I had a tree I needed to take down on my property of about 10" to 11" diameter.
Though I wouldn't recommend using a small ax of this size for the project, I did it to test it out. It was a lot more effort than I'd care to repeat, but it did the job without any damage to ax or edge.
In the future, however, I'd use one of my larger Gransfors Bruks axes for anything over 6" or 8".
Hope that helps some.