Most of the drivers sold by RC airplane places are soft and round off. Try using #2 button head screws with a .050" driver and you'll see what I mean.

Search for hex drivers on Tower or the web. The really good drivers are usually found around RC car guys. They have aluminum handles, replaceable blades and are hardened. Normally, the blade is made from drill bit stock, the tip is ground on, then it is hardened. I have some red handled Dynamite brand and a few blue handled ones.

These guys aren't cheap. Most run from $5-$10 per driver or $30-$50 per set. They are quality. And I use lots of button head screws now. I haven't rounded off a .050" one in 5 years.

[link=http://www.duratrax.com/caraccys/dtxr0176.html]Duratrax[/link]
[link=http://www.integy.com/st_main.html?p_catid=161]Integy[/link]
[link=http://www.amazon.com/Machined-Hex-Driver-US-Set/dp/B0006O503M]Dynamite[/link]

The Dynamite set has solid aluminum handles. The Duratrax drivers have hollow handles.