Integy has a Torque sensing set, that should just about eliminate that from happening, and it'll help you keep from overtightening screws going into plastic...Plus it comes with both SAE, and metric bits...Sweet set...
Here's a link to the set I'm refering to...
http://cgi.ebay.com/Integy-C22780-V-...742.m153.l1262
Hope this helps...