Square head set screws, also known as jack bolts, are fully threaded fasteners with a square head and most commonly, a cup point, though other types of points are available. Square head set screws are manufactured from alloy steel for maximum strength, as well as high resistance to galling, wear and fatigue. They have a large wrenching area that provides positive gripping for a hand wrench. They are ideal for holding pulleys, collars, and other machinery shafts where fine adjustments are necessary. Dimensional specifications are governed by ASME B18.6.2.