Hillman Round Head Machine Screw, 8-32 x 1/2 In. Machine screws are designed to fasten metal parts together efficiently, either by using nuts or by screwing directly into a threaded receptacle. The length of the fastener is measured from the underside of the head to the tip of the screw, ensuring precise sizing for your projects. For optimal fit and performance, it is to pair these screws with nuts that have the same finish and threading. Model Number: