Geometric construction with Illustrator

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mikeblas

[H]ard|DCer of the Month - May 2006
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I have to cut a rounded hole to mount a latch in a steel panel. The hole is around a 0.75 inch square, and the radiuses at the corners are about a 0.885-inch circle. You can see the hole I'd like to cut on the first page of this PDF file: http://www.southco.com/resources/documents/e3.en.pdf

I don't have a tool to do this, obviously, so I need to make the hole freehand. I thought I might be able to use Illustrator to make a template, but it's not going so well.

I tried drawing a rounded rectangle with a width and height of 0.750 inches, and a radius of 0.4425 inches. That draws a circle. After fooling with it for a while, it appears that Illustrator draws the radiused corners by subtracting the radius from the corner of the square, then drawing a quarter circle at that point. This means the radius can't be as big or bigger than half the width of the shape; at that point, the shape just becomes a circle.

Then, I tried drawing a square and a circle. How can I get them positioned so their centers are exactly at the same point?

Assuming I do, how do I construct the shape so that I'm using the radiused corners from the cirlce an the sides of the square?

Thanks.
 
In case you still need this, here it is: drawing I'm sure there's a way to do it with Illustrator, but I have no idea how so I just made it with AutoCAD.
 
Thanks!

Yesterday, I downloaded a demo of TurboCAD and made the drawing there. The Deluxe (not Professional) version is only $70, so I'll probably buy it for whatever projects I need again.

But thanks for taking the time to help out!

I'll post a picture of the knob when I get it mounted into the boat. There's a double-tabbed 0.750 inch hole in the boat now, so I have to manually widen it to this shape for my new latch. With my template and my Dremel, I'm sure I'm alright...
 
I'd still love to learn how to do this with Illustrator, by the way. It struck me as ironic that I did it with TurboCAD in about 15 minutes even though I've never used it before (though I'm quite experienced with AutoCAD -- which has a substantially different user interface).
 
In Illustrator on a rounded rectangle you can adjust the corner radius while drawing the rectangle. While drawing the rounded rectangle keep left mouse button held and use your keyboard up/down arrows to adjust the corner radius.
 
As I guessed above, the shape I want to draw isn't a rounded rectangle -- at least, not as far as Illustrator is concerned.
 
Well with Illustrator you can just draw the 0.75 x 0.75 in square by selecting the square tool and clicking anywhere on the document, then for size enter "0.75 in" in both the width and height fields. Then make an ellipse with the width and height "0.885 in" and then go to Window > Align, then that will bring up the align dialog, the select the two objects and click the second align button and the fifth align button, and that will align the two horizontally and vertically. Then if you wanted to get fancy you could probably trim it somehow, but that's not really needed since you already have the lines you need. I hope that makes sense :)

EDIT: Acutally if you then want to trim it, select both the objects and click the crop button (on it should be on the "Pathfinder" tab in the same window as align).
 
Crop ends up deleting both of the shapes. Well, it merges the shapes in the wrong way, then sets the stroke to zero. If I reset the stroke to 1 pixel, I end up not having the shape I want.

Thanks for helping, though!

I ended up using my drawing from TurboCAD and printing it on an overhead transparency sheet. I Dremeled out the shape last night after coloring it in with a marker, and mounted the latch no problem. It looks great!
 
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