Alphabet of Lines

Drafting as a Language: Drafting conveys ideas clearly and concisely through symbols that indicate shape, size, material, finish, and assembly. Precision in drawings fosters clear communication between designers and producers, critical in graphic communication, where visual representations often express ideas more effectively than text.

Alphabet of Lines: Developed by ASME to classify line types in drawings based on thickness:

• Thick Lines: 0.7 mm to 0.9 mm mechanical pencil.

• Thin Lines: 0.3 mm to 0.5 mm mechanical pencil.

Line Types:

• Construction: Light lines for layout (0.5 mm pencil).

• Visible/Object: Thick, solid lines (0.9 mm) for object edges.

• Hidden: Medium dashed lines (0.7 mm) for hidden surfaces.

• Center: Thin alternating dashes (0.5 mm) for symmetrical features.

• Section: Thin cross-hatching at 45°, indicating materials or parts.

• Dimension, Extension & Leader: Thin lines with arrowheads for sizes or locations.

• Cutting Plane: Thick lines (0.9 mm) for imaginary cuts.

• Break Lines: Shorten views for repetitive details; varying thicknesses.

• Phantom: Indicate alternate positions/motion with very thin lines.

Hierarchy of Line Precedence: Determines the represented line type when overlaps occur, ranked as:

1. Object/Visible Line

2. Hidden Line

3. Cutting Plane Line

4. Center Line

5. Break Line

6. Dimension & Extension Lines

7. Sectioning Lines

8. Line Coincidence

Examples: Object lines take precedence over hidden lines in overlaps, and always draw the line with the highest precedence.