Mike, there are a lot of people here much more knowledgeable than me, but I will take a stab at this, given that it has happened to me more than once.
If I am understanding your question correctly, it seems you are concerned with filling the gap to the same diameter as the blank. I wouldn't worry about that, it is not going to be perfect and you're going to have to turn and/or sand once the gap is filled.
A few times I was able to save the piece that chipped out and just glue it back in place and continue. If I don't have the original piece, I put some shavings in the gap, but I don't try to fill the gap on the first pass. Then I drizzle in a little thin CA, hit with the accelerator and repeat. So in other words, I fill the gap a little at a time. I do this to try to minimize any voids that might form from filling the gap all at once. When the gap is filled, there will generally be a small mound of CA and shavings that needs to be cleaned up. I don't have a problem with that because it gives a little material to work with.
Once the gap is filled I clean it up with a skew or scraper. You can use sandpaper, but if you are close to the final dimension you risk taking off too much material in the undamaged areas as you squeeze the sand paper around the blank, and this will be particularly noticeable if the chip came out at one of the ends.
Kind of a long-winded answer. Let me know if I my answer is out in left field.
If this didn't answer your question, maybe post a picture so we can actually see what you are up against.
Chris
