A hidden line in engineering drawing is a specific type of line used to represent edges, surfaces, or corners of an object that are not directly visible from the viewer's perspective.
Purpose and Characteristics of Hidden Lines
Hidden lines serve a crucial role in communicating the complete geometry of an object in a 2D engineering drawing. They provide information about features located behind other visible features. Key characteristics include:
- Line Style: Hidden lines are typically represented as a series of short, evenly spaced dashes. These dashes are generally about 1/8 inch long with 1/16 inch gaps.
- Line Weight: Hidden lines are typically of medium weight, less prominent than visible object lines (also known as outline or object lines).
- Meaning: They indicate the presence and location of features that are obscured by other parts of the object.
- Usage: They are used to improve the clarity and completeness of the drawing, helping viewers understand the object's shape and internal structure.
Importance in Engineering Drawings
The accurate representation of hidden lines is essential for several reasons:
- Completeness: They ensure that all features of the object are represented, even those that are not directly visible.
- Clarity: They improve the clarity of the drawing by providing context and spatial relationships between different features.
- Manufacturing: Manufacturers rely on hidden lines to understand the complete design of a part, enabling them to produce it accurately.
- Troubleshooting: Engineers use hidden lines to diagnose problems or analyze the behavior of a system, by understanding the internal structure.
When to Omit Hidden Lines
While hidden lines are generally important, there are situations where they might be omitted to reduce clutter and improve readability. For example:
- Isometric Views: Sometimes omitted in isometric views to reduce visual clutter.
- Simple Geometries: If the presence of a hidden feature is easily inferred from the visible lines, the hidden lines may be omitted.
- Overlapping Lines: When many hidden lines overlap, it can become difficult to interpret the drawing. In such cases, some hidden lines may be omitted or simplified.
Example of Hidden Line Usage
Imagine a box with a hole drilled through one side. In a drawing of this box, the edges of the hole on the far side (the side not visible) would be represented using hidden lines. This indicates the presence, size, and location of the hole, even though it cannot be seen directly.
Summary
Hidden lines are essential elements in engineering drawings, providing critical information about obscured features. Their proper use enhances the clarity, completeness, and overall usefulness of the drawings, aiding in manufacturing, analysis, and communication.
