Dimension Notes

American National Standard Institute (ANSI)

• Establishes standards
• Not arbitrary rules

Why Dimension?

• Describes size
• Locate details

Basic Rules

• Should be convenient for the reader
• No calculation necessary
• No duplications

Dimension Line

• No closer than 3/8 inch from object line
• Lines and symbol inside extension lines if possible

Extension Lines

• Dark and thin
• Extend from object but 1/16 inch gap between object and extension line

Leaders

• Leader scale = Dimension scale
• Run at angle so it is obviously not part of object
•  1/4" tail
• Arrow if to edge, dot if to surface
• Cross as few lines as possible
• Any angle except horizontal or vertical
• Don't pass through corners

Linear Dimensions

• First, Big 3, H/W/D
• In between if possible
• Off view where detail is best describe
• Don't dimension from hidden line
• Locate from common corner
• Smallest dimension clostest to object
• No calcalation
• No doubles

Angle Dimensions

• Drawn at same angle
• Use degree symbol {%%D}

Circular Object Dimension

• ARC- part of a circle, dimension as radius
• Circle- always dimension {%%C}
• Cylinder- in side view
• Hole- shown where hole is

Finished Surface

• Check mark
• Shows finished surface