Engineering Symbols Model Documentation

What is a Symbol? Symbol: An arbitrary or conventional sign used in writing or printing related to a particular field to represent operations, quantities, elements, relations or qualities.

Everyday Symbols

Technical Symbols

In this lesson: Symbols used in Engineering Drawings Linetypes Holes Screw thread notation

Linetypes Group 1 lines are used to define an object’s geometry and visible limits of a shape. Group 2 lines are meant to show an object’s size and place notes, where needed. Group 3 lines are used to define how an object is going to be cut or sectioned to clarify its description, a part’s movement or its relationship to another part.

Object Line Hidden Line Center Line Group 1:

Object lines showing the front view of this part View Direction Object Line

Hidden lines showing hidden details such as a hole or surface Hidden Line

Center lines showing center locations of circular geometry Center Line

Dimension Line Extension Line Leader Line Group 2:

2.5’ Dimension lines show the size of the shape of a part. { Dimension Line

2.5’ Extension Line Extension lines used in combination with dimension lines

Notes or dimensions can be added here, at the end of a leader line. Leader Line

Group 3: Break Line Cutting Plane Line Section Line Phantom Line

Break lines Break Line

Cutting Plane Line

Section lines indicating surfaces cut by cutting plane line Section Line

Phantom lines: Phantom lines showing the path of a bouncing ball

Holes Drilled Countersink Counter bore

Diameter Depth Drill Hole

Diameter Depth Countersink Countersink Hole

Diameter Depth Counterbore Counterbore Hole

Screw Threads: Diameter Type of Thread Class of fit

Everyday Symbols

References: Hammer, W. (1989). Blue Print Reading Basics, New York, NY: Industrial Press Inc. Jensen, C.H., Hines, R.D. (2002). Interpreting Engineering Drawings, Albany, NY: Delmar Publishing Madsen, D.A. (2004). Engineering Drawing and Design, Albany, NY: Delmar Publishing

Credits: Writer: Will Renauld Lesson Editor: Donna E. Scribner Narration: Donna E. Scribner PLTW Editor: Ed Hughes Production: CJ Amarosa Video Production: CJ Amarosa Audio: CJ Amarosa Project Manager: Donna E. Scribner