I came across this thread while searching for something related to this issue. Sorry of someone has already mentioned the following but didn't read the entire thread.
As one of the first people who responded said, an impact driver would do the trick and, as someone else said, tapping the torx bit with a hammer usually works too. The first response may have been referring to the tool I'm mentioning but, if it does, someone may think he was referring to a pneumatic impact driver. You can get the benefit of both methods by using a manual impact driver as pictured below. I must have four or five of these things and they have saved the day (and make jobs easier) more times than I could possibly remember over the over 50 years I have been working on my machines. They're inexpensive too. Harbor Freight probably has ones just as good as anyone else's for next to nothing. You can use them with sockets and bits other than the Phillips head and flat screwdriver heads that come with them. As long as you can get a clear shot on the bolt, just a tap of a hammer on the end of the tool and you should be all set.