I have 4 cpvc female adapters I need to thread onto a male threaded shower diverter. How do I do this and what happens if I over tighten them

Just screw the adapter on then glue pipe to adapter. Use reasonable effort when screwing adapter on. Not really necessary but if it make you feel better, either wrap threads with Teflon tape or coat with pipe thread joint compound. Contrary to popular belief these are not sealers. They are lubricants. They enable you to tighten fittings with less effort.

Ron,
Plastic female adaptors can be problematic when trying to couple with metal fittings, and, certain types of plastics do not react well with liquid pipe joint compounds; check with the cpvc or compound manufacturer for compatibility. We avoid using plastic female adapters, they can split rather easily while trying to firmly tighten them. When there is no choice and we have to use a plastic adapter, we'll tighten a suitably sized stainless steel clamp on the adapter before assembly. ...
Oatey Corp makes liquid pipe joint compounds ( they acquired Hercules Chemical ) that will seal & bridge small gaps, threads, and fitting imperfections to help make a water tight joint, Google Hercules Grip......

Hi Ron

Yeah, if you have the all plastic female adapter, return them and pick up the metal/plastic hybrid CPVC female adapter... only way to go here! They are available at almost all plumbing supply stores. See image:

Attachment 48273

Plastic (CPVC) female adapter should never screw onto metal male adapter as the CPVC female adapter will eventually crack. It should be the other way: Male CPVC into female metal inlet.

I agree with Mark's advice: return what ever you already purchased and get the transition adapter Mark posted. That is the best, and the safest, way to go.

Milo