At 14 months he is all about action/reaction. He wants to know that this is not acceptable behavior, he doesn't understand that it hurts just yet. You just need to be firm and consistent. He probably won't understand time-outs until he's closer to 2. You should just tell him NO HITTING very firmly, and remove him from the situation. He will get it eventually. My two boys were both hitters, and biters to some extent. My 3 year old grew out of it, and my 17 month old somewhat understands that what he's not supposed to do, but he does it anyway, just to double check :).
What you probably shouldn't do is hit him, even as a tap, because it's telling him that hitting IS okay in certain circumstances, and he will continue to hit.
Good luck!