A Machine screw has a cylindrical shaft, threaded its entire length, and fits into a nut or tapered hole. Several different head styles are offered. Round Combo are the same as round head except for the option of using either a slotted or Phillips screwdriver. A pan head screw protrudes above the surface of the material to be fastened. Flat head screws are countersunk into the material for a smooth surface area. Flat undercut heads are supplied to provide larger usable thread. Head height of undercut screws is approximately two-thirds that of standard screws. Drive depths are reduced proportionately.