LEARNING OBJECTIVES

       After completing this lesson, you will be able to:

      1. Understand Object Snap.

      2. Use Running Object Snap.

      3. Use the Zoom options to view the Drawing.

      4. Change the Drawing Limits.

      5. Select the Units of Measurement and Precision.

LESSON 4

Object Snap

      In Lesson 3 you learned about Increment Snap. Increment Snap enables the cursor to move in an incremental movement. So you could say your cursor is “snapping to increments” preset by you.

      Now you will learn about Object Snap. If Increment Snap snaps to increments, what do you think Object Snap snaps to? That’s right; “objects”. Object Snap enables you to snap to “objects” in very specific and accurate locations on the objects.

      For example, the endpoint of a line or the center of a circle.

       How to select from the Object Snap Menu

      1. You must select a command, such as Line, before you can select Object Snap.

      2. While holding down the shift key, press the right mouse button. The menu shown below should appear.

      3. Highlight and press the left mouse button to select an Object Snap.

       The following Object Snaps will be discussed in this Lesson:

      Endpoint, Midpoint, Intersection, Center, Geometric Center, Quadrant, Tangent and Perpendicular. Refer to their descriptions on the next page.

      The remaining Object Snaps will be discussed in future lessons.

       Object Snap Definitions

      Object Snap is used when AutoCAD prompts you to place an object. Object Snap allows you to place objects very accurately.

       A step-by-step example of “How to use Object Snap” is shown on the next page.

      Note: You may type the 3 bold letters shown rather than select from the menu.

ENDpoint	Snaps to the closest endpoint of a Line, Arc or polygon segment. Place the cursor on the object close to the end and the cursor will snap like a magnet to the end of the line.
MIDpoint	Snaps to the middle of a Line, Arc or Polygon segment. Place the cursor anywhere on the object and the cursor will snap like a magnet to the midpoint of the line.
INTersection	Snaps to the intersections of any two objects. Place the cursor directly on top of the intersection or select one object and then the other and Autocad will locate the intersection.
CENter	Snaps to the center of an Arc, Circle or Donut. Place the cursor on the object, or at the approximate center location and the cursor will snap like a magnet to the center.
Geometric CEnter	Snaps to the centroid of any closed polylines and splines. Place the cursor anywhere on the object and the cursor will snap to the centroid of any closed polyline or spline.
QUAdrant	Snaps to a 12:00, 3:00, 6:00 or 9:00 o’clock location on a circle or ellipse. Place the cursor on the circle near the desired quadrant location and the cursor will snap to the closest quadrant.
TANgent	Calculates the tangent point of an Arc or Circle. Place the cursor on the object as near as possible to the expected tangent point.
PERpendicular	Snaps to a point perpendicular to the object selected. Place the cursor anywhere on the object then pull the cursor away from object and press the left mouse button.

       How to Use Object Snap

      The following is an example of attaching a line segment to previously drawn vertical lines. The new line will start from the upper endpoint, to the midpoint, to the lower endpoint.

      1. Turn off SnapMode, OrthoMode and Object Snap on the Status Bar. (Gray is off)

      2. Select the Line command.

      3. Draw two vertical lines as shown below (they don’t have to be perfectly straight).

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