I need to calculate contact stress of a ball bearing in a groove.
Let's assume a ball with diameter of 1.5mm, a groove with a large diameter of 7.5mm. it's smaller diameter is 1.55mm but it's hollow, so according to this it should have a minus sign.

We'll end up with equivalent radii R and r such that omega is smaller than 1. Can't say if I need a coffee break or not but I calculated it twice automatically and by hand once.
Is this omega a check if your radii make sense? Or what is it?
Can't find in other literature why I should care about this fucking ratio anyway