Object snaps (Osnaps) are one of the handiest tools in AutoCAD. Without them, you would have a lot of trouble doing even the simplest dimension accurately. Before discussing how they are used, first think about what they are. Their name, “object snaps” means that they snap to objects, or more precisely, they snap to specific parts of an object. A line for example has 3 points that you can snap to: a midpoint and two endpoints. A circle has 5 points: a center and 4 quadrants. To use Osnaps effectively, you must know what points an object has that you are able to snap to.
There are also some Osnaps that are not precise. These allow you to snap to (sometimes) arbitrary points along an object. These would include nearest, tangent, perpendicular and to some extent, intersection.
There are two different ways of working with Osnaps; in running mode or invoking them individually as required. Running Osnaps mean that certain ones are turned on and running in the background. This means that they are available when needed in the middle of a command.
Sometimes you may need one Osnap that isn’t one you have selected in running mode. In this case you can turn it on for one-time use. There are a few ways of doing this: you can select the icon for the Osnap you need, you can type in the 3 letter shortcut, or you can bring up the Osnap dialog box and turn it on (‘OS), or even shift+right-click and pick from the menu. I recommend learning the 3 letter shortcuts and typing them in when required. This is generally the fastest way to get your Osnap on, plus it doesn’t leave it on if you don’t need it afterwards. Having the icons up your screen works, but takes up valuable screen area. Try each method and see which one works best for you.
In most cases you do not want to turn on all the osnaps while drawing as you could accidentally snap to a point you don’t want. For example, the endpoint and a perpendicular point could be very close – so you need to be careful when using perpendicular.
Below is the Osnap dialog box with a detailed listing of how each one is used.
|TT||TEMPORARY TRACK POINT|
|–||M2P||Middle of 2 points|
The Osnap toolbar is only available when you are in the AutoCAD Classic Workspace. You will see the icons when you Shift+Right-Click while in a command.
The 3 letter shortcut is in bold in the list above, notice that it is the first 3 letters of each Osnap.
Also note the Osnap symbol beside each setting in the image of the dialog box above. These will be visible on your screen as the osnap becomes active.
LISTING OF OSNAPS MODES
Command: L LINE Specify first point: MTP
First point of mid: <PICK> Second point of mid: <PICK>
Specify next point or [Undo]: (Select point or enter to end)
OTHER NOTES ABOUT OSNAPS:
Osnaps are only available when you are currently in a command.
Toggle Osnaps on and off by using the F3 key. If you do not have any Osnaps on in running mode, the F3 key will invoke the Osnap dialog box.
Get into the habit of working with the same 2 or 3 Osnaps in running mode whenever you are drawing. The more consistent you are, the easier it is to keep track off while working.
When dimensioning, you must be VERY careful where you are snapping to. Make sure that you are not using the nearest, perpendicular or intersection Osnaps unless you specifically require them. Below is an image that shows a common mistake of dimensioning to another dimension line and not the object. Often you will catch this if your measurement is an odd number (should be 11 in the example below).
If you have a lot of objects in one area, and need a particular Osnap, use the TAB key to cycle through all available Osnaps in the area. As you hit the TAB key, you will see that the Osnap location changes and AutoCAD highlights the object you would snap to.
Zoom in when in doubt. Make sure that you are snapping where you need to. Snapping to the wrong part can cause catastrophic events.
If you want to invoke the Osnap dialog box while in the middle of a command, type in ‘OS at the command prompt. You can then make your changes and then continue with the command.
If you want to change the appearance of the Osnap indicators, such as size or color, bring up the Osnap dialog box and pick on the Options button on the Osnap Dialog box).
On the left side of the dialog box, you can set the ‘look’ of the Osnaps when you are using them.
The Marker, Magnet and Snap Tip should be left on. Marker shows the active osnap. Magnet ‘snaps’ you into position when you are near. The Snap Tip is a small text box telling you which osnap is current. Leaving the aperture box off, makes it easier to see the snap points.
The Marker Size is a matter of personal preference, but the default seems good to me.
The color of your Osnap might need to be changed depending on the color of the objects you are working with or screen background color.