Tek 5 screws are the way to go. The longer drill bit tip is the trick to have them drill and not break off. I use these cheaper ones from eBay and they have worked great. Drill way better than the Homedepot ones with out the drill tip getting dull. I'm about halfway through the 450 count bag and have not broken one yet. Almost all were through 1/4" steel.
Lot of (450) indented hex washer head self-drilling screws. These zinc plated fasteners are 12-24 thread and are 1-1/4" in length with a 5/16" hex. These screws feature a #5 drill point tip and are designed to drill through steel up to 1/2" thick.