Overview
This lecture covers the main types of lines used in engineering drawings and blueprints, explaining their conventions and purpose for clear communication.
Types of Lines in Engineering Drawings
- Visible lines (object lines) are thick, solid lines representing the edges or outlines of objects.
- Hidden lines use short, evenly spaced dashes to show features not visible in a particular view.
- Center lines consist of alternating long and short dashes, marking symmetry axes or centers of holes.
- Section lines are thin lines indicating exposed surfaces in a sectional view, often varying pattern to show different materials.
- Dimension lines are unbroken lines ending in arrowheads, with the dimension itself written in between.
- Extension lines project from the object to indicate the starting and ending points of a dimension, usually with a visible gap from the outline.
- Leader lines are unbroken lines ending in arrowheads, used to connect notes or dimensions to specific features.
- Cutting plane lines mark where a sectional cut is made, with arrows pointing to the view direction after the cut.
- Viewing plane lines, similar to cutting plane lines but do not cut the part, are for showing helpful internal views.
- Long break lines, typically ruled lines with zigzags, indicate omitted portions of long objects like shafts or tubes.
- Short break lines are solid freehand lines used to represent breaks in smaller objects or to detail features.
- Phantom lines are composed of a repeating pattern (long dash, two short dashes), used for alternate positions, related parts, or repeated details.
Key Terms & Definitions
- Visible Line (Object Line) — Thick, solid line showing visible edges of an object.
- Hidden Line — Short dashed line used to show features not visible in the current view.
- Center Line — Long and short dashed line indicating axes of symmetry or centers of circles.
- Section Line — Thin line marking areas exposed by a sectional view.
- Dimension Line — Line with arrows indicating the measured length between two points.
- Extension Line — Line extending from the object to show the limits for a dimension.
- Leader Line — Arrowed line pointing to a feature for notes or dimensions.
- Cutting Plane Line — Line with arrows marking where a sectional view is taken.
- Viewing Plane Line — Line marking where an interior view is taken without a section cut.
- Break Line — Line indicating that part of the object is omitted for clarity.
- Phantom Line — Line with a specific dash pattern, showing alternate positions or repeated details.
Action Items / Next Steps
- Review examples of each line type in your engineering drawing textbook or handouts.
- Practice identifying and drawing each type of line on sample blueprints.