Hello there, I have an old house with an unused 240V 40amp breaker. I want to run wire from the panel to some shop equipment that only needs 120V. The breakers are pretty old so replacement of one isn't going to happen. Is there a way to only use 120 of the 240?

Your help will be appreciated.

No, not with a 40A breaker. You cannot have standard 120v receptacles on anything other than a 15 or 20 amp breaker.

About the only thing you can do it run a 40A circuit to a small sub-panel. This will give you several new spots for new circuits.