2 trees a minute. 120 trees an hour. 1,000 trees in an 8-hour work day, per machine.
Science magazine estimates there's 390 billion trees in the Amazon alone. It would take 390 million days (a little more than a million years) for that machine to cut it down, if it was cutting every day for 8 hours a day.
If you had 30 machines cutting every day for 8 hours a day, it would take 35,600 years for them to clear the Amazon, assuming no trees grew back.
Google says slow growing trees take 20-30 years to reach full size, and that tree stumps do form sprouts that eventually turn into trees again.
You would need 35,000 machines like this cutting down the amazon rain forest every day, for 8 hours a day, to exhaust the Amazon's supply of fully-grown trees before they have a chance to grow back.
http://www.youtube.com/watch?v=Zz1q1L3UHiM