Learning to fight with a tomahawk?

I've recently become interested in learning to fight with a tomahawk. In learning about my ancestors...it was apparently a favored tool and weapon of choice through North America. I'm already reasonably proficient with a knife...and I don't do a bad job with my mitts either. But I wanted to expand and learn. So I wanted to know if the tomahawk was still a viable close quarters weapon? Can I use it effectively against someone who was attacking me with something like a machete?