Dimensioning Standards…..Why are they needed? To give manufacturers and part fabricators the information they need to create complicated parts. AMERICAN NATIONAL STANDARDS INSTITUTE Organization that oversees products, services, drawing plans, etc
How are they read? Working Drawing Appropriate units of measure Inches Millimeters Decimals recommended over fractions of an inch. Two common systems
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Importance of standards!
Unidirectional System
Aligned System
Standard Spacing 1/4” 1/4” 3/8” Dimension Lines Extension Lines 1/16” GAP Dimension Lines Extension Lines
Arrowheads Arrowheads on dimension lines Touch extension lines and are drawn to specific proportion Length 1/3 of Arrowhead Length Can be slightly curved
Dimension Placement Whenever possible, dimensions should be placed between the views to which they relate. Avoid Preferred
Extension Line Conflict Line conflict should be kept to a minimum. Place smallest dimensions closest to the object. Avoid Preferred
Hidden Lines Should not be used for dimension unless there is no other way. Avoid Preferred
Circles and Curves Circles/curves are dimensioned in a number of ways depending upon diameter/radius TYP. = Typical unless noted otherwise TYP.
Hole Notes Special symbols simplify dimensioning multiple or complex holes Cutting Plane Line Section Lines