside of the object as if it has been sliced through.

Think about slicing a loaf of bread to see the inside. The cut reveals the loaf's texture and ingredients that are not visible from the outside. In technical drawings, the section line performs a similar role, guiding viewers through the inner workings of machinery or objects.

Dimension/Lead Thin continuous (0.35 mm) Denotes sizes and notes

A dimension line is a thin, continuous line typically set to a thickness of 0.35 mm. This line is used to denote measurements on drawings, indicating how long or high something is or providing notes to clarify dimensions. Dimension lines usually extend from the object to the measurement figures, clearly showing the size of features.

Consider measuring the height of a basketball hoop with a tape measure. The line that you can imagine extending from the hoop to the number indicating its height serves a similar purpose to a dimension line in a drawing, making clear exactly how tall the hoop stands.

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