AutoCAD 2012 grid question

[rbudd22]

I am looking to create a grid that is 10"x10" and has .25" spacing for a project I am doing with my students. We have been using a very old CAD software program and I am not entirely used to 2012 yet. I only want students to see a 10"x10" area to draw in. I found where to change grid spacing but I haven't figured out the other half. Thanks for your help!

[ger21]

Look up the LIMITS command in the help file. The grid will still be infinite, but you can only draw in the specified area. You might want to draw a border on a special layer and lock it, so it's easier to see the extent of the limits.

[rbudd22]

Thanks for your help. It worked perfect! My next question is I am looking to join the corners of overlapping rectangles in 2D. When I used AutoSketch8 I used to use the union tool to do this but it doesn't seem to work the same in AutoCAD 2012. I've attached a screenshot of what I got. Thanks again!

[ger21]

My next question is I am looking to join the corners of overlapping rectangles in 2D

I don't understand what you want to do?

[rbudd22]

I used the rectangle tool to draw four different rectangles with the ends overlapping. I now want to "join" the corners and have it so you see a square inside of the outside square without the corners intersecting. I've attached a screenshot showing what it would look like after using the command. I have to draw separate rectangles for a reason and then join the corners based on a CNC machining process or I would not be trying to do it this way. Thank you again!

[ger21]

So you want to "center" the smaller one inside the larger? I don't believe there's a command to do that.

What I've always done, is draw a line from corner to corner in each rectangle, and then move one, using the midpoint of one diagonal to the midpoint of the other.

[ger21]

OK, Google just found a quicker way.
Draw your 2 rectangles.
Select one and use the Move command. (I right click to access the command)
Shift-Right Click, and choose "Mid Between 2 points", and pick diagonal corners of the rectangle.

Shift-Right Click again, and choose "Mid Between 2 points", and pick diagonal corners
of the destination rectangle, and it will be centered.

I'm not sure why you can't just use the offset command?

In your example, nothing is actually "joined"? If you can you explain exactly what you're doing a little better, I might have a better solution.

[rbudd22]

My middle school students construct a marble maze project using our CNC machine. I have them draw .25" thick rectangles within their 10"x10" grid to act as walls. Our CNC machine then uses a .25" end mill bit to mill out grooves for their walls .125" deep wherever they have rectangles. We create a tool path so that the end mill bit stays in the center of each rectangle.

In the past when students draw in all of their rectangles in CAD, I have had them overlap the ends by .25" so that they could go back and union/join their rectangles. This way the CNC machine will mill out their walls continuously and not start and stop on each wall.

[ger21]

I think you'll need to teach them how to move them and use the trim command, and if you need all the lines joined, use PEDIT with the Join option.

[rbudd22]

Thank you for all of your help. It seems odd to me that AutoSketch would have a feature to "union" that AutoCAD does not in 2D. I'll try to see what I can do with my students here and if we are able to make that work. Thanks again.

[ger21]

I'm still not sure if I understand what you want to do.
The Union command does work in 2D, if you convert your rectangles to regions first. (Just type REGION, and select them).

This is the result of the union command.

[JMaeding]

To do what you want, you must understand that the rectangle command draws what acad calls a polyline. It draws a closed polyline to be specific.
So to remove portions of a pline, you should trim them out. then you will have separate pieces that you can join with the pedit command.
Not sure if you care if the end result is a pline. if not, just explode the plines and then you have simple lines that are esy to manipulate.