Sprocket Assembly

We were given a team project that required me along with a partner to model and assemble the parts of a sprocket assembly, the following are images of the result.

Descriptive Geometry

Discriptive geometry is a way of manipulating picture planes in order to identify:

• True Size
• True Shape
• True Length
• True Angle
• Intersestion Points
• Distances

True Length Lines

• If a line is parallel to a fold line in one view, it is true length in the next view.

Point View

• Must first have true length line
• Fold line must be perpindicular to the true length line

The Add-A-Line Method

The addaline method is a faster method due to the fact that it allows you to skip drawing a view that you would usually have to draw in order to find a true length line.

Auxiliary View Notes

• Sometimes 3 views aren't enough to show all that you need.
• Auxiliary views are secondary views used to show true size and shape (TSS) of a surface that is not well represented in a traditional view.
• A SURFACE IS TSS WHEN ITS EDGE IN THE NEXT VIEW IS PARALLEL TO THE FOLD LINE.
• Skip a view, measure back.

Tolerance Notes

• Necessary to hold tolerances to insure interchangeability of parts.
• Tolerance is the amount a dimension can vary from its theoretical size.
• Basic Size is the exact theoretical size of a dimension.
• Features are used to identify the geometry being referenced
• Limits are the minimum and maximum allowable size.
• Allowance is the limit where smallest clearance or largest interference occurs.

Styles:

• Limits Dimension
• +/- Dimension
• Symmetrical Dimension

MMC = maximum material condition (limit of a dimension where the maximum material is left)

LMC = least material condition (limit of a dimension where the least material is left)

Fit:

• Clearance fit = All dimension combinations produce clearance between parts.
• Interference fit = All combinations of dimensions will produce a force fit.
• Transitional fit = Different combinations will produce different fits.

Dimension Notes

• Height, Length, Width
• Dimensions are drawn for the convenience of the reader.
• No calculations should be necessary.
• Do not double dimension.
• 3/8 in. from the object line
• Don't dimension to hidden lines
• Smallest dimension closest to object

Leaders

• Leader Scale = Dimension Scale
• Arrow to an edge
• Dot to a surface
• Not horizontal
• Not vertical

Ordinate Dimension

• Uses distances via (x, y)
• Command = UCS, MOVE

Counterbore

• Used when a bolt needs to sit flush with the level surface.

Countersink

• Allows a screw to sit flush with a surface.