When drilling the holes for the rivets, one must drill them a bit oversize to make up for expansion when the rivets are set. The male rivet presses into the female rivet causing it to expand. If the side the male rivet is on is not drilled a tad oversize, well, it's gotta go somewhere. As you found, it usually cracks the male side scale.
Also, most knife supply businesses (like Jantz) have a neat little tool for sale. It is a step drill sized to drill the right size hole into the scale so the rivet head mounts flush. You don't need to go through a bunch of trouble to drill that hole in the scale and have it perfectly centered.
I really enjoy putting the knives together, said the man that has had a beautiful Damascus blade just waiting to have a set of very curly maple scales installed for over 3 years. I guess I wouldn't be doing anything with that knife if I wasn't delaying working on it.
John