Creating blow-up details

Here is a step by step process for creating a "blow up detail" in paper space. This is one method that works well for civil drawings where you need a circular shaped, larger scale view.

1. In model space, draw a circle around the area you want to blow up. Preferably an even number radius.
Example 75' radius circle
2. Divide the circle radius size by the horizontal scale, this gives you the viewport circle size.
Example 75/100 = 0.75
3. Next, determine the scale for the detail blow up, and divide the horizontal scale by this value
Example: if you want a 20 scale detail, so divide 100/20 = 5.0
4. Multiply the answer in #2 by the factor in #3. This is the 1:1 viewport size in paper space.
Example 5.0 * 0.75 = 3.75
5. Switch to your layout and draw a circle. Use the size calculated in step #4
6. Convert this circle to a viewport, using the MVIEW command, Object option.
7. Change to model space inside this new viewport and perform a Zoom Center, using the center of the circle in model space as
the center point, and using a scale factor that equals the scale you chose in step 3.
Example: Zoom;C;1/20XP
8. At this point, the viewport will show you exactly what you circled in model space. Switch back to paper space, and lock the viewport.