The bottom edge of the attached part is an arc. I need to reduce the radius of the arc, moving the bulge further up the face. I need the top of the new arc to be .5" from the top of the current arc (which won't be there anymore after the modification); I think this means the new arc should have a radius that's .5" greater than the current one. I've drawn an arc approximately where the new one should be (just eyballed it).

1. How do I draw an arc with a radius that's precisely .5" larger than an existing one?

2. Is it possible to edit the existing arc instead of drawing a new arc?

Thanks.

PS - Sorry if this posts twice. The first time I clicked "Post" the screen just went blank and the post didn't show up in the forum.