what size would you make a hole for a stick to be put in?

sorry for not knowing how to word this well.

so im making a project where you can swap heads on a body and i want to know what size i should make the stick and the whole. Last test had the hole and stick be identical and that didn't work because of how tight it was. I want to know what size increase i should make the hole.

btw im using blender for this