Technical Drawing Lines Definitions

Lines in Technical Drawing - Definitions

• Line A geometric object with a length at least half its width that joins an initial point to a final point either continuously or discontinuously, curved or straight, with the initial and final points possibly coinciding (e.g., a circle).
• Line Element A simple part of a discontinuous line, such as spaces, points, and dashes.
• Line Segment A grouping of two or more line elements forming a line, for example, "space-dash."
• Indicator Line A line that accompanies a feature of a piece or view with additional information.
• Reference Line Vertical or horizontal lines used as baselines to display information.

Types of Lines

• Continuous Line Used for imaginary junctions of two curved surfaces, dimension lines, auxiliary dimension lines, indicator lines, reference lines, hatching, rotated section outlines, short center axes, fillet core, screw thread origin and end, dimension line diagonals, cross-section indication, fold lines, section details, indication of repeated details, calibration plane indicator, sheet position, and projection lines.
• Thick Continuous Line Used for visible edges and outlines, thread crest, thread length limit, representation of diagrams, maps of reticular metal structures, separation of matrices in piece views, cut and section arrow lines.
• Thin Dashed Line Used for invisible edges and outlines.
• Thick Dashed Line Used to indicate surface treatments, such as heat treatment.
• Thin Long Dash, Point Line Used to indicate axes, symmetry axes, primitive gear circumference, center hole circumference.
• Thick Long Dash, Point Line Used to indicate limited areas of surface treatment and plane cutting positions.
• Thin Long Dash, Double Point Line Used to indicate adjacent pieces, extreme positions of moving parts, center axes, developments prior to shaping, parts in front of a cutting plane, displacement zones, outline of the finished part within the rough piece being machined, framing of particular zones and projected tolerance zones.
• Thick Long Dash, Double Point Line Used to indicate adjacent pieces, extreme positions of moving parts, center axes, developments prior to shaping, parts in front of a cutting plane, displacement zones, outline of the finished part within the rough piece being machined, framing of particular zones and projected tolerance zones.
• Thin Long Dash, Triple Point Line Used to indicate adjacent pieces, extreme positions of moving parts, center axes, developments prior to shaping, parts in front of a cutting plane, displacement zones, outline of the finished part within the rough piece being machined, framing of particular zones and projected tolerance zones.
• Thick Long Dash, Triple Point Line Used to indicate adjacent pieces, extreme positions of moving parts, center axes, developments prior to shaping, parts in front of a cutting plane, displacement zones, outline of the finished part within the rough piece being machined, framing of particular zones and projected tolerance zones.
• Thin Long Dash, Short Dash Line Used for imaginary junctions of two curved surfaces, dimension lines, auxiliary dimension lines, indicator lines, reference lines, hatching, rotated section outlines, short center axes, fillet core, screw thread origin and end, dimension line diagonals, cross-section indication, fold lines, section details, indication of repeated details, calibration plane indicator, sheet position, and projection lines.
• Thick Long Dash, Double Short Dash Line Used for imaginary junctions of two curved surfaces, dimension lines, auxiliary dimension lines, indicator lines, reference lines, hatching, rotated section outlines, short center axes, fillet core, screw thread origin and end, dimension line diagonals, cross-section indication, fold lines, section details, indication of repeated details, calibration plane indicator, sheet position, and projection lines.
• Thin Dash, Point Line Used for imaginary junctions of two curved surfaces, dimension lines, auxiliary dimension lines, indicator lines, reference lines, hatching, rotated section outlines, short center axes, fillet core, screw thread origin and end, dimension line diagonals, cross-section indication, fold lines, section details, indication of repeated details, calibration plane indicator, sheet position, and projection lines.
• Thick Double Dash, Point Line Used for imaginary junctions of two curved surfaces, dimension lines, auxiliary dimension lines, indicator lines, reference lines, hatching, rotated section outlines, short center axes, fillet core, screw thread origin and end, dimension line diagonals, cross-section indication, fold lines, section details, indication of repeated details, calibration plane indicator, sheet position, and projection lines.

Line Dimensions (Normalized)

• Point Length: Half the thickness of the line
• Space Length: Three times the thickness of the line
• Short Dash Length: Six times the thickness of the line
• Long Dash Length: 24 times the thickness of the line
• Space Length: 18 times the thickness of the line

Line Thicknesses (Normalized)

• 0.1 to 1.2 mm
• 0.5 mm
• 0.8 mm
• 2.0 mm

Line Variations

• Wavy
• Spiral
• Zig-zag
• Freehand
• Double continuous line
• Continuous line with dashed line
• Continuous line with wavy line

Line Graphic Elements

• Example Graphic Elements

General Considerations

• Minimum space between two parallel lines: 0.7 mm
• Intersecting dashed lines should not intersect at their spaces.
• When placing a second line (e.g., to follow a contour), it should be located below or to the right of the original line.

Key Sources

• IRAM 45.000-02, 20, 22, and 24
• ISO 128