POWERHOKI Plus, they are the ideal self tapping screw. They are commonly made of steel or brass. Like other fasteners, machine screws are also made with coatings -- brass, copper, nickel, zinc, cadmium, and galvanized -- that help deter rust. Machine screws are blunt-ended screws used to fasten metal parts together. Self-tapping screws of the round head variety are used for heavy-duty work with thick sheet metal and are available in diameters from 1/4 inch to 2 inches and in lengths from 1/8 to 3/4 inch. Partial-tapping round head screws have finer threads; they can be used in soft or hard metals. For light work, lead, plastic, or fiber plugs (called anchors) can be used to hold screws.|Lorong Waktu 3