Phillips Drive / Zinc Plated / Fine Thread. Round head machine screws have a semi-elliptical top surface and a flat contact or bearing surface. Machine screws are most often used with a nut as a means of tightening unless they have a pre-threaded hole with the exact thread pitch. These screws are most commonly offered in smaller sizes. Other types of machine screws sold at NutsandBolts.com are: phillips flat head machine screws
, stainless steel flat head machine screws
and stainless steel round head machine screws
. Phillips head machine screws are the most recommended type of drive. A phillips drive offers more control and less slippage.