So i'm trying to create a slot in a solid object, into which I can insert another object later, but need to allow some "slop" space in the process...

For example, the rectangle is my main object, and the ring shown is the "later-to-be-dropped-in" widget....

My process has been to create both objects, move them onto each other in position, then do a "combine/subtract", to end up with my needed block shape..

Here's the problem.. I don't have the needed .01"-.02" space needed to allow clearance for later implimentation..

I was trying this by simply 'oversizing" the ring by .01" (prior to doing the cut), but realized than when I went back to resize it properly, SW passed the new sizes all the way thru the assembly, so the final product now has no slop space!  (darn those engineers who thought so far ahead!)....

What's the common method of doing this?