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Exploring Drafting
when a pattern of holes is machined in a round
part). Arrays may be created in rectangular or
polar arrangements with the Array command.
See Figure 7-18. A rectangular array is created
by entering the base point, number of rows,
number of columns, and the spacing between
rows and columns. The number of columns
and rows determines the number of objects in
the array. A polar array is created by specifying
a center point, the number of objects in the
array, and an angular value determining the
amount of rotation. Entering 360° creates a full
rotation of objects about the center point.
Mirroring Objects
When drawing symmetrical objects, it is
sometimes useful to create a mirror image.
This operation allows you to select an object
and make a mirror copy. This can save time
when you want to draw half of an object and
complete it by “mirroring” it. See Figure 7-19.
The Mirror command is used to mirror an
object. To use this command, the objects to be
accomplished with the Scale command. After
selecting the object to be scaled, the base point
and scale factor are specifi ed. A scale factor of
0.5, for example, would be used to reduce the
size of an object to one-half its original size.
Undoing a Command
CAD programs typically provide a
command that allows you to “undo” a previous
operation. If you enter an incorrect value for
a scale or move operation, for example, you
can reverse the action by using the Undo
command. This command typically allows you
to undo several preceding commands, one by
one. However, the commands must be undone
in sequence.
Redoing a Command
The Redo command is used to reverse
an action that was undone with the Undo
command. For example, if you move an object
and then use the Undo command, the object
returns to its original location. However, if you
decide that the object should be placed back
where you moved it, you can use the Redo
command to reverse the “undo” operation and
return the object to where it was moved. The
Redo command must be used immediately
after using the Undo command.
Erasing Objects
The Erase command provides a quick way
to remove unwanted objects from a drawing.
After you select the objects to erase, the
command automatically removes them from
the drawing. The Undo command can be used
to restore an object that has been erased
unintentionally.
Arraying Objects
An array of objects can be created by
orienting multiple copies of a selected object
in a pattern. This operation is useful when the
same object appears in multiple locations in a
regular pattern in the drawing (for example,
Original
object
A
Original object
B
Goodheart-Willcox Publisher
Figure 7-18. Arrays are created by orienting copies of
original objects in a regular pattern. A—Rectangular
array. B—Polar array.
Copyright Goodheart-Willcox Co., Inc.