Phillips Flat Undercut Head Thread Cutting Screws

Phillips, Flat Undercut, Thread Cutting Screws. Thread-Cutting Type-F threaded screws are used in heavy gauge sheet metal, aluminum, zinc and lead die castings, cast iron, brass and plastic. In stainless steel, material into which the screw is to cut threads should have a lower hardness by 10-20 Rockwell hardness. Flat undercut heads are used when a flat head is desired on shorter length screws.