Imperial Pan Phillip Screws

Pan head screws have a broad head with rounded edges -- the shape of an inverted frying pan. They are made in a variety of sizes and lengths and with various styles of threading. These types of screws are often used to secure machine parts, particularly when the components are made out of metal, but are used for many other applications such as woodworking. The slot on a pan head screw is typically a Phillips- or crosshead-slot, although other slot types are used as well

Round head Screws have a half round head sits higher than pan heads and button head screws

Phillips Head is an improvement to the slotted screw; cross-shaped grooves that do not extend to the edge of the screw head accept a Phillips-head screwdriver. These heads, which have a slight circular shape where the slots cross, provide a larger mating surface between the screw and the screwdriver, which minimizes wear and helps prevent slipping.

Machine screws have finer threads than wood screws. They are designed to be used in conjunction with a nut or tapped hole.