Part 2
Module 8: Object Snap
Learning Outcomes
- Describe object snap, AutoSnap, and manual object snap modes.
- List the object snap modes for a line, a circle, and an arc.
- Apply the OSNAP command to set the object snap modes for AutoSnap.
- Describe how to enable and disable object snap and its importance when creating drawings.
- Use object snap to complete drawings.
Object Snap
Object snap allows you to immediately locate and attach to predefined object snap modes (locations) on existing drawing objects. All drawing objects have at least one object snap mode. In this module, the object snap modes for the drawing objects line, circle, and arc are taught. Many more will be taught throughout the AutoCAD 2D book.
Using object snap allows you to draw quickly and accurately using the existing geometry in the drawing. This is done without having to know the coordinate locations of those objects. Object snap is one of the most important features in any CAD system.
Study Figure 8-1, 8-2, and 8-3. They show the object snap modes and their locations for a line, a circle, and an arc. A line has 3 snap mode locations that can be snapped to while circles and arcs have 5 each. When requested, AutoCAD can find and snap to these exact locations.
AutoSnap
AutoSnap is a visual aid to help you see and use object snap modes (locations) more efficiently. It allows you to set the object snap modes that AutoSnap will find automatically when object snap is enabled. Object snap can be enabled or disabled anytime by pressing F3. While a command is active, AutoSnap displays a marker and a tool tip when the cursor is moved over an object snap mode location that it has been set to find. In Figure 8-4, AutoSnap is indicating that it found the endpoint of the line. Note that the Graphic cursor does not have to be located exactly at the endpoint of the line. It only has to be close.
Geometry Lesson: Finding the Center of a Square or Rectangle
Using geometry, the center of a square or a rectangle can easily and accurately be located without knowing its size or doing any math. To do this, either one of the following methods can be used.
Method 1
Step 1
Draw a construction line between any two diagonal corners by snapping to the endpoints.
Step 2
The midpoint of the construction line that you inserted in Step 1 is the center of the square or rectangle.
Step 3
In this step, a circle is inserted at the midpoint of the line. The circle is located exactly in the center of the square or rectangle.
Method 2
Step 1
Draw a line between the midpoints of two opposite sides of the rectangle or square.
Step 2
Draw another line between the midpoint of the other opposite sides of the rectangle or square.
Step 3
The midpoint of either line and the intersection of the two lines is the center of the rectangle or square. Actually, one line would have been enough to find the center.
Geometry Lesson: Using Construction Objects
The best way to construct most drawings is to draw construction objec