Isometric View

Exploded Drawing

Section View

Assembly

Descriptive Geometry

Manipulating (rotating) picture planes (surfaces) in order to identify

• True size
• True shape
• True length
• True angle
• Intersection points
• Distances

True Length Lines

• If a line is parallel toa fold line in 1 view, it is true length in the next view

Point View

• You must first find a true length line
• Create a fold line perpindicular to the true length (TL) line

True Size Surface

• You must find TL of one line
• Create fold line perpendicular to the TL line to get the edge view (EV) of the surface
• Create fold line parallel to the edge view

Addaline

• Addaline allows you to skip a view when finding TL

Auxiliary Views

Auxiliary Views

• Sometimes you need more than three views to tell the whole story
• Secondary view shows true size and shape(TSS) of a surface that shows foreshortened in a;; traditional views
• A surface is TSS when its edge in the next view is parallel to the fold line

Tolerances

Tolerances

• Hold precise tolerances to insure the interchangeability of parts
• Process of determining the amount a dimension can vary from its theoretical size

Basic Size

• Exact theoretical size

Tolerance

• Amount dimension can vary from basic size
• Feature used to identify the geometry of a drawing being referenced

Limits

• Maximum and minumum allowable size

Allowance

• Limits where smallest clearance or largest interference occur

Tolerance Style

• Limits dimensioning
• Plus/ minus dimensioning(deviation)
• Symmetrical Dimensioning

MMC

• Max Material Condition-limit of a dimension where the maximum material is left on the part

LMC

• Least Material Condition-limit of a dimension where the least amount of material is left on a part

Type of Fit

Clearance Fit

• All Dimension combinations will produce clearance between parts(running and sliding fit)

Interference Fit

• All combinations of dimensions will produce a force fit

Transistional Fit

• Different combination of dimensions will produce different kinds of fits

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