BigByte Drafting - AutoCAD Tips & Tricks

AutoCAD LT Tips and Tricks

Site Map

Index
   AutoCAD LT
      Tips & Tricks
         Selection Sets
         Stretch Command
         DXFIN Workaround
         Multiple Copy Bug
         Third Array Option
      DIESEL
     System Variables
     Custom Menus
   Visual Basic
   Resources on the Net
   Contact BigByte

Knowing and understanding what you are drawing and how it will be fabricated is the most important concept for a draftsman to grasp, however like any trade, knowing how to use your tool to its maximum efficiency is also very important. On this page I describe some of the techniques I have learnt over the years to increase my drafting efficiency.

Manipulating Selection Sets

Since every AutoCAD editing command begins with the prompt SELECT OBJECTS: any technique that speeds the selection of objects is going to increase your overall efficiency. At this prompt you can respond with any of the following options:

Window/Last/Crossing/BOX/ALL/Fence/WPolygon/CPolygon /Add/Remove/Multiple/Previous/Undo/AUto/SIngle

Most of these options are fairly self explanatory. The difference between a Window and a Crossing is that Window selects only entities contained by the selection rectangle whilst a Crossing selects all entities within AND touching the selection rectangle. A Window selection method is the default action when you pick an empty part of the screen and drag the pointer from left to right. Dragging right to left will form a Crossing selection method.

My favourite option is the Previous keyword. This rather obviously access the previously created selection set but did you know that the EXPLODE command creates a selection set of the individual entities making it very easy to than change them to a different layer (for example)

A less known trick to use the SHIFT key whist selection entities to remove them from a selection set. For example, it may be quicker to select a group of entities with a Window or Crossing option and then remove one of two entities from the selection set by holding down SHIFT and picking them again.

STRETCH Command

On of the most powerful command, in my opinion, is the STRETCH command. The Users Guide says that you must use the Crossing or CPolygon (crossing polygon) method. Attempting to select more objects after the initial selection will cause the command to fail. Also attempting to remove any more that ONE entity from the selection set will also result in nothing happening.

So heres the tip. Create a selection set of the entities that you DON'T want to stretch using the SELECT command. Issue the STRETCH command and select using Crossing or CPloygon method, then type "R" (for Remove) [ENTER] and "P" [ENTER] to remove the Previous selection set. It sounds complicated but it isn't and you will find the STRETCH command much more useful.

DXFIN Work-Around

With the release of AutoCAD LT '97 (and R14) Autodesk, in its wisdom, decided that we would not be able to import a post R12 DXF file into an existing drawing. Attempting to do so will result in the following message:

AutoCAD LT cannot DXFIN this file. You can DXFIN the file into a new drawing, save the drawing, and use INSERT* to include the entities from that drawing into the current drawing.

On work around is to work with R12 DXF files, however this means that many R14 entities such as MTEXT, LWPOLYLINES etc will be converted to R12 compatible entities.

Another work around is to work work with R14 DXF files, but before importing them open the DXF file in a text editor and search for the $ACADVER variable in the header section. Changing the value of the next line from AC1014 to AC1009 tricks LT into believing the DXF file is R12 while still retaining R14 entities.

***WARNING***WARNING***WARNING***
Autodesk has informed me that technique has the potential to corrupt a drawing if the DXF file has interobject references. Exactly what an interobject reference is I do not know and I have never had any problem, but be warned!

Multiple Copy Bug

Be warned that attempting to make more than sixteen (16) copies of a selection set will cause a Fatal Error when the command is ended with the ENTER key, space bar or right mouse button. This can be avoided by ending the command with the Esc (CANCEL) key.

Undocumented Third Array Option

There is another little known and undocumented third option of the array command. While most AutoCAD Users are familiar with the Rectangular and Polar options, you can create a Circular array ("C"). It creates a Polar like array but differs in the fact that it will prompt the user for the angle between objects verse the angle to be filled.

Command: ARRAY Select objects: 1 found Select objects: Rectangular or Polar array (R/<P>): C Base/<Specify center point of array>: Angle between items (+=ccw, -=cw): 15 Number of items or -(degrees to fill): 4 Rotate objects as they are copied? <N> Y