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.
Since hollow core doors aren't made of the finest materials, is it possible that even your minimal amount of paint caused swelling? I could imagine that even just a bit of swelling over a 30 inch door width could cause it to jam.