I have both these corals in my tank too. I do not let them touch as they are both classified as "aggressive corals" as far as I know. I think they will sting each other. I try to use the general rule of a few inches in between my corals.
yes, hammer corals are very aggresive with long sweeping tentacles just looking to damage other corals. I have one "small" hammer coral that has such long sweepers that 6 inches wouldn't even be enough.