Lesson 3: Hidden Lines and Internal Features
Duration of Days: 3
Lesson Objective
Students will accurately represent non-visible edges using dashed hidden lines.
How do we show a hole inside a block without cutting it open?
What is the hierarchy of lines if an object line and hidden line overlap?
Hidden Line, Center Line, Center Mark, Precedence of Lines.
CT CTE.AR-D.1.1: Identify and use proper line types (Hidden/Center).
Students sketch orthographics of objects with drilled holes and internal slots.
Purpose: To learn how to communicate "invisible" geometry to a machinist or builder.
DOK Level: 3 (Strategic Thinking).
Use "X-Ray" diagrams where internal features are color-coded.
A drawing of a "Slotted Block" requiring hidden lines in at least two views.
Sample parts with internal cavities (e.g., a PVC pipe T-junction).