Inventor 2015 2D sketch mode offset issue

[Anonymous]

There might not be many Inventor users here, but I imagine that there are certain things universal to most Autodesk products.  I'm having an issue when I enter a specific offset distance.  It doesn't seem to work well on circles or geometry that doesn't have perfectly horizontal or vertical sides.  Here's what I do:

1)  Go to Modify -> Offset
2)  Select the geometry
3)  Begin to stretch it and then enter a specific value
4)  Press Enter

I'll specify, say, 0.0625 and it will go to something like 0.06267 or 0.59xx.  There were a couple of shapes that had horizontal lines on the top and bottom that did fine.  However, circles and geometry that doesn't have horizontal or vertical lines seem to be a problem.

[JDMather]

Add a parametric dimension.

In Inventor you dimension (or add geometry constraints) to everything so that you know exactly what you have and you know exactly what will happen if you make any edits.

[Anonymous]

Thanks for the response.  I'm teaching myself and working on my first project; which is well on its way.  How do you add a parametric dimension?  Also, I'm designing a guitar which is comples, but not as complex as a lot of machinery.  I'm working on the pickups and made them a little too small.  So, I'm resizing them via "offset".  I haven't been using constraints.  I suppose I should learn a bit about that.

[JDMather]

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@Anonymous wrote:

....  How do you add a parametric dimension?.....

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Click dimension (or hit d on the keyboard) and select the two circles.

Before you develope an bad habits - I recommend you go through these -

http://home.pct.edu/~jmather/SkillsUSA%20University.pdf
http://inventortrenches.blogspot.com/p/inventor-tutorials.html

And of course, there are also the built in Learning Tools and Tutorials.

[Anonymous]

I tried that just now.  It wouldn't let me change the value.

[Anonymous]

OK.  I got it to edit, but it shrinks the entire geometric shape; not just the concentric circles.

[Anonymous]

I browsed through you PDF.  Looks very thorough.  I made the suggested changes to the preferences.  I'll reference other tips as needed.

[JDMather · Accepted solution]

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@Anonymous wrote:

OK.  I got it to edit, but it shrinks the entire geometric shape; not just the concentric circles.

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Of course you need to dimension the diameter of one of the circles, not just the offset.

Just like the real world out on the shop floor running the lathe (or milling machine).

Dimensions matter.

Othewise - you are not in control of your machine.

Simply double click on an existing dimension to edit.

[Anonymous]

Yes, I finally figured it out.  Thanks!