I have an electric corded drill and a 12-V cordless Black and Decker -
Firestorm. I use both drills for occasional household repairs. I mostly
use the cordless.

From time to time I break bits because the materials I am going through
might be too difficult to get through. I generally replace with Black oxide
bits. The 1/8" drill bit package I have indicates it's good for wood,
plastic and soft metal.

I'd like to know what types of bits I should be buying. Sometimes I do need
to go through a piece of metal. Most times I work with wood. Should I have
two sets of bits... one for metal the other for wood? Or, is there one type
of bit that is good for both?

Another question. This one about my cordless drill. It's a cheap model,
but serves my purposes. I find that even though I hand tighten the bit
receptor, occasionally the bit stops spinning as the receptor losses its
grip. It most often happens when I am going through denser materials. Is
this a drill flaw? I don't remember it happening to my electric drill with
the key tightening system. I doubt I can do anything about it, but thought
I pose the question anyway. Do better cordless drills have the same
problem?