I took off a hollow core interior door to paint it. Very thin coats (this is only the second time it's been painted since contractors built house. I know they only sprayed 1 very thin coat). Now the door doesn't seem to fit as well. I did new hinges -same size just different color. I know I can plane it for better fit but I want to know why the door doesn't fit right back in. The new coats of paint are not too thick so it's not the paint job. Ideas? I have more doors to redo so I want to avoid this problem again.
The new coats of paint are not too thick so it's not the paint job.
and this is a common misconception. Yes, it looks like the paint is negligibly thin but it actually adds up. When a door is constructed it has size that allow for painting it once, maybe twice, and then a new layer of paint will prevent it from closing.
You should have cleaned the previous paint off the door edges.